3.73's went in today!

[Mark42]

Got the 98 Firebird back from the shop. The Eaton TrueTrac and 3.73 gears were installed. Now there is a 500 mile break in period and its driving me nuts I can't hammer the gas! But I did notice that the car went right up my snow covered driveway where it couldn't do it two days ago with the old open rear.

There is a little noise from the rear when "feathering" the throttle, but under load and steady cruise its quiet. The shop said it should get quieter as it breaks in, but it won't be as quiet as if he installed OEM GM gears.

Also, as is to be expected, the speedo is off by quite a bit. Especially seeing as the car went from 3.08 to 3.73. That will get fixed as soon as I can hook up with SSP.

Right from the start I can feel the difference the 3.73's make, even with modest acceleration.

The best part was the shop (Steves Trans Repair, Stillwater, NJ) quoted me $300 as their standard labor charge for a gear change, pending any problems or extra parts. Well, after installing the parts the owner took the car for a drive, then put it back on the lift and took it apart to change the pinion depth to get a better wear pattern and reduce noise. I was seeing $$$ flashing before my eyes as he worked on it all day. In the end, the labor bill came to $380.00. Can't complain. A real Christmas gift!

I noticed a poster of the Eaton TrueTrac on the wall. Steve thinks their the best posi for street cars, so I was thrilled to hear that! He has two 1/4 mile cars in the bays being built for clients. I'll let this guy work on my car any day.

Followed the break in instructions for the Ring & Pinion gears... Drive for 20 minutes to heat it all up, then park and let it get stone cold before use again. Right now its in the "stone cold" stage.

Can't wait until the speedo is adjusted and gears broken in!

[mc73nova]

Got the 98 Firebird back from the shop. The Eaton TrueTrac and 3.73 gears were installed. Now there is a 500 mile break in period and its driving me nuts I can't hammer the gas! But I did notice that the car went right up my snow covered driveway where it couldn't do it two days ago with the old open rear.

There is a little noise from the rear when "feathering" the throttle, but under load and steady cruise its quiet. The shop said it should get quieter as it breaks in, but it won't be as quiet as if he installed OEM GM gears.

Also, as is to be expected, the speedo is off by quite a bit. Especially seeing as the car went from 3.08 to 3.73. That will get fixed as soon as I can hook up with SSP.

Right from the start I can feel the difference the 3.73's make, even with modest acceleration.

The best part was the shop (Steves Trans Repair, Stillwater, NJ) quoted me $300 as their standard labor charge for a gear change, pending any problems or extra parts. Well, after installing the parts the owner took the car for a drive, then put it back on the lift and took it apart to change the pinion depth to get a better wear pattern and reduce noise. I was seeing $$$ flashing before my eyes as he worked on it all day. In the end, the labor bill came to $380.00. Can't complain. A real Christmas gift!

I noticed a poster of the Eaton TrueTrac on the wall. Steve thinks their the best posi for street cars, so I was thrilled to hear that! He has two 1/4 mile cars in the bays being built for clients. I'll let this guy work on my car any day.

Followed the break in instructions for the Ring & Pinion gears... Drive for 20 minutes to heat it all up, then park and let it get stone cold before use again. Right now its in the "stone cold" stage.

Can't wait until the speedo is adjusted and gears broken in!

Glad to hear it worked out for you. I told you, Steve is a great guy and he is extremely reasonable.

[Mark42]

Thanks for the reference! Steve did a great job. A good shop gives a good reference. Would be happy to do business with you in the future.

[FASTEDDIE Z]

Youll love the new gears ! I just went from 273's to 373's . Big improvement :mrgreen:

[MonmouthCtyAntz]

Yea I went from 273's to 373's in my old 97z...nice improvement.

[Wolfblitz]

U have an adress on the shop? I've been kickin around changing the gears in my 99 Firebird but wasnt sure if it was worth it. But if your really happy and can notice a difference, i might as well see what its all about.

