TH350 Auto Trans Upgrade

All,

I have an automatic TH 350 that has some issues. It's a good trans with no leaks but I don't have low 1 or 2 and I don't like the shifter. I spoke to the builder and he thinks it's strictly a stock 350. I'd like to beef it up a bit.

Before I take it to the trans shop I wanted to get some ideas on what to do with the trans and shifter. The car won't be used for street racing or even that much hot-rodding. Actually I'd like to be able to drive down the highway at 70mph at less than 3000rpm. So, I understand that the rear end may also need to be looked into. I don't have all the specifics on the engine, but it is a built Chevy 350, bigger pistons, "police" cam, and improved head assemblies. That's really all I know about the engine. Not sure what the HP is.

The builder told me I needed to put in a shift kit in the trans and replace the shifter but, he didn't provide me any suggestions. I can ask the pros at the trans shop and I'm sure they can get me fixed up with what I want but, I want to get some input from the field as to what set ups work best. Right now 65mph is about 2800rpm so the rear end may be fine.

I know this is a broad topic but I look forward to any input.

Thanks!

rob

With a mild 350 engine a stock rebuild on a 350 trans should work just fine for you. If you install a "shift kit" that will increase internal pressure to speed up the shifts between gears. It will feel more "sporty" and slightly lower operating temps. If you like to be able to leave rubber in 1st, 2nd, and 3rd gear and don't mind a little jerking back into your seat than a shift kit should work great for you. Make sure you have plenty of cooling capacity for the trans; these Sebrings get pretty hot underneath. If all you plan to do is shift into park-reverse-drive then a stock-style shifter will work fine. But if you want to be able to manually shift gears with your shift kit then you will need a heavier duty racing style shifter. Don't forget to take into account how shifter choice will affect the interior style of your car.

Good advise! Thanks. I'll keep this in mind when I speak to the trans shop.

I've had good luck with the B&M Mega shifters. They are ratchet shifters that will only move one position no matter how hard you hit them. Sometimes called a slap shifter. They ratchet up and down. Not cheap but they will keep you from missing a gear.

You need to figure out your rear gearing. That is why your RPM's are so high. Sounds like you have something in the mid to high 3 to 1 ratio.

You might consider ditching the TH350 and going with a 700R4 overdrive trans. Discuss the cost with you trans guy.

Thanks again Hotrod. I'll ask about the 700R4. That may be a good option depending on the cost.