NEED HELP! Center dif lock/ 4.88 regear question! (1 Viewer)

[Ragnaroek]

Yes.

I’m just not understanding how a full time 4WD system that pushes power to both axles could operate effectively at highway speeds and daily driving conditions with two different gear ratios.

Maybe I’m missing something. Hoping to get clarity before I go tearing things apart.

I was crossing my fingers that people would hop on and say some slipping/ driveline binding was totally normal and to carry on

The center diff doesn't know and doesn't care If you're driving a straight line or not. If one axle ist easier to spin than the other, more power will be going that way until the demand equalizes. Try to see it like a normal diff with your front/rear axles at the ends instead of two wheels. Even if your diff ratios are messed up between the axles, it would just work normaly. Just like a diff in an axle with two mismatched wheels would do.

If you lock it, you'll get a fixed 50/50 distribution of power and RPM front and rear, like in an old school 4WD system.

 

[jordancollard97]

Update.
I took it out in mud/ grass.

It absolutely only binds when the center dif lock is engaged.
Tried it in 4 high and 4 low. No difference.

Without center dif lock engaged- totally smooth. With center dif lock, binding/ hopping/ sliding.

Time to check the rear axle to see if it’s been geared to 4.88s? I know for a fact the front has. I assumed the rear had.

Or more likely and issue with transfer case?

 

[leonard_nemoy]

Your on the right track. Put the axles in the air and spin a tire 1 rotation and count how many times the driveshaft turns per 1 tire rotation. Do this for the front and rear and hope they are the same.

 

[RoaringFork]

Update.
I took it out in mud/ grass.

It absolutely only binds when the center dif lock is engaged.
Tried it in 4 high and 4 low. No difference.

Without center dif lock engaged- totally smooth. With center dif lock, binding/ hopping/ sliding.

Time to check the rear axle to see if it’s been geared to 4.88s? I know for a fact the front has. I assumed the rear had.

Or more likely and issue with transfer case?

Have you checked to ensure all the tires are the same size?

You could remove one drive shaft, lock the center diff and drive. If no binding, then re-install shaft and remove other shaft. If still no binding, I doubt it would be the tcase.

 

[BuzzAZ]

See- I’m getting this answer from half of the people.
And another from the other half.

There’s plenty of information on this board for you determine the right answer. Let me ask this: do you think Toyota built in the locking feature just to keep the wheels locked when turning? How do you suppose the center diff can differentiate between disproportionate force caused by turning and disproportionate force caused by a lack of traction, binding in the diff, etc?

 

[jordancollard97]

For anyone interested:

Confirmed- 4.11s in the rear, 4.88s in front.

Binding was due to mismatched ratios.
Rears getting regeared.
Now time to pray no damage to TC was done.

 

[BuzzAZ]

How many miles since the front gears were done?

 

[jordancollard97]

How many miles since the front gears were done?

Truthfully not sure. PO did it- but almost positive under 5k.
Did not drive far while binding.

 

[jordancollard97]

Truthfully not sure. PO did it- but almost positive under 5k.
Did not drive far while binding.

Like I said, it would only bind with center dif locked.

 

[MMaxim]

For anyone interested:

Confirmed- 4.11s in the rear, 4.88s in front.

Binding was due to mismatched ratios.
Rears getting regeared.
Now time to pray no damage to TC was done.

That was the only logical explanation.

 

[BuzzAZ]

You may have only noticed it when it was locked, but the problem was there the whole time. You may as well have had 30” tires on the front and 35” tires on the back.

 

[jordancollard97]

View attachment 3448434View attachment 3448435View attachment 3448436You may have only noticed it when it was locked, but the problem was there the whole time. You may as well have had 30” tires on the front and 35” tires on the back.

Any suggestions on how to proceed with addressing this after I regear the rear dif??
Is there a way to test if I’ve shot my viscous coupler? Or if my transfer case is toast?

Not sure how to Troubleshoot this especially if it seems to still be running fine.

 

[BuckarooBanzai]

This is something I’ve never seen before. What was the PO thinking about when regearing one axle only??? We may never know, but it’s going to bother me forever.

I’m glad you figured out the issue. Keep us updated on the progress.

 

[77mustard40]

Was there a VC in a 94 or did they start in 95?

 

[BuzzAZ]

My understanding is that disc braked, ABS equipped models have VCs. His pic shows stock aluminum wheels, so I assumed his had it, but something to confirm. I also thought 3x locked came on the FF/disc/ABS only but that may not be the case.

 

[tmxmotorsports]

My 94 triple locked has v/c abs ff rear disk brakes

 

[BuzzAZ]

Any suggestions on how to proceed with addressing this after I regear the rear dif??
Is there a way to test if I’ve shot my viscous coupler? Or if my transfer case is toast?

Not sure how to Troubleshoot this especially if it seems to still be running fine.

I’m not aware of an easy way to tell. I’d search around - I’m sure someone smarter than me has posted a way to test function. If it’s running fine then I guess up to you if you want to deal with it or not. It can be replaced separately but still expensive. I’m sure there’s many that don’t work well (or at all) anymore and it goes unnoticed. Unless you’re in icy/wet/low traction conditions regularly you probably won’t notice a difference. It’s like driving with an open diff versus a limited slip diff. You still have the option to lock it like a “normal” transfer case.

More importantly, I think I would pay a shop that’s familiar with 80’s to go through it in depth. This is a pretty egregious error on the PO’s part. I would be seriously concerned about other “upgrades” hiding in the truck.

 

[tmxmotorsports]

I will say this is something that usually doesn't happen something must have happened obviously prior to op maybe po was lifted bigger tires and lowered it and put stock gears in the rear dick move but no telling what happened

 

[bj70bc]

wow, just wow