[Mike]

U have an adress on the shop? I've been kickin around changing the gears in my 99 Firebird but wasnt sure if it was worth it. But if your really happy and can notice a difference, i might as well see what its all about.

within the price range, gears and a posi will give you the biggest "seat of the pants" difference out there. any of the shops over on the right will do you right. ----------------------------------------------------------------->

if you want to use the shop mark did, take it to pm's

[Mark42]

Finally got around to changing the gear lube after the break in period. Said to change it after 500 miles, but I went about 2000 because its been just too darn cold to work on the car for the last couple of months!

I was really surprised how dirty/dark the lube was. It was filled with Mobile 1 synthetic 70-90 which is pale yellow and transparent. It came out grey and cloudy. There was also a layer of metal powder covering the magnet. Mixed with gear lube its like thick grey paste. Didn't expect to find that much after break in, but maybe the all gear Eaton Truetrac contributed to that. Also inspected the ring gear teeth for the wear pattern, and it looks great!

Here is a shot of the gears and Eaton Truetrac:

http://img.photobucket.com/albums/v437/mark42/1998%20Firebird/HPIM6519.jpg

Also added a drain plug, painted the cover, closed it up with a fresh Felpro gasket then filled with Mobile 1 again.

http://img.photobucket.com/albums/v437/mark42/1998%20Firebird/HPIM6525.jpg[/QUOTE]

Took it for a test drive and after half an hour there are no leaks.

[Zero4488]

All of that metal is from the break in of the gears...

[Mark42]

All of that metal is from the break in of the gears...

Yeah, I was just surprised at how much! I expected some, but as much as I found.

[Slow-V6]

I had a Eaton Tru track in my V6. This rear end with this diff was very loud all the time.That thing cost about 500.00 and lasted about a yr. Had it in my car for about 4 months then I sold my entire rear end to my buddy who had a 88 Formula and it lasted in his car about 6 months before breaking. He autocrossed his car. Its too bad they dont have the SLP Take offs still for 100.00!

After breaking 3 10 bolt rear ends in my V6 car and 1 so far in my 02 WS6 I have come to the conclusion that no matter what you do to your 10 bolt or no matter how much power you make if you race your car the 10 bolt will break!! I had Moser axles with a Eaton posi, T/A cover, and new everything and it still broke!! Cost about 1200.00 in parts to build that rear end.

[Mark42]

I had a Eaton Tru track in my V6. This rear end with this diff was very loud all the time.That thing cost about 500.00 and lasted about a yr. Had it in my car for about 4 months then I sold my entire rear end to my buddy who had a 88 Formula and it lasted in his car about 6 months before breaking. He autocrossed his car. Its too bad they dont have the SLP Take offs still for 100.00!

After breaking 3 10 bolt rear ends in my V6 car and 1 so far in my 02 WS6 I have come to the conclusion that no matter what you do to your 10 bolt or no matter how much power you make if you race your car the 10 bolt will break!! I had Moser axles with a Eaton posi, T/A cover, and new everything and it still broke!! Cost about 1200.00 in parts to build that rear end.

Wow! Talk about bad luck. Maybe you should talk to some rear experts. They typically put 500 hp into the Eaton with no problems. Something must be wrong for you to have these problems with such low hp. Most problems with rear ends are not the parts, they are problems with the installers. Spend the time to find the source of your problems, usually a new/better shop will be the solution and save you $$$.

BTW, the Eaton is silent. So any noise you have is with a bad gear setup. Again, that is an installer issue. Find a better shop.

And the SLP take off rears are about 50% weaker than than the Eaton. Please review your info and post a revised assessment with more detail. Thanks!

[Mike]

Wow! Talk about bad luck. Maybe you should talk to some rear experts. They typically put 500 hp into the Eaton with no problems. Something must be wrong for you to have these problems with such low hp. Most problems with rear ends are not the parts, they are problems with the installers. Spend the time to find the source of your problems, usually a new/better shop will be the solution and save you $$$.

BTW, the Eaton is silent. So any noise you have is with a bad gear setup. Again, that is an installer issue. Find a better shop.

