IFS front diff ADD vs. Non-ADD? (1 Viewer)

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Yup, my set cost me $100 and a set of 4 cylinder 4.10's... :D

Warning, tech....

There are 2 vac lines on my 94 ADD front diff, one locks and the other unlocks, it does not seem to need constant vacuum to stay locked, although I'm sure I'll just plumb it into the manifold vacuum so it's always trying to lock... :cheers:

Se my above post. Take the time to swap out the long tube and install a seal on the ADD unit. It keeps one wheel from turning the carrier constantly and allows you to use the needle bearing tube for longevity.

It's a good swap; no doubt..
 
what is the reason for getting rid of the ADD diff.? I know you can eliminate the vaccum system and plug off all the s***. I guess the goal was to simplify the system. But from a structural standpoint is the non-ADD diff. any stronger?
I think I saw the write up on MUD, guy took the diff cover off and moved the shift fork to the engaged position and capped the vaccum ports.
cheers
 
My truck was not factory add equipped from the factory (it has locking hubs) and the long axle tube was just a tube with a 1 piece axle shaft inside. I did not want to replace that simple reliable one piece axle with a two piece model that has a splined locking collar and a vacuum actuated mechanism incorporated into it. When I swapped in factory 4.88 diffs I chose not to use the add axle provided and kept the original axle since I had both complete units to work with and all day to swap parts.
 
I have to confess, I have never had a problem with my ADD diff., therefore I havent tore it apart yet. I guess I really only know about things that have gone wrong, because you have to fix them.

But I think I understand what you are saying. The non ADD diff has a different axle shaft on the long side. If it was my way I would not have ADD, but until a 4.56 non ADD diff comes up ill use it.

So it is a strength/complexity issue? However the short side axle is the same between the two different models?
 
sorry to bring up an old thread, but does anyone know the part # for the oil seal on a non-ADD diff housing? i'm in the middle of the tube swap and wanted to use a new oil seal if possible.
 
ADD was the show room floor device that was designed to make mama happy. Too bad it has a failure rate, cost loss of milage &
loss of performance. For those who have a faulty vacuum system and want to eliminate the ADD without having to tear the front-end apart, we make a block-off plate that holds the two axles in the locked-together position.
I think I read above that some think you can eliminate the ADD merely by replacing the tube for a non-ADD tube??? What am I missing?.
Regarding factory 4.56 and 4.88 gear ratios, an automatic tranny OR 31x10.50 (either one) got you a lower gear ratio (i.e. from 4.11 to 4.56). Both auto tranny and factory installed 31x10.50's got you 4.88 gears.
 
You're never going to find a 4.56 diff so it's an academic question, right? Seriously, just regear and get on with lighting up that set of cute dumbells you've scribed into your instrument cluster. :steer:

OK, I admit it. I have no idea.

They exist. Found on trucks with manual trannies and 31" tires from the factory. I have a rear on my 4Runner.
 
No, 4.56's are pretty common behind the V6/Auto, the problem is finding a set that someone will let me have..... :rolleyes:


Bzzzz, wrong answer. V6/auto, 31" tires had 4.88, even better. :p
 
I think I read above that some think you can eliminate the ADD merely by replacing the tube for a non-ADD tube??? What am I missing?.

Yep, remove 4 bolts, pull the ADD axle tube off and bolt on the non-ADD tube. Straight swap, did it several times already (to put an ADD diff in a non-ADD truck)
 
Figures there would be exceptions. I just remember when I bought mine that I was looking for a V6/auto in the boneyard.
 
Yep, remove 4 bolts, pull the ADD axle tube off and bolt on the non-ADD tube. Straight swap, did it several times already (to put an ADD diff in a non-ADD truck)
I believe you, what about axles?????
 
I believe you, what about axles?????

IIRC this applies up to '95 model year (maybe beyond?) - like I said, I've done this several time putting an ADD front diff into my non-ADD rigs, a pretty simple swap
-CVs and axles are exactly the same
-the non-ADD 1/2 shaft and tube slide right in and bolt down the same as the ADD stuff (use a bit of red RTV to seal the tube to the carrier)
-the passenger side ADD CV drive flange stays where it is
- the ADD diff carrier uses needle bearings to support the inner 1/2 shaft, the non-ADD uses a bushing, but the half shaft will fit in either way and I've always left the needle bearings in

ifsdiff2.jpg


the hubs on the spindle are obviously different - the ADD uses drive flanges on the hub that keeps the CVs spinning all the time (instead of manual disconnecting hubs)
 
Okee-Dokee, so you are replacing housing and axle. I just needed clearification that you in fact had to also change the axle, not just the housing.
 
yeah, the way I understand it the ADD axle is 2 pieces - just simpler to replace the whole thing
 
So after the non ADD system is in place. What do you do with the vaccuum lines, plug them? And jump the electrical sensor so the dash indicator still works?
 

Users who are viewing this thread

Back
Top Bottom