changing differential...
 

Can I change the center diff in a Dana 70 without having to re-lash the gear set?

basically the vehicle has an open rear with 3:55 gears.
I want to pull the open diff and swap in a posi unit, using the same 3:55 gears set.

Can i do that? or is it not recommended. I don't see why it wouldn't be OK, since the pinion gear isn't changing depth and the ring gear must spin centered on the new differential. As long as the posi is designed for that application, the ring gear mounting flange should be the same tolerance as stock so it should be in the same place...right? lol


Its a Dana 70 floating 8 lug rear.

One of the reasons shims and such exist is to make up for differences in production tolerances. IMO a diff is not a precision design. Chances are you will need to set it up again.

You can give it a shot and see how far it's out though. Maybe you will get lucky.

another option is swapping out the whole rear axle for a posi one, would cost around 500 or so. And then id have the original as a back up, since it only has 70k miles on it.

It seems a posi diff(aftermarket) cost at least 500.

Can i get a kit or something for the dana to covert the open to a posi?

or even something like this?
http://www.ebay.com/itm/DANA-70-80-3...-/110550564897

The lunchbox lockers like that one do make a little bit of noise when turning.

what type of car?

It doesn't really matter. But its most likely his dodge 2500 pickup

I'm not the expert in rear ends, but when we swapped out the posi for the spool, we reshim'ed it.

The lunchbox locker (the lock right you linked to) is a decent setup, but if you have never driven a truck with a locker before you might want to see if you can borrow one from a friend for an afternoon. Lockers, especially that style, act quite a bit differently than a posi.

- Justin

well that one i linked to says it unlocks when making turns. i know a regular locker wouldn't. I've driven a prostreet 69 camaro with a locker on the street. but maybe the 27" wide tires added to the nightmare of low speed turning. lol

and the 8 lug Dana 70 should have given it away that its a heavy duty truck.

noise isn't a concern, it would probably be covered up by the diesel engine/exhaust.

no, any locker should unlock while turning and such....some are just more noticeable about it than others. The lunchbox lockers are typically pretty loud, but as you said, you aren't driving a quiet vehicle either, so I doubt the noise itself would be noticeable.

- Justin

Yes. Anything that is a differential will allow one wheel to spin at a different speed that the other. Hence the name.

A spool is not a differential. A posi/LSD, locker, Wavetrac, Trutrac, etc are all diffs.

ah yes spool, that's what i drove in the '69 camaro. I posted this morning while still at national guard drill, i wasn't very rested so wasn't thinking clearly, haha.

now whats the difference in driving a locker like above vs. a regular posi?
I use the truck to go back and forth with landscaping stuff in the bed, and then to tow my car trailer. it goes out maybe once a week if that.

A posi/LSD allows for slippage, so you can have variations in the amount of power being applied to each rear wheel at all times. A locker is basically like a spool with a self regulated on/off switch (unless you get a selectable locker, but that's really for off road minded folk). When locked, the locker is like a spool, both wheels getting exactly the same amount of power, but when unlocked, it's just like a stock open diff. There is no in between with a standard locker.

I know James didn't DD his v6 'bird much, but I'm 99% sure he had a powertrax lunchbox locker in his 10 bolt. You can ask him how it drove on the street with that installed (or if you still have that rear you could slap it into one of the f bodies you have laying around and take it for a spin :lol: ).

- Justin