How Much Power Can Mach 1 Auto Transmission Handle?

[SouthKak_Mach1]

How much power can the Mach 1 auto transmission handle? I'm going the forced induction route this year, so I'm trying to figure out what I need to upgrade to handle the extra power.

[AlloyPony]

I have two friends with 4R70W cars and blowers and both have suspected torque converter/trans. issues with the power. They're making 380HP on the dyno. We haven't torn either car apart to see what's really going on yet, but both cars started to get noticeably slower as the year went on and the engines were in great shape, so we figure the trans. just doesn't like the power.

[SouthKak_Mach1]

Originally Posted by AlloyPony

I have two friends with 4R70W cars and blowers and both have suspected torque converter/trans. issues with the power. They're making 380HP on the dyno. We haven't torn either car apart to see what's really going on yet, but both cars started to get noticeably slower as the year went on and the engines were in great shape, so we figure the trans. just doesn't like the power.

Thanks for the info!

[SouthKak_Mach1]

From what I've gathered from searching through old posts on M1R, the 4R75W transmission in my Mach 1 can handle 750 ft lbs of torque at the transmission (700 ft lbs for the 4R70W). If this is correct, I should be fine. Only looking to make about 600-630 RWHP with P1X Procharger kit and forged rotating assembly. If I decide to turn up the boost later on, I'll start looking at upgrading the transmission.

[AlloyPony]

I think that's for a fully built unit. The stock units were rated 550 lbs/ft of maximum input torque, but like I said I've seen issues with them with slightly less torque than that behind centrifugal blowers. If you're going with a roots style blower, that's even more shock load so hopefully yours will be OK but don't be surprised if it shortens the trans. life. Good luck with the project!

[fastlane]

Stock units are good for about 500tq because the torque convertor will multiply torque at the input shaft. If you are making 450-500tq at the engine, the input shaft will see almost 1000ft.

I am running a 4R75W in my car. I am making over 900hp/800tq at the tires. Knowing I was going to push the limits of the trans, I had it built before installing. Speaking with my builder, the biggest issues are the stock clutches, input shaft, convertor, line pressure, and sun gear shell. There also needs to be some additional oil cooling of the tail shaft. When my was built, we installed Alto Red Eagle clutches, billet input shaft and sun gear cage, upgraded bearings, and an external line to feed trans fluid to the tail shaft. If you want the clutches to hold, you need to bump up the pressure in the valve body. You can do things like the JMOD or install a shift kit to help. I went the route of having my builder rework the stock valve body to his specs in order to achieve the proper line pressures. Bumping the pressure can cause the stock convertor to balloon so I highly suggest getting a good aftermarket convertor or have one built to your spec. Mine was a custom built unit and I couldn't be happier.

Don't forget to install a good transmission cooler just to keeps things cool. Heat will kill the clutches and never do a WOT 3-4 shift at higher power levels, you will grenade even a built trans if you do.

[SouthKak_Mach1]

Originally Posted by AlloyPony

I think that's for a fully built unit. The stock units were rated 550 lbs/ft of maximum input torque, but like I said I've seen issues with them with slightly less torque than that behind centrifugal blowers. If you're going with a roots style blower, that's even more shock load so hopefully yours will be OK but don't be surprised if it shortens the trans. life. Good luck with the project!

Thanks for the info! Looks like I'll have put some cash aside for a transmission build before putting on the Procharger P1X kit.