For the stated record, I did it once every few days for no more then 3 seconds. I am not the type who has to race from stop light to stop light as fast as possible only to slam on the brakes. I usually baby the car around very leisurely. I am amazed at the input I got in this thread compared to other transmission questions I've posted.

Edit: I never have stomped it to the floor while holding the brake, so I've never hit the turbo range. I usually get it up to ~1600 rpm

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

Whunter is a Master Mechanic with a several certifications....I have worked with him on some troubles I have had before and trust his judgment. And I trust few mechanics...

__________________
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 opted not to read all five pages this is up to currently but...

It's not the smartest thing to be doing on the driveline. Heat build up, shock loads, converter ballooning, etc

You'd be VERY suprised how much load is put on a trans once the turbo spools up to full load being brake torqued if we're talking about full pedal to the floor versus part throttle. There simply isn't enough fluid (or large enough cooler) to dissipate that heat and it'll start to break down clutch material (obviously not a large amount at once), seals, steels, etc.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Sorry Brian
The torque curves you ask for would be OEM confidential data.
I am looking for an outside source that has released that type of data; but none found yet.
Some of the data is known to be public record, if someone is willing to dig into tons of court documents regarding premature automatic transmission failure litigation.

This link may be of interest to you.
Inside B&M's Torque Converter Dyno
http://www.chevyhiperformance.com/techarticles/148_0204_torq/

....and if he told you he would have to kill you.

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 discussion was limited to precisely what damage will occur to the transmission if the engine was brake torqued for 3 seconds. After the event, the transmission is allowed to cool down by driving the vehicle for at least 30 minutes until the next brake torque event will occur.

Everybody is in agreement that it's not the smartest thing to do to the driveline. Everybody is in agreement that the trans fluid will heat up a bit due to the brake torque event. Everybody is in agreement that a temperature increase of 25 degrees over an extended period of time will shorten the life of the transmission.

But, nobody has been able to provide any data to show how much the trans fluid increases in temperature during the 3 second brake torque event. And, there is no other failure mode, to my knowlege, other than significantly increased temperatures should they occur. There is no clutch slippage and no clutch wear during the event.

Without the data of temperature rise over three seconds, all the theory of transmission damage is all conjecture.

Security is not a joke in OEM land...

Well, Roy, you have clearly seen the data.

Can you provide a clue as to the temperature rise in three seconds?

All we really need to know is whether it is less than 25°F. If so, then there is not much of a case for transmission damage, by the longevity curves that you provided in the links.

Ah I see. After I read part of the way through the first page the thread seemed to go somewhat off track. It happens.

Three seconds is not even enough time to get the turbo spooled up well enough to create enough load for the heat needed to start breaking internal wear items down. I'd say around 200-220°F.

When I had my WRX, it took I'd say eight to nine seconds (that's a long time!) to get the converter really loaded up off the turbo. There would be so much load even with the brakes to the floor the vehicle would creep forward. I had an extra trans cooler on here and changed the ATF every 10K to be certain no metal filings were collecting in the pan... worked fine until I sold it around 45K mi. I only brake stalled it four times to that point as I know it's just not smart.

As you said, nothing is being applied to cause wear to the friction materials since the unit is only in 1st gear. Curious as to if the unit is heated up to a higher point of let's say 220°F, would that reduce friction life when each of the packs are applied. Perhaps if varnish is forming at that point or if the material comes off easier at a higher temperature.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Which would sorta make me think the stresses are lesser when doing 0-60 runs as compared to power braking. On paper it seems the same but we don't have transmissions failing at 100K or less like you would expect doing power brakes at every stop sign (assuming you were WOT off of each stop sign).

I've put 26k rough miles on my benz and I do not "baby it". The transmission acts flawlessly. The miles speak for themselves...

...iono.

Problem is a trans is not a living thing...it doesn't heal itself. Small ammounts of abuse collectively add up to result in a premature failure at some point.

Ever pay notice to how so many kids seen to have their cars blow up or break down so frequently...its not old or junk cars...its abuse likely 90% of the time...people who flog their cars don't see them last 500K miles on the original engine or transmission...

I don't flog my cars ..but then I don't drive them like grandpa either...I honestly doubt mune will see 500K on the original engine even though I am religious with the oilchanges and maintenance.

__________________
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

As stated before, I can not answer that question.

I have been in street rods with trans temp, doing a three second brake torque starting from 140F they could go up to 320F...

Guys,

This isn't that hard to estimate. Assuming 100 shaft HP is available for 3 seconds, that's about 71 BTU/sec being put into the converter, for a total of 212 BTU. If tranny fluid has a Cp of about 1 BTU/lb/F (like water) and we guess that there is about 2 quarts of fluid being heated (about 4 pounds) the fluid will heat up about 50 F. If my guesses are not accurate, you can adjust them. Interesting discussion.

but just how mauch tranny fluid is in contact with the effected area at any given time....a very small amount...adn that small amout will heat in very short order...

Localized heating is the issue...not the average temp of all the fluid.

__________________
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

This is just a guess, I assumed there wound be enough mixing so 2 quarts of fluid would be exposed to the heating over the time of 3 seconds. Pick whatever number you think is a appropriate and ratio the numbers.