Topic: Are all 4.88 3rds really the same exact ratio?

[ShawnF]

Hello,

It took me a while to save up, but I finally got ahold of a couple 4.88 3rds for my '85 pickup.  I installed a factory V6 third in the rear.  I couldn't find another V6 third, but I found a 4 cylinder 3rd with aftermarket gears in it.  My transfer case USED TO shift really nice into and out of 4wd from 2wd, moving or sitting still.  Now, it only shifts into 4wd smoothly.  And it just doesn't seem to behave the same as it used to with the stock 4.10's.  There seems to be some mild wander (though it could just be frost heaves in the road).  Now, to shift out of 4wd I typicaly have to accelerate fairly hard, let off the gas and shift into 2wd at the same time.  Even then, it takes a bit of force and the truck suddenly breathes a sigh of relief.  Yes, I'm sure both 3rds are 4.88's.  I counted the teeth on both of them and they were both right for 4.88 and matched each other.  I believe the aftermarket gears even had 4.88 stamped on them. 

Anyway, has anyone ever experienced issues running a V6 factory 4.88 3rd with a 4 cyl. 3rd running aftermarket gears? 

[seanc]

for a while i had 4:38 and 4:56 shifting sucked most times. have you verified the ratio's?

[ShawnF [OP]]

Yup.  Both rings had the same # of teeth along with the pinion gears.  The aftermarket gears had the ratio stamped on them.

I had another pickup that had a 4.88 in the rear and a 4.10 up front.  That was VERY obvious on glare ice that the ratios were different.  The truck didn't want to move and hopped when it did.  I had to move that truck once during the winter time about 100ft and forgot the 3rds didn't match.  I never went faster than 1st gear.  The truck also did not want to steer right.  I would think there would still be an obvious difference if I had something like a 4.56 and a 4.88 at the same time.  I counted and recounted the teeth on both 3rds to make absolutely sure they were the same. 

[Marlin]

No problem, 4 cyl diff in front, and V6 diff in rear.
As long as it is the same ratio, it will work just fine.

[79coyotefrg]

make sure your tires are NOT the same pressure front and rear,   if they are your rears will be slightly taller because of the weight difference front to rear,  try 35psi front and 28psi rear

[ShawnF [OP]]

Good point.  I should probably check my tire pressure.  I am running an aftermarket fiberglass bed and have 3 sand bags in the back (minnesota winters are fun). 

Whatever is causing the problem it has to be something small.  I'm definately running 4.88's front and rear.  I used non-synthetic basic bearing grease for the birfs and wheel bearings when I put everything back together. The grease wouldn't somehow be causing drag, would it?  I filled the housings about 3/4 full of grease.  Then again, I would think the grease would warm up enough for that not to matter.