Bullet Proofing the 722 Transmission.
 

What can be done to strengthen the 722.3 and 722.5 (overdrive) transmissions.
I intend to do a few upgrades to put a few more horsepower to the wheels and I would like to ensure the least amount of problems.

I have a 87 300SDL with a 722.3. I intend to put in an intercooler, change the turbo to a larger Variable Geometry unit, possibly have a performance modification to the IP and put in a 722.5 five speed.
If I do everything the total HP should stay below 300 probably about 250.

All in all a lot of work but it should be fun.

My concern is that the Variable Geometry turbos make more boost at lower rpm nearly eliminating the turbo lag, but also making more torque at lower rpm which as I understand it is harder on the transmission.

I think the transmission will be the first part of the project. I know that I can get a 722.5 with the shifter and controller,(I think the price I’ve been quoted is a bit high but it is doable if I cannot find a better deal). I think I may need a speed sensor from the donor car to feed speed info to the electronic overdrive controller but am not sure on that part yet. The drive line will need to be shortened, that’s easy.

So how does one bullet proof a 722.? transmission? What parts and were do you get them?

The 722.5 trans WON'T take that much HP no matter what you do to IT!
The rear clutch(s) & plantary is too small & will fail under high torque applications!

400 hp automatic W124 om603s
 

There was a thread here a year or so ago about some nuts in Finland who were pumping 400 hp thru their automatic W124 om603s. There was video to support their claims.

If you check archives you could probably find their email and ask them how they made their trans last.

I'm putting over 345 RWHP and 400 RWTQ to my 722 tranny.

The 722.3XX can be made to handle quite a bit of power..Especially that later 722.350 & 353 come set up to take 333hp from the factory.

I have also heard of people installing an additional clutch plate (I believe the transmission in my black coupe is a 722.350 w/ 5 plates over of the stock 4).

The 928 guys are putting 5-700Hp through their 722.3's.

I've heard the same thing MB Doc mentioned about the 722.5..thus why I'm looking to install a manual:)

Jonathan

I need a bit of clarification. The 722.5 is the same as the 722.3 with the addition of an electronically controlled overdrive unit on the back, is this correct? When you say that the 722.5 cannot take the HP The overdrive components are undersized?

Is there an alternative transmission for the 603 engine that you could recommend?

Where can I get specific info / parts for hardening a 722.3?

Yes, I had read this and also the English posts on the Finnish forum. They were putting their efforts into HP generated at higher RPMs, if I go ahead with a Holset VGT turbo (Garrett calls there’s VNT) I will making more torque and HP at lower RPMs and this (as I understand it) puts more strain on the transmission than the same torque and HP at a high RPM.

Did you do anything special to the trans?

Thanks

The 722.3 will take that much & more torque! The 722.5 is a varient of the 722.3 BUT the ks clutch & rear plantary is too small to carry that much power!!

THE OM603 came with the 722.3_series trans!

No.

It certainly will be a lot easier not to replace a perfectly operating transmission. I was kind of hoping that I could put in a 5 speed …..oh well. Any other ideas for getting the rpms lower at 80mph and still giving you a good launch?

A 2.47:1 diff x ~a 3.6:1 first gear on around a 25" tire should still launch pretty well. Remember turbos are load dependant and it could actually be a bit better due to loading the turbo in first gear. Also the gear will be more "useable" as it won't upshift at 8-12mph or where it does currently from 1-2.

If you haven't yet, turn up the ALDA on the IP and check to see what your current boost levels are... I've read and seen these cars were running lower boost than stock and less fuel than stock from the factory. That will help it get off a stop light and into the boost.

Once you do that, install an EGT gauge and you could turn up the full load stop on the pump to get even more from it for now (until you strap on the IC).

Maybe I am reviving a very old thread, as some of you have read about my 722.5 ECU tranny problem, and what states in this thread is that the 722.3 (I guess that of the 300E 12V), so does it solve the problem if I install the 722.3tranny in my car? do I enjoy the last gear ratio similar or near the overdrive of that of the 722.5 ?

No, it's just a 1:1 in the .3, no OD.

Jonathan