1986 Jimmy 4x4 3.4 - Question on Diffs

[pappyl]

Not a pro on diffs.

Anyone know what the ratio is on the 1986 4x4 (had 2.8)? Tell by the VIN?
Are they 3.42?
Thinking of going low to max my mileage. I believe I'd need to swap both the front and the back to keep them in synch - correct?

Appreciate help.

[steve]

Not a pro on diffs.

Anyone know what the ratio is on the 1986 4x4 (had 2.8)? Tell by the VIN?
Are they 3.42?
Thinking of going low to max my mileage. I believe I'd need to swap both the front and the back to keep them in synch - correct?

Appreciate help.

Well, you need to change both for sure. To find out you ratio you need to check the sticker inside your glove box.

The RPO codes are as follows

GU4=3.08
GU5=3.23
GU6=3.42
GT4=3.73
GT5=4.10
HC4=4.56


There is a G80 locking differential that also came in some of the trucks. Someone will need to clarify whether or not the Zexel torsion diff was a factory part on the s-10's or if the locker was a clutch style.

Quoted from: blazinlow89 (http://mys10.com/member.php?u=4120)

[Rinkrat456]

Thinking of going low to max my mileage. I believe I'd need to swap both the front and the back to keep them in synch - correct?
In a 4x4, both gear sets in the differentials need to match. Chances are you have 3.08's already but check your glove box for sure, 3.42's are definitely a possibility.

When you say you want to go "low", do you mean change your ring and pinion set to a lower numerical number (example going from 4.10's to 3.08's) or do you mean you want a lower gear set to increase power to the wheels (example going from 3.08's to 4.10's)? Technically, 4.10's are lower than 3.08's.

[Donahue]

my 89 had 3.73's (2.8)

[pappyl]

Thanks guys... Will check my glovebox.

Yeah - low meaning ratio - 3.08 for more mpg...

I didn't know about the locker.... didn't notice if it locks, but could. Already went off road (not on purpose) Climbed outta that ditch pretty good.
1st time in 15 years I lost it. Had 4x4 on, hit ice and gusty wind. These Jimmy's have a real close wheelbase I'm not used to. (ie: I'm a pickup/suburban guy - smallest vehicle I've owned - lol)
I fishtailed for at least 500', kept over correcting, just couldn't keep her straight. At least I was able to stay off the damn brake. Tends to go by pretty fast.
Damn little bugger.

[klr650]

My 86' 2.8 had 3.73s 4x4. It also had a GM factory limited slip posi. This posi is different in that it has little spinning weights and little tiny springs with little tiny interlocking gears and cogs, ALL INSIDE THE CARRIER. I was told that it was a prototype locker that was only offered for 3 yrs in select s10's and one car.

People that are knowledgeable on this locker will know that it is not rebuildable and when it wears out, it will become A DANGEROUS SITUATION. It has the reputation of getting people killed.
The spiders in the locker will jam at anytime, anywhere, full throttle, no throttle, with no warning at all except the fact that your face is in the windshield and your sliding sideways down the highway.
Mine now resides under my work bench as a conversation piece after it tried to take me out.

[Rinkrat456]

Sounds like the Eaton Gov-Lok to me. Haha it did the same to me on the highway.

[Donahue]

yeah, thats the gov-lock, its really more of a locker than a posi. its been available in lots of trucks from the 70's through today. the 14b in my 94 burb has one, and i know they came in at least 14ff, 8.5" 10b's and 7.5" 10b's. i would be willing to be that they put one in the 9.5" 14b too, i dont know about the 12b though.

i call it a locker because when it locks, it is truely locked but i wouldnt put it in the same class as say a detroit.

[Rinkrat456]

It's a mechanical locker operated by cam ramps and flyweights that engage the other axle shaft if a wheel speed of 100rpms difference is detected. The "G80" is available in all truck applications, from the 7.5" c-clip to the 10.5" full floater, as an alternative to an open differential. Some 14bolt rears though, came with the Detroit locker from the factory, modified slightly by GM to have more daily driver manners.

[67Truckin]

Looking thru my old sales flyers, it looks like the majority of the 4x4 S-10's with the 2.8 V6 engine had 3.73 gears in the axles and used either 215 or 235 tires.

[Donahue]

It's a mechanical locker operated by cam ramps and flyweights that engage the other axle shaft if a wheel speed of 100rpms difference is detected. The "G80" is available in all truck applications, from the 7.5" c-clip to the 10.5" full floater, as an alternative to an open differential. Some 14bolt rears though, came with the Detroit locker from the factory, modified slightly by GM to have more daily driver manners.
i call BS on GM "slightly modifying" the detroit. ive owned a factory detroit 14b and it was in no way different than the other detroits ive dealt with for the 14b