transmission & rear end upgrade

I'm going with Motorheadmike on this - 400 hp is a lot but your estimating and we haven't heard any specs on the motor. If you are putting down 400 Hp a couple things are in your favor, it's probably got a good size cam which aren't noted for bottom end along with a stock convertor your not going to be punishing that rear too bad, and the fact that its a street car w/ street tires tells me go for it. The 200 4r is a tough trans and can be built to handle a lot more. I think you guys have ironed out the carrier spline question - If anyone is interested I have a 2002 S-10 rear end out of my Sonoma project w/ 4.10 gears I'll sell for $100

Bar50 said:

Because they are two totally different rearends?

The 26 spline had been in service since the 7.5 came out in Vegas and weak-sauce Nova six cylinder cars.

Monte SS cars did not break rearends religiously. Not real sure why or how the 442 ended up with the 8.5 though.


*You could get an optional 4.11 ratio in Monte SS cars.

The ONLY 28 spline axles that fit are 8.5 G-body axles, there is NO junkyard mystery swap.

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in an F body forum they talk about switching the 26 spline side gears with the 28 spline side gears and bored the hole on the carrier to fit the larger diameter axles

pontiacgp said:

in an F body forum they talk about switching the 26 spline side gears with the 28 spline side gears and bored the hole on the carrier to fit the larger diameter axles

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I guess I don't understand the reasoning, 28 spline posi units are pretty easy to find new and used? That machine work would have to cost what a used posi carrier would cost?

MrSony said:

So, to reiterate this back and forth nonsense, the 80s monte SS got the OPTIONAL 7.625 rear end in 1985, with 26 spline axles, with a range of different gear ratios (I don't know them all other than 3.42, 373, and apparently 4.11), and the 7.625 only got 28 spline axles in 1988, the last year of the g body monte SS... right? Man the OP of this thread's gotta be annoyed, eh?

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From everything I have got from GM resto program that has the dealer & production info, the '83-'85 had 3.42 gears & '86-'88 had 3.73. There was never a 4.11 during the '78-'88 production run. As for the 7.5" to 7.625" "upgrade", it looks the of been part of the '85-'86 change over.

pagrunt said:

From everything I have got from GM resto program that has the dealer & production info, the '83-'85 had 3.42 gears & '86-'88 had 3.73. There was never a 4.11 during the '78-'88 production run. As for the 7.5" to 7.625" "upgrade", it looks the of been part of the '85-'86 change over.

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This is as correct as I have ever known it to be.

The only performance axle ratios ever made available to the general public in a standard production G-body (ie. nothing special ordered internal to GM executives) have been: 3.42 and 3.73; and depending upon the year and/or model they came in either a 7.5"/7.625", or 8.5" ring and pinion axle housing. The only factory stock differentials to hold 28 spline axles were the 8.5" rear ends.

It is pretty straight in my mind.

Bar50 said:

I guess I don't understand the reasoning, 28 spline posi units are pretty easy to find new and used? That machine work would have to cost what a used posi carrier would cost?

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damn, I was hoping you could explain that to me, maybe it has something to do with mullets...