T4 Trans / Diff puzzle...

[Dogbone]

Im sure this has been seen before....

T4 trans, diff wasted by my lack of adj. and my mamba max. I jb welded it together, fine...but made it too "thick" ...I get that part. When cases are tightened it gets hard to turn. I took the diffs from 2 other T3s and a GT and tried them all, no good, still gets tight. But the T3s gear seems to be smaller...in diameter.

Well after some filing, I get the trans diff assembly to spin free when in my hand and also while mounted to chassis, but when I add the dogbones, it gets tighter, then when motor added its WAY too tight.

Hope I didnt confuse everyone, but maybe Im missing something very simple?

Thanks

[Asso_man!]

check the diff screw, it get sometimes slightly bent, just my 2 cents, difficult to tell from here

[Dogbone]

Well, after more insight into this it appears that my motor is the culprit... after I pulled the motor out, it rolls and feels pretty good...(yes I worked late on it last nite)

Ill try another motor & pinion

[Eau Rouge]

First problem is you should NEVER have JB Weld around any diff parts. Ever. A new thrust assembly and diff rebuild kit for a B/T4 Stealth assembly is $8. You pretty much just ruined any ability for the truck to ever turn again. A spooled rear will make for an awful handling truck—far worse than any tightness would ever have.

Second, the B2/B3/T2/T3 diff is a completely different differential and case. Don't mix and match the gears in them with your T4 tranny. They are not the same components and will not work together.

Second, how tight are you bolting the diff halves together to make tension on the moving parts inside? Some dirt oval guys will use motor shims (.010) to shim the diff halves apart for smoother and freer running, but the stock setup is fine for 99% of the population. Overtightening anything bolted to plastic will yield poor alignment and bad final results. My bet is that you ham-fisted the assembly the first time and ruined the diff case, which is why nothing else spins freely.

Your motor should have nothing to do with the tolerances of the diff and tranny case. If it is, you are only seeing the problem compounded by the mounting of the motor and the meshing of the pinion to spur—which I'm guessing is also too tight.



You might also think about downloading a PDF copy of the T4 manual if you haven't got one. They instructions will help you assemble the tranny perfectly and should be followed to a "T" if you want the truck to run properly.

[Dogbone]

First problem is you should NEVER have JB Weld around any diff parts. Ever. A new thrust assembly and diff rebuild kit for a B/T4 Stealth assembly is $8. You pretty much just ruined any ability for the truck to ever turn again. A spooled rear will make for an awful handling truck—far worse than any tightness would ever have.

Second, the B2/B3/T2/T3 diff is a completely different differential and case. Don't mix and match the gears in them with your T4 tranny. They are not the same components and will not work together.

Second, how tight are you bolting the diff halves together to make tension on the moving parts inside? Some dirt oval guys will use motor shims (.010) to shim the diff halves apart for smoother and freer running, but the stock setup is fine for 99% of the population. Overtightening anything bolted to plastic will yield poor alignment and bad final results. My bet is that you ham-fisted the assembly the first time and ruined the diff case, which is why nothing else spins freely.

Your motor should have nothing to do with the tolerances of the diff and tranny case. If it is, you are only seeing the problem compounded by the mounting of the motor and the meshing of the pinion to spur—which I'm guessing is also too tight.



You might also think about downloading a PDF copy of the T4 manual if you haven't got one. They instructions will help you assemble the tranny perfectly and should be followed to a "T" if you want the truck to run properly.

Thanks! I love the "ham-fisted" part...Im still laughing. I was sitting here with a broken diff at midnite and felt like attempting a locked diff, your right...it handles like crap. 8 dollars will definetly be leaving my pocket at the next LHS visit. But its a learning expirience. As was learning my first spur/pinion set up. I doubt I damaged anything when tightening the case...My Ingersol Rand 1/2" impact only cranks out 200 ft lbs...that shouldnt harm plastic, eh? The hardest part was using super glue and duct tape to get the allen wrench to stay on the gun....

Seriously, though, thanks for the input, the laughs and any help you intended to give. It is apreciatted.
Peace

[Eau Rouge]

If you are replacing the diff pieces that were previously epoxied together, you will probably need a new center gear, diff balls, and possibly out drives. A smooth diff should have NOTHING inside the diff or case—no dirt, no glue, no grease on the gear teeth—nothing. Anything else inside the case will make a mess once it starts running, and could potentially damage the diff.

A few tips when rebuilding the tranny...

- Pre compress the diff spring inside the outdrive (on the opposite side of the thrust washer). Use a pliers, and give it a few squeezes before installing it.

- Use only a fly fart of the Associated clear Stealth lube inside each hole of the diff center gear. No more—no less. Anything more than a sand spec of lube makes a mess and causes drag.

- Use ONLY Associated black grease inside the thrust assembly, and make sure the balls in the thrust plates are completely packed with the black grease. Wipe off any extra before assembly. Again, any extra lube will just make a mess and attract dirt and grit later, which wears everything out.

- Follow the instruction manual directions on tightening the diff properly. I mean EXACTLY. If you do it properly when you are building it, you'll never adjust it again. Too tight, and you'll have an ill-handling car, and too loose, and you'll burn it up and melt stuff. Remember, the diff is NOT a slipper clutch. If you need a slipper, there is one on the outside of the gearbox to play with.


That should get you a diff worth racing.

[carloco8]

- Use only a fly fart of the Associated clear Stealth lube inside each hole of the diff center gear.

Nice analogy but Doug is right. Use too much grease and it just flings off of the diff gear on the first run.