Most likely donor truck with either 3.08 or 3.42 gears

[gun4hire]

I know there is an axle section for the lifted and offroad guys, but didn't see one for the street truck group so here I am.

Current build:
1989 Chevy Cheyenne 1500 work truck. 5.7L, nv3500 manual trans and what I believe is a 3.73 rear axle.

My issue is that I do a lot of highway driving at 80mph+. When I got the truck, this wasn't too bad because the PO had 31" tires on it. However, after going to a 26" tall street tire, the engine is revved out most of the time. Also, 1st gear is practically useless from a red light because you clutch to shift into 2nd before you've even cleared the intersection. Even little cars just pull away easily while I'm not under power because of the early shifting.

I'm prepping for a 6.0 LS swap and retaining the NV3500, but what I'd like to do is simply score an inexpensive rear axle out of another OBS with numerically lower gears. However, whenever someone is parting out a truck they never know the gear ratio and the tag is often already gone (just like mine is missing). They always offer for me to come out to look for myself, but I'd rather not drive all over unless I'm somewhat certain they will have an axle I want.

Is there anything I can look for or ask that might narrow this down beforehand and save me a few trips? I'm just looking for an inexpensive solution for now knowing the LS will have plenty of torque for the gears and also knowing that in the future I may need to step up to something stronger.

 

[scott2093]

They should be able to provide a vin#
then you could maybe look on parts site like GMpartsgiant..search by vin....... do they show the gears there?hmm...anyway...vin will get you more info for sure....
could use compnine....assuming the gears haven't been switched over at some point obviously

car-part.com is usually pretty much right on with their searches...have you tried there??

 

[gun4hire]

I've never tried using the VIN - I didn't know the VIN would provide an axle code. I'll have to check that out - thanks!

As far as the sellers, I'm goin cheap and local folk that are parting out a truck rather than parts yards (local or national)

 

[L31MaxExpress]

Biggest flaw with the NV3500 is the gear spacing. It works for getting an underpowered 4.3L towing a trailer rolling but not much use beyond that.

 

[gun4hire]

3rd and 4th gear on surface streets are a blast. 1st gear is just too low and that's with a stock 350. With the 31's on there, it wasn't nearly as useless so I'm hoping to replicate that with the numerically lower gears. The LS should provide plenty of torque the 350 doesn't have to compensate.

 

[someotherguy]

I think 3.08's in a GMT400 are pretty rare. I've seen them in person one time - and that was on a '91 C1500 extended cab with 5.7/NV3500. RPO code is GU4 in the event you find any with the SPID label still legible in the glovebox. Like Scott mentioned, assuming the gears haven't been changed out already. Also, assuming the entire rear end hasn't been swapped out already, as by this time, many 8.5" 10 bolts in these trucks have failed and been boneyard swaps. These were hot items at my salvage yard.

GU6 of course would be 3.42's ("standard ratio") and can be found in many C1500's. IMO the most common axle ratio for your typical C1500. 3.73's were rare by comparison, when you're talking half ton 2WD. Mind you most of the trucks I've owned/worked on have been V8's, so I can't speak for the V6 trucks and what was common in those.

Richard