no it does start in second at anything less than pedal to the metal starts on level ground usually...I never feel the upshift anyway.

And tightening the cable further (rod on the W116) results in uncomfortibly high upshifts.

Both cars pull away strong off the line......maybe one night this week I will count the revs of shaft to wheel to verify that 1,000 Rpm difference at 70 mph I have between both cars....that curiously both have 3.07 stamped on the casing. Its cooler now...time to put that issue to rest.

__________________
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)
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Section 609 MVAC Certified
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"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

Something doesn't seem right. They should never start in second. You would feel the 1-2, that's for sure.

Be nice to resolve that rpm difference. Something doesn't seem right there, either.

well both cars are strong enough I agree I would notice it...but then...it still pulls away well, just not as strong...cranking the bowden cable does ease that but then I get a 4,000+ rpm upshift to second and third.......boy thats fun on wet roads let me tell you... Made a right turn one day on DAMP roads at a stop sign floored it hit second (while straight) and put the car sideways....lucky there was nobody in the oncoming lane as this was on a two lane road. Trust me that got adjusted real quick.

__________________
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 far as power braking goes...regardless of tranny wear or not (not going to touch that one )...

...if you want to see a reason to not do it excessively, open your hood and watch your engine. Put your foot on the brake firmly, and apply the accelerator. Watch the engine stress to roll over in the bay.

Obviously the motor mounts were built to take a lot but with brand new mounts on my 300SD I can get it to move a LOT. It won't matter if your tranny has 1k less miles left in it or not when your engine drops on the drivers side and takes out the oil cooler lines..

Do I power brake? Occasoinally when I really need to (steep exit driveway into quick traffic). Not sure if it is my adjusted IP or not but my engine can make boost and power while power braking...(noting the boost gauge).

I would open your hood and watch the engine. This will give you an idea of the torque/load the drive train is taking. Then you can decide for yourself how long you want to power brake for based on the observations.

Its how I learned

Brandon, would you agree that the amount of twist in the engine compartment, and resultant compression of the motor mounts is directly proportional to the torque being produced by the engine?

If so, the maximum rpm that can be attained by the engine under a power braked condition is about 1600 rpm. The engine is nowhere near it's maximum torque.

Now, if you then take the same vehicle out on a 0-60 run, with your foot on the floor, the same engine will definitely reach it's maximum torque at about 2400 rpm.

So, even though the hood is not open, and you can't see it, don't be fooled into believing that a power braking situation is more stressful than a 0-60 run.

Everybody on here does 0-60 runs without nary a care. But, a powerbrake............well.........that's somehow catastrophic.

I would agree that the engine movement is proportional to the torque output and stress on the whole system. As far as a stock engine goes, I guess they wouldn't get about 1600RPM but mine will rev well beyond that into danger zone easily. It only sticks at 1600 if I have crap fuel.

I am not saying powerbraking is hell on earth or anything of the sort and I myself even do it occasionaly. My main point was, with the rear wheels stationary and the engine making pretty decent torque (atleast in my case) its hard on the motor mounts.

Now related to the 0-60 time? Not only do you have the drive train rotating, you also have shifts in there which, although harmful for the tranny, are "gliding" into the next gear without massive shock or abruput load.

The 0-60 runs are obviously similarly harmful but with roatating mass and actauly movement of the drive train system and ACCELERATION of the automobile...the stresses are, as I would seem to observe, lesser on the motor mounts.

As far as the transmission goes, that is another story

I know that 0-60 runs are harmful to the tranny/motor mounts as well but I can make decent reason that if my engine was rolling around in there as much as it is when I power brake for 3+ seconds, my motor mounts would already be long gone. But I guess my car is odd since it will climb higher than 1600RPM when power braking.

The aforementioned statements contradict each other if we agree that maximum torque occurs at 2400 rpm, and, you can't reach that when you power brake.

Unlike power, torque is independent of rpm. For example, 100 ft-lbs of torque with the driveshaft stopped will put just as much steady state load on the motor mounts as 100 ft-lbs when the driveshaft is tuning at 2500 rpm. Although it may be counterintuitive, full load acceleration, with the engine generating maximum torque will put the maximum loads on the motor mounts. I also believe that hard shifts, with the engine generating maximum torque will result in higher dynamic loads than "power braking" from a stop. Interesting thread.

Alright but I can sit in my driveway and make 8-10psi of boost (11-11.5psi max). My car has the garret T-3 turbo......

Can it reach 2400 rpm in gear, in the driveway?

Brake torque or power-braking as you call it is bad for transmission durability.
#1. It generates massive thermal overload in the clutch pack.
#2. It cooks the transmission fluid.
#3. It takes more time than OEM design allows for, to transfer heat out of the transmission.

I work in the OEM in prototype vehicles, and brake torque is a very common failure.
#A. The engineer wants to heat the engine fast = Brake torque.
#B. Timed sprint runs on test track = Brake torque.
#C. Maximum capacity climate control testing includes Brake torque.
#D. Durability testing transmission includes Brake torque.

Burnt fluid and clutch packs is incredibly common, but the burnt unit is removed and sent to the transmission lab for analysis.
Thermal overload is enemy of all transmissions.
This is why light trucks that haul heavy trailers need large auxiliary transmission oil coolers.
Is it really worth the risk on your personal car???

Lemme go check. I know its higher than 1600...

If the brake torque is present for three seconds, kindly explain exactly how massive thermal overload can be present in the clutch pack?

Also, kindly explain how the transmission fluid can be cooked in a similarly small time period?

If the brake torque events are limited to two events per day, are you implying that the transmission cannot transfer the heat in the interim time period?

You are clearly not comparing your brutal testing of these vehicles and the results that you have garnered to a three second brake torque by Adam and the W123, are you??

Power Braking in my 300SD:
0-2 seconds 2050RPM
2-3 seconds 2150RPM
3-4 seconds 2200RPM
4+ seconds 2300RPM

It instally pops up to 2kRPM as soon as I apply the pedal.

Outside the car does smells hot after doing that. Boost came up to 9.5psi at around 2150-2200RPM and the pyro was climbing past 1000F on its way to 1100 when I left off.

I can set up a pad of paper and a pen mounted to the engine (paper on the fender) to monitor engine movement for power braking compared to 0-60 times. I myself am curious as well.

You are very close to the torque peak.

So, in the case of that engine, it is twisting the motor mounts and stressing the internal components within the transmission in an identical manner to taking it on a 0-60 run. Maximum torque, and the point of maximum stress to the driveline components will occur as the tach passes 2400 rpm. Above 2400 rpm, the torque starts to ease off slightly and the stresses on the drivetrain is less.

So, in your case, and your case only, you can cause more stress and strain to the drive train because you are able to keep the engine at maximum torque for an extended period of time (3-4 seconds).

When you do a 0-60 run, the torque peak comes and goes in less than 1 second, so the period of maximum stress is limited to less than 1 second.

Note, however, that the torque curve is reasonably flat past 2400 rpm, so the stress is still present all the way up to about 3400 rpm. It's just not peak stress anymore.