1. Can you interchange the speedo gears in a TH350 with a TH400 and vise versa?

2. What speedo gears came in the TH400's of the 396 and 454 Chevelles when the rear gear was a 4.10?

Thanks.

Dawg -
I gave the guys at P.A.T.C. Speed Shop a call. The are located in Bossier City LA. They have a website it's www.transmissioncenter.net. Somewhere on there they have a calculator or you can give them a call. They did the calculations for me and sent the perfect gears. Great pricing and customer service. I had tried others before and had all but given up on finding the perfect set until I stumbled acoss these guys. Just as a reference I don't know the answer to your question but I have a TH350, 4.10 gears and 28 inch tall tires. I needed a 21 tooth driven gear and a 7 tooth drive gear. I'm not far away from them but I recieved the gears the next day.

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

I "think" the gears and bullets from the 60's are all the same.
I "know" you can pull one out of a powerglide and plug it into a muncie.

Hey.....just curious but did certain TH350's come with certain color code drive gears?

Right now my speedo reads 20 mph faster than it's really going.