And the SLP take off rears are about 50% weaker than than the Eaton. Please review your info and post a revised assessment with more detail. Thanks!

where do you get off with such a high and mighty attitude, telling him to reread his post and fix his info, yet you posted "with such low hp" when he never once mentioned his hp levels....

you mention it must be bad luck, but HUNDREDS of fbody owners have had the same issues with 10 bolts....

[Slow-V6]

Wow! Talk about bad luck. Maybe you should talk to some rear experts. They typically put 500 hp into the Eaton with no problems. Something must be wrong for you to have these problems with such low hp. Most problems with rear ends are not the parts, they are problems with the installers. Spend the time to find the source of your problems, usually a new/better shop will be the solution and save you $$$.

BTW, the Eaton is silent. So any noise you have is with a bad gear setup. Again, that is an installer issue. Find a better shop.

And the SLP take off rears are about 50% weaker than than the Eaton. Please review your info and post a revised assessment with more detail. Thanks!



Dude I dont know where you have been hiding for the past 20 years but the 10 bolt Rear ends are junk!! If you are making over 200hp and run your car at the track then it is just a matter of time. I broke a Stock 3.23 gear rear end with my V6 on motor!! My car put out 186 rwhp on motor at the time. Setup has alot to do with it but also how you drive your car. My Built rear end saw a couple of nitrous dumps at 5grand with some DR's. My car was putting 430 tq through the rear.

The rear end I broke on my WS6 was the bone stock 3.42 rear end. My car made 325rwhp at the time and I broke it cutting a 2.1 60' at the track on street tires!! Not even DR's.

In my V6 I had a 3.23 rear that was bone stock that broke at the track, I had a 3.73 ZT LS1 rear end that broke on the street, and my Eaton 4.10 rear that didnt break on me but broke on my friends car at the autocross track and it was the Diff that broke. On my 02 T/A My bone stock 3.42 rear broke at the track. I dont care if I break a rear end or not anymore because I have a warrenty on my T/A. Cost me 100.00 to get a brand new rear from GM!!

The bottom line is 10 bolts are junk. I wasted over 2000.00 on moding and buying other 10 bolts in the past on my V6 Firebird that All I should have done was save up and get a 12 bolt and be done with it!! I was nieve ( spell check) and thought I could build a solid 10 bolt that would last. I think I saw a artical in GM High tech on a 10 bolt in a 3rd gen with the car making 500rwhp or something. I thought if he could do so could I. Thats the joys of being young.

If you plan on running your car at the track and make over 200hp then you should save up for a 12 bolt rear end. It will save lots of time and frustration in the future and in the long run be one of the best mods you can do to your car.



you mention it must be bad luck, but HUNDREDS of fbody owners have had the same issues with 10 bolts....

I think that number is probably more like 1,000's of 3rd and 4th gen F-body owners.

[B4C]

Yeah Mark42 you been hiding under a rock? I broke my 10 bolt almost completly striped the pinion people have broken them in practically stock cars...its not the parts it the design its weak...ever seen a stock 10 bolt housing and a moser 12 bolt next to each other the 10 bolt looks like a little toy. 7.5in 10 bolts are junk! It has nothing to do with the quallity of the parts in them, they just arent beefy enough to hold any power...I broke mine doing a burnout...didnt hook until 5th sounded awful...then I continued to beat on it then it went boom.
http://www.njfboa.org/forums/showthread.php?t=48725

[Mark42]

where do you get off with such a high and mighty attitude, telling him to reread his post and fix his info, yet you posted "with such low hp" when he never once mentioned his hp levels....

you mention it must be bad luck, but HUNDREDS of fbody owners have had the same issues with 10 bolts....

He said it was a V6, I assumed it was stock. My bad. I'm not saying the rear is strong. I said the EATON is stronger than the OEM differential. Ring and pinions still break, but the Truetrac doesn't break as easy as the OEM differential.

I didn't tell him to "fix his info" I said... "Please review your info and post a revised assessment with more detail. Thanks! " which is a completely different request altogether.

