Differential swap?
Thread Starter
Instructor
Joined: Jan 2008
Posts: 138
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From: Deland FL
Differential swap?
I have a 1972 Heavy Duty Differential (original to my car) with 3.08 gears..I was wondering if changing to a later 77-79 Standard Differential with 3.70-4.10 gears would be a wise choice..I have a 3200-3500 (tight) stall converter..RMVB 400..and a Holley Strip Dominator, mild cam, and holley 650hp..and I'm right about 10:1 compression in a 355..can I live with the 3.08s or is it better to have a weaker rear with better gears?..I don't have much money to modify things.right now so buying a rear or gears will really set me back...FWIW..I also have the stock motor and TH400 from the car too, but I would really like to use the mild 355 setup ..just wondering if the car is going to be slower than stock, or a dog to drive with 3.08 gears?? thanks
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
I have a 74 with a similar set up. The cam comes in around 2k . With stock converter and 3.08 it was only fun from 70-100mph. 2800 converter would spin tires about 5 feet. I bought a 3.55 diff from a 78car and it transformed the car. Lost some top end but its much more fun. Car is about 350 Hp.
Le Mans Master
Joined: Jan 2006
Posts: 6,504
Likes: 139
From: Butler Pa
I have a 1972 Heavy Duty Differential (original to my car) with 3.08 gears..I was wondering if changing to a later 77-79 Standard Differential with 3.70-4.10 gears would be a wise choice..I have a 3200-3500 (tight) stall converter..RMVB 400..and a Holley Strip Dominator, mild cam, and holley 650hp..and I'm right about 10:1 compression in a 355..can I live with the 3.08s or is it better to have a weaker rear with better gears
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 330
From: Indy Indiana
as my understanding goes, your heavy duty rear end's only difference is the yokes connecting to your half shaftes are connnected by straps and not u bolts, plus you will have a rear stabilizer .. so all you have to do is use your heavy duty yokes... the pumpkin case is the same, the gears are the same hardness, the bearings are the same, the posi clutch packs are the same. gear ratio does nothing to make it heavy duty..
just put your yokes in the other case and you should have equal durability.
how do you know your 72 is HD?
just put your yokes in the other case and you should have equal durability.
how do you know your 72 is HD?
Thread Starter
Instructor
Joined: Jan 2008
Posts: 138
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From: Deland FL
thanks for the replies..that's really a bummer, that the gears effect these cars that much.I have a 77 Trans-Am with 400/TH350/2.41 gears and even mostly stock, that thing was fun..well I guess I will just leave the motor stock, and try to get a different car for my motor combo..I don't have the later gear set, and I was just going to swap the pumpkins not looking forward to changing it anyway...I'm pretty sure mine is a HD Rear stock, it has the caps..and nothing has been changed it's an AW code rear.in an AC coupe..it's not a Big Block rear so no rear bar..Thanks Again for the replies.
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
I thought of another difference. The rear spring width is different, the 78-79 had a 2.25 in steel spring vs a 2.5 in. in your 72. You can just use the back cover from your 72 and be fine.
if you trick the Vette...
Thread Starter
Instructor
Joined: Jan 2008
Posts: 138
Likes: 0
From: Deland FL
well I am going to be keeping the vette, I just don't know if it will be better to keep it stock or not..My cars body is far ,far from stock. I have what I believe is a Motion Can Am Phase III body kit, we are in the process of restoring the car, and I was really hoping to have an engine to match the image of the car, but I may end up leaving it like it is, since all the numbers match..so Idk..Thanks for the info.
Le Mans Master
Joined: Jan 2006
Posts: 6,504
Likes: 139
From: Butler Pa
well I am going to be keeping the vette, I just don't know if it will be better to keep it stock or not..My cars body is far ,far from stock. I have what I believe is a Motion Can Am Phase III body kit, we are in the process of restoring the car, and I was really hoping to have an engine to match the image of the car, but I may end up leaving it like it is, since all the numbers match..so Idk..Thanks for the info.
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Thread Starter
Instructor
Joined: Jan 2008
Posts: 138
Likes: 0
From: Deland FL