Backlash in the Transaxle?

[maddog]

ok

did u just lift one front tire at a time and spin the one that was lifted or lift both and spin?

because if u lift both u have to have a friend hold one tire while u try to spin the other

also when u tried to spin the rear tires was the parking brake off?

[DoctorDex]

Yes, I made sure the parking brake was off.

When I lifted one front tire @ a time, both the driver side & passenger side front wheels spun easily.

When I lifted both front tires, I had a friend turn the driver side wheel forwards and I turned the passenger wheel forwards. There was a small amount of resistance and if I let go of the wheel while the other person was turning it, it would turn backwards.

The amount of resistance felt for the front wheels was much less than the rear. If I was to spin the front wheel fairly quick and then stop, it would continue spinning for at least half a turn. When I tried this with the rear wheels, the wheel would stop spinning as soon as I let go.

Does this mean my front VCU is bad?

Declan

[maddog]

well the problem with testing from the rear is that your also getting resistance from the rear lsd and the t-case

u said when u lifted both front wheels u and ur friend both turned the front wheels together. try having him hold the one so it doesnt turn at all and then turn just yours. let us know if it still spins as easily

if so it would seem to be a bad center vcu

you dont have a front vcu

[DoctorDex]

It doesn't spin as easily as the rear wheels, but there is some resistance. If I get the wheel spinning and then stop pushing it, it'll turn about 1/4 - 1/2 turn before it stops.

[DoctorDex]

So, I should just replace my center diff. VCU?

Does anyone know what the lifespan is of an average VCU? I know it all depends on driving habits, towing etc., but how old would a VCU have to be for it not to be considered worth buying?

Is there any way to test a VCU while it is off the car?

Declam

[maddog]

as long as there is resistance it should be ok

see the issue with these tests is your also feeling resistance from gears, bearings, etc

with the vcu out of the car i beleive im the only one to actually take torque ratings

on a brand new one it took 70 ft/lbs to turn the vcu
on one with 140k on it the torque was 20 ft lbs
a bad one is measured in inch lbs so you should be able to tell fairly easy with it out of the car

the one with 140k was mine and i still raced without any problems but i may not have gotten any issues becasue of suspension setup

[Phil]

Originally Posted by maddog

In my expert opinion, it needs more cowbell.

Fixed for you, Dan.

[DoctorDex]

Maddog: What procedure/tools did you use to measure the torque values needed to turn the VCU?

I'm going to pull my VCU on Monday or Tuesday and I'd like to measure the torque rating before I run out and buy a new one. I'll keep you posted.

Declan

P.S. I like the quip about the cow bell.

[maddog]

i put the vcu in a vice and then found a socket that would fit over the driving teeth of the front pinion. then hooked up a torque wrench to the socket and put the front pinion in the vcu.


need less asshattery

[DoctorDex]

I finally pulled my output shaft & VCU. My output shaft looks good and it must have been changed by one of the previous owners. However, I can't say the same about my VCU.

I found a bunch of viscous goo in the VCU case and I put my VCU in a vice and it was could easily be turned by hand. I tested it with a torque wrench and the amount of torque needed to turn the VCU was in the inch pound range, which is very bad.

I also confirmed the theory that the excessive backlash I was experiencing was coming from the hammered out dowel pin holes. The amount of "play"/backlash between the planetary gear assembly and the VCU is roughly the same amount that I measured when I turned the output shaft (transfer case side) by hand.

I've ordered a new VCU, but I'm unsure as to whether or not I should replace the 18 spline output shaft now (while its still good) with the 300m ouput shaft. Now would be the time, but I'm not sure I can pull together the cash.

Declan