Dude I dont know where you have been hiding for the past 20 years but the 10 bolt Rear ends are junk!! If you are making over 200hp and run your car at the track then it is just a matter of time. I broke a Stock 3.23 gear rear end with my V6 on motor!! My car put out 186 rwhp on motor at the time. Setup has alot to do with it but also how you drive your car. My Built rear end saw a couple of nitrous dumps at 5grand with some DR's. My car was putting 430 tq through the rear.

The rear end I broke on my WS6 was the bone stock 3.42 rear end. My car made 325rwhp at the time and I broke it cutting a 2.1 60' at the track on street tires!! Not even DR's.

In my V6 I had a 3.23 rear that was bone stock that broke at the track, I had a 3.73 ZT LS1 rear end that broke on the street, and my Eaton 4.10 rear that didnt break on me but broke on my friends car at the autocross track and it was the Diff that broke. On my 02 T/A My bone stock 3.42 rear broke at the track. I dont care if I break a rear end or not anymore because I have a warrenty on my T/A. Cost me 100.00 to get a brand new rear from GM!!

The bottom line is 10 bolts are junk. I wasted over 2000.00 on moding and buying other 10 bolts in the past on my V6 Firebird that All I should have done was save up and get a 12 bolt and be done with it!! I was nieve ( spell check) and thought I could build a solid 10 bolt that would last. I think I saw a artical in GM High tech on a 10 bolt in a 3rd gen with the car making 500rwhp or something. I thought if he could do so could I. Thats the joys of being young.

If you plan on running your car at the track and make over 200hp then you should save up for a 12 bolt rear end. It will save lots of time and frustration in the future and in the long run be one of the best mods you can do to your car.



I think that number is probably more like 1,000's of 3rd and 4th gen F-body owners.

Yep, I never said the rear was strong, just that the Eaton was stronger than stock.

Yeah Mark42 you been hiding under a rock? I broke my 10 bolt almost completly striped the pinion people have broken them in practically stock cars...its not the parts it the design its weak...ever seen a stock 10 bolt housing and a moser 12 bolt next to each other the 10 bolt looks like a little toy. 7.5in 10 bolts are junk! It has nothing to do with the quallity of the parts in them, they just arent beefy enough to hold any power...I broke mine doing a burnout...didnt hook until 5th sounded awful...then I continued to beat on it then it went boom.
http://www.njfboa.org/forums/showthread.php?t=48725

Yep, I never said the rear was strong, just that the Eaton was stronger than stock.

[V]

a big issue with the 7.5 10 bolts is the flex of the axle tubes as well, an issue where the strength of the carrier doesnt matter.

i broke my first 10 bolt with a stock setup while driving 5mph through a parking lot, part of the carrier came out through the rear cover.

the 10 bolt will live a long life in your car, but not the average f body.

[B4C]

Put your eaton rear in an ls1 car, wolnt last long if you don't baby it. How did you not say fix your info?? You said review your statement and Post a revised reassesment of your info....douche way of saying fix you info and get back to me.

[Blacdout96]

a big issue with the 7.5 10 bolts is the flex of the axle tubes as well, an issue where the strength of the carrier doesnt matter.

i broke my first 10 bolt with a stock setup while driving 5mph through a parking lot, part of the carrier came out through the rear cover.

the 10 bolt will live a long life in your car, but not the average f body.

besides welding the tubes, could gussets help strengthen the tubes in any way, or would it be a waste of time?

[Slow-V6]

I am sorry if I came off as trying to start ****. I am just posting up what has happened to me in the past. It doesnt really matter at all if the Eaton unit is stronger then the Stock ZT diff, If the gears break it will more then likely damage the diff like it did in my 1st rear end in my 98 V6. If the Axle bearings break it will more then likely damage the diff like it did in my 1st rear end in my 02 T/A. What I am getting at is that it doesnt really matter how strong a Diff is, the problem is with the size of the ring and pinion and how small everything else is.

When I was building up my V6 I had a great performance shop owner tell me he would install whatever I wanted him to install on my car but he always told me that if I was going to take my car to the track that I should get a 12 bolt rear end. I didnt listen to him and my car was down alot due to rear ends breaking. I was youger at the time and wanted to prove people wrong and didnt take advise on anything really. I wasted so much money on my car that if I would have done it right from the start I probably would have had a mid 11 second V6 F-body.

