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3.08 to 3.55/3.73 Rear Change
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Bonger
New User
| Posts: 3
| Joined: 09/09
Posted: 09/30/09
06:14 AM
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Hey Guys.....first off, I'm working on a 71 GMC truck and not a car but I figured that alot of you will probably have answers for me.....
Right now the truck has a 355 rating around 425hp and a 3 spd Turbo 350 Trans. I want to get better pick-up in it and it doesn't do a ton of highway driving so my MPG's aren't a major concern. Currently it has a 12 bolt with a 3.08 ratio and I want to go to either a 3.55 or 3.73 (still want to be able to take it out sometimes on the road so I don't want to go 3.90 or 4.11!!!)
Question is, can I change the ring gear and pinion on the current rear end? And if this is possible what size of ring gear will fit the case (8.875"???).
OR, do I have to upgrade to a whole new differential assembly??? I know I can use one from another truck but can I also use one from a car off say a full-size GM(Impala/etc)???? Also, the truck has coils and not leafs.
- Any suggestions or opinions would be greatly appreciated! Thanks Guys!!! And even though I know this is probably a question thats been beaten like a dead horse.........but what kind of improvement will I get from the 3.08 - 3.55/3.73 swap?
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Posted: 09/30/09
03:32 PM
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I would install a 3:42 gear myself and yes you can use your current rearend housing. I would recommend you get an install kit with the gears it will have all your bearings,seals,gasket and marking compound.
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Posted: 10/01/09
05:32 AM
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i run 3.73 posi with a 3 speed th350 and 450+hp 383 and they give good drivability doesnt seem much different than my daily driver at 45-50
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