3.08 Rear Gears

[79bird]

I have a '79 Sunbird with a 4.1 v6, an Isky cam 2 steps over stock with matching valve springs and a mild port job. I have a Q-jet from a '79 Turbo Regal. The car goes about 2,900 lbs. Right now I have a TH350 with 2.73 gears. I want to put a 200-4R and 3.08 gears in. My question (finally ) is would I have to worry about the motor bogging down with the gear ratio or should I think about 3.42's?

 

[22lbChevelle]

Im rolling on 2.73s with a 3.8L and 200r4, I never bog. Just today I showed my dad how I can climb hills with the converter locked at 1200rpm. Without the converter locked you literally will never bog. Even when i lock the converter and cruise at 1k it doesnt bog, it just doesnt make any power lol.

 

[fuzzyGN]

Don't forget to factor in the tire height. The shorter the tire the higher numerically the gear equivalent. On my Vega I have a 25.5 tall tire (about 1/2" shorter than stock TB) and a 4.30 gear. The tire height makes the gear set "act" like 4.56. So, the 3.08 gears with the really short tires you probably have on your car will act closer to a 3.23 or more. You will be fine. Not only that, finding 3.42's for an H-body 7.5 rear isn't easy. I have all of my standard gear set pinions machined so they work in the H-body housing.

 

[79bird]

No Bog - Good

I'm going to wait and see what happens, I may be in the wrong forum here as I have a NA motor not a Turbo. When I get it I'll hold on to the 3.08 gearset just in case. I know there are places out there that make a thicker 3.42 ring gear to fit the 7.5 series two carrier I have.

 

[fuzzyGN]

True but there is no place currently that makes new 3.42 gear sets to fit the H-body (Vega, Sunbird, etc.) rear housing. The pinion is a different diameter. The pinion can be turned down to fit a new bearing or there is a hybrid bearing to use the existing pinion size in the smaller housing but the longevity isn't very good. either way the standard 7.5" gear set is not a drop in deal.

 

[charlief1]

True but there is no place currently that makes new 3.42 gear sets to fit the H-body (Vega, Sunbird, etc.) rear housing. The pinion is a different diameter. The pinion can be turned down to fit a new bearing or there is a hybrid bearing to use the existing pinion size in the smaller housing but the longevity isn't very good. either way the standard 7.5" gear set is not a drop in deal.

Not always true Eric. I've done a little research on the gear issue for the 7.5 and it seems that GM made a slight boo-boo on sizing the 7.5. It's really a 7 & 5/8" ring. If you've got the 6.5" you're screwed but all the 7.5 and 7.625 gears are the same.:biggrin: You can get some bearing to adapt it if you need to but it shouldn't be an issue.

 

[dr_frankenstein]

Not always true Eric. I've done a little research on the gear issue for the 7.5 and it seems that GM made a slight boo-boo on sizing the 7.5. It's really a 7 & 5/8" ring. If you've got the 6.5" you're screwed but all the 7.5 and 7.625 gears are the same.:biggrin: You can get some bearing to adapt it if you need to but it shouldn't be an issue.

This does not apply in the H Body Charlie.

As close as it seems it is to a S10 Rear, there are differences.

They do not directly interchange.

I believe the reasoning behind this was that the load rating for the H-body was much lower, Thus didnt need as beefy of a pinion.

ALSO: 79BIRD

if your running the Turbo Q-jet on a NA car... the calibration is all wrong, change out the carb.

A.j.

 

[79bird]

Q-jet wrong?

Would the jets and metering rods be wrong? Would it run too rich?

 

[fuzzyGN]

The H-body 7.5 rear housing is unique to the H-body. They are identical to the S-10 rear in every way except for the suspension mounts and the pinion diameter. In fact, everything in my current rear in the Vega was ordered for an S-10 (28 spline axles, locker, gears, bearings, shims, etc.) with the exception of the pinion bearing. That is H-body specific. Then I took and machined down the pinion diameter until it was a slight press fit with the new bearing. All else goes together like any other. I have had a dozen of these freaky little cars and have yet to find on that does NOT have the smaller pinion. Even the factory V8 cars had the smaller pinions. If they didn't get the "normal" size then I doubt any others would. Hope that helps clarify a little.

 

[79bird]

Hey Erik, I've been following a lot of the threads over on V8Monza.org about using the S-10 parts. I'm following a train of thought that figures a 3.42 gearset would be best for my 4.1 and future 200-4R install from a performance and economy balance. I can get a 3.08 rear end off a '92 2wd. S-10 and I thing it'll be ok for my purposes. The 2.73's may be a little too high but I'm sure the 3.08's will be fine. I'm asking on this site to get a second opinion of sorts. And yes the pinion will have to be turned down or I can use the Conversion bearings but that's a whole 'nuther thread.

 

[79bird]

that's H-body.org, not V8Monza.org

 

[fuzzyGN]

Yep, as I stated way above I think the 3.08's would work well for a driver. These cars are super light so they don't need as much gear. The only reason I have so much is the engine I have now. Not exactly daily driver worthy but still hits the streets on cool nights.

 

[dr_frankenstein]

you wouldnt happen to need a 5 lug swap kit for the front of the H-body would ya?

LOL

theres an easier way now then chopping up the lower control arms.

A.j.

 

[79bird]

I did the 5-lug swap a long time ago, Got all the parts from an s-10 and a mid '80's Grand prix. I am going to change out the bearings and races to all new ones. I don't trust mixed and matched bearing parts.
Please explain what you mean by 5-lug swap kit, what parts are involved?

 

[fuzzyGN]

He probably means all the parts he bought from me . I originally had stock lower control arms modified to fit the G-body spindles and uppers to match. I didn't use them because I went with Aerospace stuff instead (much lighter). Sold the old stuff to him. It actually is a pretty sweet setup and much better than the ball joint spacers.

 

[TURBOPOWERED68]

i have 3.08s and they suck, OF the line the car is a dog compared to a similarly built car.
But your car is much lighter so it may not be so bad.

on the flip side they have GREAT HWY manners.

 

[79bird]

While I like watching it, I don't intend to do any "off the line" shots with this car. It is only around a 2800-2900 lb. car so it won't be too bad. I told the guy with the 3.08 S-10 I'm not taking those gears. I'll wait until I'm ready and get 3.23's or 3.42's with posi.!
dr_frankenstein could you send me a pic of the upper control arms and how much you want for them? I allready have the lower ball joint spacers so I'll keep that the same unless I get info on a better setup. I would like to get the correct setup for the upper. Camber and Caster and all that stuff. Plus it's a cast iron pain in the a*# to change the lowers. Even though I know I'll have to do it someday to free up the cam bolts. And to clean them up to have brackets welded on for a 1" sway bar.

 

[dr_frankenstein]

He probably means all the parts he bought from me . I originally had stock lower control arms modified to fit the G-body spindles and uppers to match. I didn't use them because I went with Aerospace stuff instead (much lighter). Sold the old stuff to him. It actually is a pretty sweet setup and much better than the ball joint spacers.

just the lower control arms, everything else I used. I dont need them for the skyhawk with my new adapter system.

A.j.