[Slow-V6]

Wow! They typically put 500 hp into the Eaton with no problems.


And the SLP take off rears are about 50% weaker than than the Eaton. Please review your info and post a revised assessment with more detail. Thanks!

I would love to see how many 500 rwhp F-bodies with a 10 bolt are out there..

I never said anything about how strong a SLP diff is what I was trying to say was if you just wanted to have a LSD diff that the Take offs were the best option for most V6 cars!! Hell I use to buy 10 bolts with stock LSD's and 3.42 gears for 100.00! people just give them away!!

[Slow-V6]

besides welding the tubes, could gussets help strengthen the tubes in any way, or would it be a waste of time?

Pretty much everything is a waste of time for a 10bolt. For you I would deff get a 12 bolt. You plan on modding the heck out of your car so a 12 bolt would be a good option for you..

[Blacdout96]

Oh I know that, jsut looking to extend the meltdown time, and to kill some time :lol: I'm takign one of my old rears I had laying around, and am dropping a used Torsen T2 in it with 3:73 gears in it. I'm not looking to make it bullet proof, 10 bolts were damned when they first left the factory.

[Slow-V6]

Oh I know that, jsut looking to extend the meltdown time, and to kill some time :lol:

Well in that case Go for it. cant hurt!

[Blacdout96]

yeah I got three rears sitting around here, time to do some detruction!!

[V]

besides welding the tubes, could gussets help strengthen the tubes in any way, or would it be a waste of time?

this is also in interesting idea...
http://www.lpwracing.com/p_axletubebrace.asp

i may try to extend the life on my 10 bolt, considering now i have 2 4th gens in need of strong rears and ill only cough up the cash for one right now.

[BonzoHansen]

a good rear cover that helps keep the dif in place and reduce housing deflection is helpful.

[deadtrend1]

a good rear cover that helps keep the dif in place and reduce housing deflection is helpful.

and the main cap stud kit helps too. But really, its all just a bandaid.

[NastyEllEssWon]

go to ls1tech and search 10 bolt rear. you'll see plenty of carnage from v6 to v8 to big boost turbo motors. the 10 bolt rear isnt even worth modding anymore with all the different rear options they have out there. swapping out the 10 bolt is the first mod anyone should do if building a fbody. even before touching the exhaust.

[MonmouthCtyAntz]

swapping out the 10 bolt is the first mod anyone should do if building a fbody. even before touching the exhaust.

I wouldnt go that far...theres plently of guys out there running heads/cam setups w/ no problems w/ the stock 10 bolt..

[Frosty]

To sum up 3rdgen/4thgen 10-bolts: No matter how much you polish a turd, it's still a turd.

Sure, people have put power through them and have been lucky...doesn't mean they're durable. I've had the 2 10bolts I've owned last...one had no power(86 LB) and my '00 Z28...never ran anything stickier than street tires.

The rear is junk, plain and simple. Some people have had luck with them but when a stock V6 on street tires can break them there's something wrong.

I'll stick with my 3rdgen 9-bolt until it breaks, then it's 12-bolt time.

[Slow-V6]

swapping out the 10 bolt is the first mod anyone should do if building a fbody. even before touching the exhaust.

If you plan on running your car at the track. If you just want to have a street car then a 10 bolt will hold up for a little bit. But the 1st time you go to the track you better have your AAA membership on hand.

[Slow-V6]

The rear is junk, plain and simple. Some people have had luck with them but when a stock V6 on street tires can break them there's something wrong.

My V6 had headers, full exhaust, and lid when I broke my first Rear. My car was making 186rwhp and 215rwtq!!

[LTb1ow]

My V6 had headers, full exhaust, and lid when I broke my first Rear. My car was making 186rwhp and 215rwtq!!

Annnnd my heads/cam slowmobile has yet to break my ten bolt. Luck of teh draw I suppose.

