3.70 Diff
Thread Starter
Instructor
Joined: Apr 2006
Posts: 243
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From: Canton MI
3.70 Diff
I have a 73 L82 4-speed that has a stock 3.70 rear end. I haven't had it apart yet and I'm what yoke it has (number of splines). I'm considering changing out the gear set to something taller to get the revs down at higher speeds. I have a leaky pinion seal and the lube needs to be changed so Id rather do all this at once while its apart.
Tech Contributor
Joined: Aug 1999
Posts: 15,135
Likes: 3,939
From: Connecticut, USA
The spline count is the same from late 63-79. The yoke width is different between soem 4 spds and automatics. If you're going to re-use the same yoke you'll be ok. The best gears to use are Tom's. I do a lot of these so if you need help let me know. Good luck.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
If your rear is fine (in the car that is 
) then you might look into a 5 speed, I put a T5 in my 73 with 3.70 and 80 mph on the e-way is less than 3000 rpm's now but still got the get up and go outta the hole.
) then you might look into a 5 speed, I put a T5 in my 73 with 3.70 and 80 mph on the e-way is less than 3000 rpm's now but still got the get up and go outta the hole.
Racer
Joined: Aug 2002
Posts: 289
Likes: 0
From: Albuquerque NM
Originally Posted by torqvette
3.70 Diff, 27" Tire, T56 (.5 OD) 1850rpm @ 80mph
Thats barely over idle in mine.....I dont think my car would work at all with that low a 5th.....LMAO....dang.....how fast are we going when the rpms are at 64oo?
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Melting Slicks
Joined: Sep 2004
Posts: 2,412
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Gear limited to 270mph @ 6200rpm. But I'm guessing that my car's top speed would be horse power limited. 
6th gear is great for cruising on the highway. I'm going to swap in some 4.11s or 4.56 this summer so that I'll never be able to get traction.
Even with 4.56 gears it would be less than 2000rpm at 70mph.
And with the automatic on the freeway it was horrible. I was always 3500+ rpm on the freeway.
6th gear is great for cruising on the highway. I'm going to swap in some 4.11s or 4.56 this summer so that I'll never be able to get traction.
Even with 4.56 gears it would be less than 2000rpm at 70mph. And with the automatic on the freeway it was horrible. I was always 3500+ rpm on the freeway.