79 Diff gears
Thread Starter
5th Gear
Joined: Aug 2002
Posts: 5
Likes: 0
From: Evansville IN
79 Diff gears
My dad has a 79 that he has done a little work to add some power. He wants to go with a lower ratio in the rear end. How do I find out what the current ratio is? Will any GM gears fit into the carrier or do they have to be from Vette.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Re: 79 Diff gears (andyglines)
You check it mathematically on Smokemup.com
I thought of doing this. Then I discovered that long-term I was better off putting the money into a 4-speed automatic instead.,
I thought of doing this. Then I discovered that long-term I was better off putting the money into a 4-speed automatic instead.,
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: 79 Diff gears (page62)
There are numbers stamped into the rear carrier but if the y have been changed you are out of luck. Jack the car up and mark the tire and drive shaft. Have someone rotate the tire exactly one turn. Count the number of times the driveshaft goes around. if it goes around 3 times you have a 3.08, 3 1/4 times 3.36, 3 1/2 times 3.55,3 3/4 times a 3.70 4 times a 4.10 and so on. This is the easiest and most reliable way aside from taking it apart and counting the teeth.
Thread Starter
5th Gear
Joined: Aug 2002
Posts: 5
Likes: 0
From: Evansville IN
Re: 79 Diff gears (page62)
He's actually done more than a little work to it. Its got a 400 sb with a B&M supercharger. It has been tubbed and has some pretty big meats. He just put the Th400 in because he smoked the 700R4. The gearing is now a little to high he wants 4.10 or 4.56 now. Will any GM gears fit in the Vette diff?
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: 79 Diff gears (andyglines)
No they have to be gears for the Vette. They won't fit anything else but the Vette. If he is going to run a 4.11 or 4.56 he is either going to have to use a 4 series carrier or special gears that fit on a 3 series carrier. The ones that fit a 3 series are thicker to compensate for the smaller pinion gear. If he wants a 4 series carrier I have a good used one for sale. I had a 4.11 gear with a spacer (not the thing to do) and was going to install the 4 series carrier. I blew the rear before I put in the 4 series and went to 3.70 gears. Let me know if interested
