duescherc

I am going to have my rear end gone through, and I was looking around at new ring and pinion gears to have put in; either 3.70 or 4.11. The car is a 72 with a stock 3.36 ratio currenly. When looking at different gear manufacturers, Richmond gears say that when going to 3.55 and up numerically you need to replace the differential carrier with a stock 4.10 or higher unit. Wondering if this is the case with most aftermarket gear sets for the c3, or if there are gears that anyone else has used that don't require changing the differential carrier.

63mako

Actually the 4.11 and up require a 4 series carrier if you use stock gears. There is a spacer available to compensate for this or US Gears has a thicker gear set to use in the 3 series carrier. Richmond also makes a 3.90 gear set. The US gear sets are cheaper to buy than the richmonds. You can check here for parts and info.
http://www.tomsdifferentials.com/201...Pages14-23.pdf

76strokervette

I have a set of 3.70 motive performance gears that will go in my 76 later this year.And yes they are made in italy not korea.
( i called before i bought them)My friend with a racecar chassis shop
said the italian gears are good.Summit racing has them in stock.

JohnRR

I like the 3.73 set with a wide ratio 4-speed. Any higher than that was lots of fun, but on a daily driver without an overdrive, the 4.10's and 4.56's got old.

John

rponfick

Mako, could you elaborate on spacer use and thicker grear requirements. Not sure I understand when you would use them. I am planning to change from 3.08 to 3.55 Richmonds in my '72, and hoped it was a simple change.

Thanks, Ralph.

63mako

If you go from 3.08 up to 3.90 no spacer or thicker gear needed, easy swap. if you go from a 3.xx to a 4.xx ratio you need either a spacer or a thicker gear if you don't change to a 4 series carrier. If you have a 4.xx stock gear and want to go to a 3.xx you need a 3 series carrier as your 4 series carrier won't work.

JohnRR

I believe the rear gear system goes like this. As you numerically increase the ratio from a 3.08 to say a 3.73, the pinion gear gets physically smaller in diameter. Therefore, the corresponding ring gear has to get thicker so the gear teeth mate properly. Following this line of reasoning, a 4.10 ring gear would have to be even thicker, so the carrier is changed to a 4-series which brings the ring gear mounting surface closer to the pinion, and hence a thinner ring gear. Or you can stay with your 3-series carrier and use a spacer behind the new 4.10 ring gear.

John

rponfick

Excellent explainations. Now, even an old person like me can understand. Ralph.

rponfick

Mako, I'm back. Just went on Jegs website to order some 3.55 Richmond gears for my '72. Part no. 4900211. When I put the part no. in the search box, it brings up the gear. If you hold your cursor over the more details area on the left side of the screen, it brings up the following comment "When replacing a 2.41 to 3.70 ratio with a Richmond ring and pinion, the carrier must be replaced with a carrier from a stock 4.10 or numerically higher".

This sounds like the question raised by the original poster. He must have been reading the same website.

What do you think is going on? Can the Richmond gears be a little different? I don't see any cautionary comment on the Summit website. So, I guess that is where I should order from and avoid the issue.

Just curious. Ralph

63mako

Order from Tom's. They specialize in the corvette stuff, will make sure you get the right gears for your application, and probably the same price.

rponfick

Just tried to call Tom's. I didn't realize northern Idaho is on Pacific time, and the answering service person said the roads were terrible. So call back much later.

I was hesitant to call Tom's because his website shows Richmond gears at $50+ more than Jegs/Summit. But, I'll give him a chance.

Thanks, Ralph