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Gearing question on a '91 blazer

S

smier

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Alright, I've had it with my stock 10 bolt rear in my '91 Blazer. Constant cover leaks, same broken cover bolt, leaky seals, bearings that go bad, and I've already spent too much money on it, and I'm starting to question if some of my problems aren't related to a bad housing, I believe the previous owner may have slid the truck into a curb or something because the rear wheel was bent badly... This is not a rock crawler or mud truck, the most wheeling it sees is the occasional snow storm, and I usually engage the 4 wheel drive once a month just to run it for a bit and keep things oiled up. I daily drive this thing 40 miles a day back and forth to work.

Now, I was almost ready to put a new ring and pinion and all new bearings in it, but I just have a bad feeling it's pointless. Enter a NOS 10 bolt gov bomb/loc with 3.08's complete drum to drum in the crate... Do I regear it? I think I currently have 3.73's, or do I rebuild my front and regear it to match? How would a 350tbi/700r4/np241 respond to 3.08's? I'm currently running stock suspension and 31's.

This is my cheapest option, I've been watching CL and other sites for used options, hard to find near me, worn out, or just too much $$$$. Plus I have to borrow a shop, and buying a parts truck is out of the question.
 
I think you`d need to recalibrate the electronic speedo if you swap ratios. You could also look for a 12 bolt from an earlier truck. You would be a little more doggy off the line w/3.08`s, but would lower RPMs onthe high end. The NOS doesn`t sound like a bad deal for a DD. Is anyone on here parting a rig around you?
 
You had mentioned somewhere of an upgrade to 33s too right? In which case you would want to regear to 4.10.

3.08s would kill your power and mileage even with stockish tires.

So, sounds like the problem is the rear axle housing being bad. If it were me, I'd live with the f'd up rear for now and find a good replacement to rebuild and regear. Ultimately, I'd be looking for a 6 lug 14b sf from an 88-98 to swap in. Yes you will have to get spring perches and shock mounts welded on but it will be worth it. I'd find one and rebuild and regear to 4.10. Then I'd buy the stuff to regear the front to 4.10 as well. Swap it all in when time and funds will allow. But that's what I'd do, may not work for you.
 
Just went from 3.08s to 4.10s with 32s and what a difference. Only thing that sucks about the swap is that my speedo was accurate before, seems the only thing the po got right :D
 
You gotta do what's best for your wallet.

If that is buying the NOS and regearing, then go that way. However, to keep it as cheap as possible, buy the NOS, pull the current axle and take the ring/pinion out, put them in the NOS, put the NOS under your truck and call it good.
 
Gunny65 said:
You gotta do what's best for your wallet.

If that is buying the NOS and regearing, then go that way. However, to keep it as cheap as possible, buy the NOS, pull the current axle and take the ring/pinion out, put them in the NOS, put the NOS under your truck and call it good.
Click to expand...


I was gonna suggest this too, whats wrong with your current r+p?
 
3.08 gears suck. 70's and 80's era effort to get more mileage out of them. Unless you were going to put 235/75R15's or 30's on.

I'd keep the 3.73's and 31's and just rock it like that. What faster speed you'll be spinning at road speeds will probably be made up for the truck not grunting to pull itself off from a stop.

Years ago I regeared a Ranger from 3.27's and 31's to 4.56's and 33's and the gas mileage went from 11-12ish to 14.5-15mpg immediately. Proper gearing helps a lot.

If the guy whacked the axle hard enough to bend it I'd wonder about the gears too. A bent axle housing can make a ring and pinion chew itself up. Easy enough to get a new set of gears.

Also, since you'll be regearing and it will all be apart, ditch the Grenade Lock factory junk and put in a posi/locker of your choice.
 
You guys have kind of confirmed my thoughts, I think I'll just regear the new rear before I swap it in. I'll still be ahead on cost, and for how I use this truck I might not have to worry about it for a long time. I think I'll take my chances on the gov loc, I'll upgrade if I ever get into using this thing hard. Right now it's my DD and family cruiser for fun, I've read of guys using these things in burnout competitions with no problems, and others exploding for no apparent reason... As far as reusing my gears, I need closure, this rear is like a bleeding wound. If I reused any of it, I don't think I'd be able to sleep at night. Even a "pro" shop hasn't figured out what's wrong and I've got over $800 in it over the past couple of years. All in all it's still a great truck, and well worth putting money into it. Money's tight and this just makes the most sense right now to me. As always with CK5, some great advice, Thanks guys!!!
 
Just keep in mind if you get one of those NOS axles with the 3.08s and the gov loc, that carrier may not work with regular old 3.73s. You may need to find what's called "thick cut" gears to work with the higher ratio carrier. But if you can't, you may be replacing the carrier anyways.

And the gov loc isn't horrible, especially for how you use your truck.

So, when looking for gears, look for some that will work for the 3.08 and numerically lower carrier.
 
if its line an open anything 2.73-4.10 should be the same. My axle originally had 3.42s in it, and the 8.5s in the second gen camaros swap from 2.73 on up no problem, just the 2.41 and 2.56 ones are different.
 
Random thought, and it may not matter to you, but the M1009 rear axle you're getting will be 28 spline axles and not 30 spline like your truck has now.

Just keep that in mind if you're ordering parts for it.
 
How much is interchangeable between these different setups? Supposedly I have 2 brand new axles in my current rear... It will be interesting to see what was REALLY done when the shop worked on it.
 
If the housing is warped then the axles may be fubar too...or at least one of them.

I believe the housings are the same but the axles, bearings, races, etc are all slightly different to accommodate the 30 spline axles vs the 28 spline.

A posi/locker will need to be correct for the axles too.
 
I was originally planning on trashing it all anyway, but figured I should check... In 21 years of wrenching on cars, engines, playing with fuel injection, etc.... This rear in this truck has been the worst, and I thought it would be one of the simplest things to fix.
 
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