Hey all - I need some advice on a 1996 Tahoe (last 8 vin TJ327978). I bought in used with 212k to pull our popup trailer. It's 4WD and I've discovered that the gear ratio in back is not what it should be. The Speedometer is way off (registers about 60mph while moving 50mph) and the rear tires squeal (drag) in 4WD on pavement. (REALLY wish i'd tested on pavement b4 buying, but it's mine now.) I haven't had anyone look at it yet, but I'm pretty sure that someone replaced the rearend with one that doesn't match the front and there are yellow grease pencil marks that look suspiciously like they were made in a wrecking yard. Specs say the rearend should be 3.42 for this vin. Assuming I want to fix this, what should I do here? I'd like to get away as cheaply as I can, given that I don't plan to drive it daily. does it make more sense to have someone rebuild the rearend with gears that match the front? or shoud I be looking for a replacement rearend? if raplacement is the best option, how do verify the ratio of a rearend before I buy it? FYI - I'm in Phoenix, AZ and there are a few parts yards around, so I think I'll have a few to choose from.

Thanks for whatever input you can give.

 

i'd pull the diff cover and start counting... ring / pinion is gear ratio...

if the rears are dragging it means the front are pulling faster and have a higher (numerically lower) ratio than the rear does.

Unless you really plan on using 4WD, I'd leave it as is... obvously something will eventually break unless both axles are the same ratio... how often do you use 4wd?

I'd check what the rear is, sounds like they geared it down for towing, if you town i would match the front to the rear, if you don't tow, I'd re-gear the back.

Since you live in AZ, I doubt you see snow every winter like me in PA... so really you could just live without 4x4.

Gearing 'up' to a smaller : 1 ratio would give you more MPG, but not enough to off set the cost of gears + job...

With jeeps we do this stuff all the time.... I have 4.11s factory to run 35s, but wouldn't mind some 4.88s...


This site has a ton of good info:

http://www.carbibles.com/transmission_bible.html

like you said you could swap the whole axle vs just the diff; I know on wranglers the gear ratio is stamped on a plate on the diff cover, a small .5" x 4" strip... I think it is on GM as well... both use Dana axles I belive...

 

Thanks - I'll pull the cover and count em up... I haven't done that before tho - I assume the differential is full of oil?? grease?? M&Ms??

It is something I need to fix or get a new puller. Actually plenty of snow and ice in Flagstaff and Showlow AZ, but we also take trips to Oregon.

 

if there was m&ms in my diff i would have already ate em all BUT anyway what u will need is a socket and rachet( i dunno how big the bolts are) and a flathead screwdriver(to pry off the cover) and something for the fluid to drain in, to put it back on u will need 2 bottles of diff fluid and some gasket maker( any will work)

 

Thanks Davey - much appreciate it.

 

no prob.

 

when you do take it off leave the top half of the bolts in but loosen them a little then pry the bottom open. So that way the fuild will not end up everywhere

 

forgot to mention that..good catch

 

DONT get it on your clothes it smells horrible

 

thats no fun though