yah, 3 seconds won't hurt, BUT

3 seconds, 15 times in a half hour period, every other day, for a year, THAT will do some damage.

3 seconds, once every couple weeks, for 20 years, your fenders will probably fall off the car before tranny complains.

__________________
-Matt

EPA Section 609 Certified MVAC Technician
-----------------
Oil Burner Kartel Member #10

Ahh the smell of Diesel Fuel, it's like coffee in the morning!

My Car:

1982 300SD Turbo Diesel (231,500 miles!) RIP

1984 300SD Turbo Diesel Custom (235,500 mi on driveline.) - On Road!!

www.icsrepair.com

Precisely. If you overheat the fluid, all bets are off.

If you brake torque it for three seconds every 15 minutes, and drive it in the interim, the fluid will easily cool back to normal operating temperature.

My read of Adam's question is that he is not going to do it every 60 seconds for the remainder of the day.

Many people do towing with automatic transmissions. This puts significant additional torque through the transmission for extended periods of time. Some people have HD transmission coolers. Some don't.

I pulled a horse trailer (7000 lb.) with my Dodge van, 318 with a 903 transmission. It's a very light duty setup. No extra transmission cooling. I took it very easy. Tried to keep it in third gear as much as possible, even if it meant going 45 mph, because I knew that second would cause significant increases in transmission temperatures. It survived the trip without burning the fluid. This tells me that the transmission has significant capability above the normal requirement to push only the vehicle.

Three seconds of brake torque is nothing. You can do it five times a day for the next five years and the transmission won't even know it.

Brian....when you stage a car you don't let it idle...you hold the brakes...usually with line locks and rev right up to the converters stall speed and launch a feww milliseconds before you anticipate green to account for reactin time.

now that is exactly what holding your brake and hitting the gas in an attempt to build boost before pulling out is doing....EXACTLY.

The trans is not designed for that....take a read of the FSM on measuring boost...it specificly tells you to not do if for more than a moment. Becasue thats what you are doing to do that while stopped.

is a brief powerbraking going to kill it right away....likely not but its going to shorten its life a bit.

and the process is whats known as powerbraking.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

BHD is on the right track hear. Yes, if all that happened was a nice even torque is transferred down the driveline, then no damage would be done, BUT, go one rpm past the holding point of the clutches in the tranny, (and on an old tranny, who knows what that is....) and slippage will occur = damage.

Not worth the risk if you ask me, unless it is the only way to get out and avoid a wreck.

__________________
-Matt

EPA Section 609 Certified MVAC Technician
-----------------
Oil Burner Kartel Member #10

Ahh the smell of Diesel Fuel, it's like coffee in the morning!

My Car:

1982 300SD Turbo Diesel (231,500 miles!) RIP

1984 300SD Turbo Diesel Custom (235,500 mi on driveline.) - On Road!!

www.icsrepair.com

Exactly. That is what is happening.

And the transmission will not be harmed one bit by the process, provided that you don't hold it for an extended period. Three seconds is not sufficient to raise the temperature of the fluid. Nothing else can harm the transmission in this scenario, because nothing is moving within the transmission.

If you believe otherwise, kindly explain, in detail, what components within the transmission will be harmed by powerbraking. The torque through the transmission is probably less than full engine output torque, because the stalled transmission probably won't allow the engine to reach the the rpm where it puts out maximum torque (2400 typically for the diesel).

If the clutches can't handle the engine output torque in a stalled condition (estimated rpm of 1800 or so), how are they going to handle the engine output torque at maximum engine torque (2400 rpm)?

Every time you did a 0-60 run, the clutches would slip.

If you really want to discuss transmission wear, we should talk about doing multiple 0-60 times in sequence. The three second stalled condition is meaningless when you compare it to this abuse.

Hydraulic pressures rise...heat is generated in a real hurry...and you are assuming that he is not creeping forward at all. Even a few inches or feet. Those clutch packs are doing something as they are engaged and under a load...that load is transfered to every part of the driveline... seals and gaskets are under stress etc....