[Slow-V6]

Annnnd my heads/cam slowmobile has yet to break my ten bolt. Luck of teh draw I suppose.

I would go knock on some wood after saying that!!

[NastyEllEssWon]

the a4 doesnt put as much violent force on the rear as the manuals do. honestly if you plan to mod your car, youre probably going to be doing at least a little bit of spirited driving....and whats spirited driving without a few low end blasts :lol:



honestly if youre going to mod a car i stand firm in belief that you weed out any weak parts before you go adding any power. build from the rear forwards.

[Blacdout96]

I'm suprise there isnt any alternative GM rear options, like using an 8.5 rear form a second gen/large truck, or a 10.5 from a suburban or something.

[MyFirstZ]

i know its just a matter of time til my ten bolt goes. I know that i will not be repairing it either. Moving right on up to the 12

[B4C]

i know its just a matter of time til my ten bolt goes. I know that i will not be repairing it either. Moving right on up to the 12

Im pretty shure I broke my 12 bolt...what kind of numbers are you putting down.

[Tru2Chevy]

I'm suprise there isnt any alternative GM rear options, like using an 8.5 rear form a second gen/large truck, or a 10.5 from a suburban or something.

As stated before, the torque arm mount is the limiting factor. It's relatively easy to change shock mounts and spring perches on an axle, but the torque arm mount is cast into the housing, and adding one to a rear that doesn't have one is no simple task.

- Justin

[WildBillyT]

As stated before, the torque arm mount is the limiting factor. It's relatively easy to change shock mounts and spring perches on an axle, but the torque arm mount is cast into the housing, and adding one to a rear that doesn't have one is no simple task.

- Justin

Plus you get into width issues.

[NastyEllEssWon]

after being around and seeing all the 12 bolts that people have trashed and looking under the rear of some serious machines at the track and various car shows ive come to believe that when buying a rear and spending that type of cash on a rear you might as well spend the few extra and get the 9'' instead of the 12 bolt...theres also a dana rear thats supposed to be just as strong, maybe stronger....i think its the s60 but i dont have anything to offer on it beings im not familiar with it.....theres a guy on here that has one in his vert lt1...i think his name is blackbird something

[WildBillyT]

after being around and seeing all the 12 bolts that people have trashed and looking under the rear of some serious machines at the track and various car shows ive come to believe that when buying a rear and spending that type of cash on a rear you might as well spend the few extra and get the 9'' instead of the 12 bolt...theres also a dana rear thats supposed to be just as strong, maybe stronger....i think its the s60 but i dont have anything to offer on it beings im not familiar with it.....theres a guy on here that has one in his vert lt1...i think his name is blackbird something

You can break any of the rears if the situation arises. Josh broke two 9" rears.

Blackbird has an S60, as does Featherburner.

[Slow-V6]

But they all will last longer then a 10 bolt!!

[BonzoHansen]

As stated before, the torque arm mount is the limiting factor. It's relatively easy to change shock mounts and spring perches on an axle, but the torque arm mount is cast into the housing, and adding one to a rear that doesn't have one is no simple task.

- Justin

Plus you get into width issues.

All of which you can get around, but it would be cheaper just to buy the right rear that is made to fit.

[sweetbmxrider]

fab 9 is another option :)

[BonzoHansen]

A 9" by another name.

[sweetbmxrider]

plus steroids. they ain't no joke and can take some rpm from a standstill.

[JSPERFORMANCE]

Fab 9 is just a housing fabricated from plate steel instead of two stamped housings welded together. It still uses the same ol 9" center chunk which is what breaks usually. Nothing is "bullet proof" but any of the aftermarket rears will be sufficient for the abuse 99% of owners can throw at them.

[Mark42]

Ok, here is the fix for the noisy Summit Racing gears:




Get a magnaflow cat back system. It will drown out any other sounds.

[Slow-V6]

Ok, here is the fix for the noisy Summit Racing gears:




Get a magnaflow cat back system. It will drown out any other sounds.


Motive Gears are the quitest gears I have used. I had Richmond and they were loud.