How Much Power Can Mach 1 Auto Transmission Handle?
 

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.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

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.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

Thanks for the info!

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

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.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

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!

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

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.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

Even with added power go with a higher stall converter. Better that's stock unit and will really wake the car up that much more. I had my p1 in there but was amazed at the difference adding a higher stall converter. I went with a PI unit but there are others out there. A better converter will let you rev higher too.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

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

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

Thanks for the advice! Checking out stall converters now.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

Thanks for the info! Will definitely have to build my transmission.

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

Good info here. Generally I think they are a very decent trans. I have rebuilt a few 4r70s and added minor upgrades with good results. They are very straightforward to work on.

One issue I've had with the J-mod, particularly on one unit, is that the 1-2 shift was quite a bit firmer but not crisp. Almost like there was still shift overlap. If I can't get rid of the overlap, I'd rather not have done the J-mod.

I'm about to go the thru the trans in my Black '03. I've heard that the J-mod is pretty much already done on these units, with the possible exception of the accumulator springs. In other words the holes in the separator plate are supposedly already opened up. We shall see soon.

Has anyone else here used a different shift kit and what were the results? I don't mind firm engagement into drive and reverse. And I like firm shifts but they need to be crisp.

This car is just getting an all-over refresh and mild power mods. Basically a solid car that can be driven without much thought. It would be nice if it would chirp the 1-2 shift :smokin:

Re: How Much Power Can Mach 1 Auto Transmission Handle?
 

Anything over 500 rwhp and it's on borrowed time, I have two cars that run 4R70w, when my Marauder had a trilogy and was making 440 rwhp it was fine, once I ramped up the power I went and had it built with hardened input and output shafts and with extra clutches in the drums also a good shift kit, today it holds 680 rwhp plus with the stock torque with no issues.

My other in now in the Mach build I have going on but came out of my GT car that made over 700 rwhp and it too is built the same as the marauder one with the exception of a Circle D convertor.

Both cars I might add have external coolers on them.

The tuner play's a big part in the trans life cycle, having someone that knows that trans and can tune it will make a huge difference.