First gear lock up in 722.3 C36 AMG? - PeachParts Mercedes-Benz Forum

JayRash · #1 08-25-2010, 11:55 AM

guys,
i need help figuring out how to make my C36 lock up its first gear like in the W140 500SE, I.E in my 140 (1995) if i put the leaver in the B position it will not sift into second even at WOT and even if it hits the limiter. the B position is nothing but an electrical switch that engages the kickdown function (plz correct me if i am wrong here). So what is it that keeps the gearbox from shifting into second if the leaver is in B?

I need this as it will be a serious advantage in auto X events and even in drag races as i can then hold the first all the way to almost 7K and that means higher RPM when it shifts into second.

thnx.

400Eric · #2 08-26-2010, 01:33 AM

My 400E also holds first as long as I want it to so I don't know what to do about your first gear.

I've already put in a call to the guy that owns/drives the C36 that I'm always racing to see what he does. I'll post what he tells me when I hear from him.
Regards, Eric

RBYCC · #3 08-26-2010, 11:49 AM

Quote:

Originally Posted by JayRash

guys,
i need help figuring out how to make my C36 lock up its first gear like in the W140 500SE, I.E in my 140 (1995) if i put the leaver in the B position it will not sift into second even at WOT and even if it hits the limiter. the B position is nothing but an electrical switch that engages the kickdown function (plz correct me if i am wrong here). So what is it that keeps the gearbox from shifting into second if the leaver is in B?

I need this as it will be a serious advantage in auto X events and even in drag races as i can then hold the first all the way to almost 7K and that means higher RPM when it shifts into second.

thnx.

Jay you may want to visit Benz World and message Jonathan Hodge ( Jono )...

I believe his shop in Atlanta USA has heavy duty clutch packs available for the 722.3 and he may have the ability to modify the valve body to possibly make it full manual...

Not sure, but worth a try...

Ed A.

JayRash · #4 08-26-2010, 12:01 PM

thanx for the heads up.

400Eric · #5 08-30-2010, 01:01 AM

I still haven't heard from my C36 guy yet.
I called and left another message tonight.
Regards, Eric

JayRash · #6 08-30-2010, 02:31 AM

eric, im sure he hasnt done anything special to the gearbox, the C36 valve body is really good and hold first till 6500 in first, and almost 7K in 2nd and 3rd. What im looking for is a way to force it to stick in first even if i liftoff at redline. that way i can control the car in tight auto-X corners and gain weight transfer.

the first on the AMG at 6900 is almost 75kph so its a tall ratio.

JayRash · #7 09-08-2010, 01:46 PM

Ok turns out to be very simple and this can be done on any 722.X gearbox. Our cars have the kickdown switch which connects a 12v to the kickdown solenoid in the gearbox. but to have the gearbox kick down a gear and then shift into the next at redline the power used to energize the solenoid comes from a relay like the fuel relay on the w124s. this relay reads rpm, and at a preset limit cuts the 12v to the solenoid even if the kickdown switch is still pressed flat.

I guess u can see how it goes frm here to have the gearbox hang on to first even at redline.

either feed the solenoid 12v from a source controled by you, or fit the gear leaver assembly of a w140 and have B position feed the 12v for u untill u shift out of it.

400Eric · #8 09-09-2010, 06:45 AM

I'm still going to try to find out what, if any tricks Brent is doing since I need to talk to him about our next track day anyway. We are just playing phone tag right now.
Regards, Eric

JayRash · #9 09-09-2010, 11:29 AM

ok today i connected a wire to the kickdown wire in the switch under the pedal and ran it to a hand held on / off switch that has constant 12V on it. i kept the relay in place. so now i have normal kickdown and kickdown when the switch is on. the car only down shift when the accel is depressed far enough but no need to floor it. saddly thou it doesn't seem to hold the first any more than if i had used the normal kickdown method.!!!

but when i remove the relay and jump pinns 15 and 87. if i floor it all the way until the pedal clicks the normal kickdown switch, it holds first on the limiter. but if i try to use my hand held switch it still doesn't work.!!! so my idea is only half successful.

will keep u posted.

edit:
Well i spent the best part of 2 hours testing several setups ( stopped when my trans temps hit 110'C) , with and without the relay in place.

so far i think the valve body of the W140 is what allows the car to shift into first gear without having the throttle depressed. any way i will study the wiring diagram of the w140 vs that of the 36 and see if the differances are just electrical / kickdown solenoid, or if it is further inside the valve body.

for now my car with the relay inplace has normal function, ie first shifts at max RPM of abt 6500. with my hand held switch in the on position first shifts out of first at almost the limitter of 6800. not bad for a drag race, as it shifts into second at a higher RPm. i still cant force it into first when i am at below 40kph and off the throttle.
half way thru so far

400Eric · #10 09-10-2010, 08:22 AM

I talked to my other C36 buddy today. The good news is he confirmed his intention to go to our next track day on 09/18/10.

The bad news is he's not gonna be much help here cause his car is working fine holding first till the rev limiter kicks in if he pushes it. That's just full throttle driving though as he doesn't let off to enter a corner like you do since he's just drag racing it only. I understand that you want it to stay in first even when you let off so you can have engine braking entering a corner but he doesn't do that kind of racing cause it's too expensive. He would like to but he said that a day at that kind of track is $150 vs. only $20 for a full day of drag racing. He' did offer a few suggestions but it looks like you have them covered already.

I do have one of my own too: Maybe that first gear solenoid went bad in the past and was replaced with a standard one for a regular W202? I know I'm really reaching here but I can't think of anything that you haven't already thought of.
Regards, Eric

JayRash · #11 09-10-2010, 05:11 PM

Eric thanx,

My gear box normally functions like the w124 300 u have but with first gear start from factory.
my soleniod is fine

any way so far i can rev it now in first all the way to 7K. Fair enough.

rodnex · #12 10-16-2010, 09:15 PM

just a hint:

the W463 350GD has the small 722.3 (as our M104)
and has also the 1st gear lockup.

Maybe it is a help for you

regards
Rod