Like I said...its not like he is drop shifting it......that is an act the begs for a *****slapping....but its not going to help it last 300K miles either.

He is far better off adjusting his alda and shifting to low and making sure his kickdown switch is working......

That will make a far bigger difference pulling out than powerbraking in drive where its more likely it will leave in 2nd than do a first gear start....

and with that I am off to sleep......

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Agreed. I am assuming that the vehicle remains stationary. What are the clutch packs doing? They are simply transferring load to the rear wheels which is cancelled by the brakes. Yes, the entire transmission is under stress, but, there is no wear. Seals and gaskets.........yes........the increased pressure might have an effect, but, remember, three seconds isn't much time for any damage to occur.

Drop shifting is a completely different issue. That will kill the trans in short order. As for going 300K, I can't say. I suppose that the additional stress on the seals and gaskets can't be considered preferable if you want to go 300K with it, but, I have no data.

Why would it leave in second? There is no governor pressure to offset the high throttle pressure?

If he is looking for minimum times, getting the turbo spooled in advance of the launch is going to have more effect than the ALDA adjustment. But, to spool the turbo properly will require far more than three seconds. So, in such a scenario, I agree that it should be avoided, if at all possible.

That is exactly right! Does anyone remember the poor guy who started this thread?

Really, if you have traffic that bad, you need to get something with a V8 gasser in it.....

Just my $.02

__________________
-Matt

EPA Section 609 Certified MVAC Technician
-----------------
Oil Burner Kartel Member #10

Ahh the smell of Diesel Fuel, it's like coffee in the morning!

My Car:

1982 300SD Turbo Diesel (231,500 miles!) RIP

1984 300SD Turbo Diesel Custom (235,500 mi on driveline.) - On Road!!

www.icsrepair.com

i never found "torquing up " a benz resulted in a faster get away than just punching the throttle when i want to go.

so i dont do it any more. obviously it will increase wear and tear.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The turbo does not spool, the RPMs are just closer to the turbo range. It does improve time for me by probably 2 seconds 0-60. Yes driving around here in some areas is tough when people try to do 60 in a 40mph zone and the cops do nothing about it.

__________________
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

Brian....from personal observation neither of my cars will do a 1st gear start on level ground consistantly from drive...or downhill...however shifting to low they both do it everytime...and as a result spools and leaves quicker....far quicker..

A 1 gear start is partially dependent on the load....I would venture many cars have the linkage misadjusted...the alda misadjusted and the kickdown switch not even working. My cars both literaly jump off the line when I pull out from a stop..never underestimate what a properly adjsuted car can do. And if it is the powerbraking issue...would not even be considered...

And overly tight linkage will not contact the kickdown switch...an overly loose one with not give max fuel at IP..

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

I never had an issue with a first gear start with either the W123 or the W126. They always started in first gear. Now, on a downhill start, with part throttle, second gear would happen PDQ, but never right from a standstill.

You don't need the kickdown switch to perform a first gear start. However, I do believe that the switch will hold first gear far longer than it would without the switch closed.

pulling out uphill mine will do it reasonible reliably (first gear launch) but maybe 1/2 the time on level...but dropping to low I guarantee it..

I think he needs to be certain his is properly adjusted. If any other members are in his neck of the woods for compairisons sake.

My W116 pulling out like that from a side road full acceleration will get tire nearly every time in dry roads...and wet roads it will spin out...very quickly.

and I Have 225/60-15 Bridgestone Turanzas on it. Not the skinny stock size tires.

If its real sluggish he has issues that need adressed.

Maybe he needs to drive a 240D........ That gives you a fresh concept of the term sluggish.

__________________
Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
---------------------
Section 609 MVAC Certified
---------------------
"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

So, what exactly happens on level ground? It actually starts in second? Or does it start in first and shift to second way too early?

If it's the latter condition, you can adjust the cable to delay the shifts a bit.