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#46
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The flare of thermal overload is a focused event = damage done, next event please. The focus is clutch packs, secondary effect = cooked fluid. I know Adam very well, he is adding a little (= small) extra wear, each time he does this; but he will be well out of college before the wear shows, when he gets a (rusty) winter beater it will last even longer. If the fluid is at operating temperature, brake torque causes a momentary flare of thermal overload focused in the clutch packs, this contributes to premature wear of clutch packs and fluid. The main factor is how long you brake torque and how often. I see people set at stop lights applying brake torque 180 seconds or longer = goodbye transmission. I want many hundreds of thousands of miles from my transmission + I am too cheap and lazy to enjoy changing transmissions any sooner than I am forced to. Hot torture test trips = #1. http://members.cox.net/mkpl/bakergr/bakergrade.html #2. http://www.gbcnet.com/ushighways/US99/US99g_contents.html #3. http://motortrend.com/roadtests/suv/112_9911_suvs_mercedes/ #4. http://www.automobilemag.com/reviews/sedans/0502_mercedes_benz_e500_four_seasons/index1.html #5. http://www.gbr.death-valley.us/oddsends/testmules.html #6. http://www.autoweek.com/news.cms?newsId=103021 The idea is to put them through hell, find the limits, alter as needed to meet five year 100,000 mile warranty, then produce and sell them... |
#47
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I saw a car on ebay a long time ago in which the mechanic had "adjusted the idle" to 1100 rpm He claimed it "significantly cut down the take-off acceleration times while using negligeble additional fuel." I'd think this would also be very bad for the tranny wouldn't it? Thats over 350 rpm above the max factory spec...! Sitting at a light idling that high would create a ton of heat/strain in the torque convertor....not to mention the additional stresses brought on the the brisk accelerations that follow that. He had so much good stuff to say about the car, but wouldn't say why he was selling...
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-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
#48
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either
he had it set high to mask a problem or he couldnt figure out how to make it lower...
betcha. 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. |
#49
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Can you kindly explain, in detail, how this temperature increase would cause a thermal overload in the clutch packs? Please make the assumption that the transmission is in good condition and the clutch packs won't slip due to the applied torque. It is not a fair argument to state that the clutch packs will slip under a brake torque event. If so, then the transmission is on the way out anyway. If 10 degrees would cause a thermal overload, then towing a vehicle with a trailer, for 500 miles, would be a guaranteed killer of the transmission. The trailer certainly causes the transmission to operate 10 degrees (or more) warmer for the entire length of the trip. So, if you are convinced that the three second brake torque can provide a thermal overload to the clutch pack, you will have to reconcile the fact that most transmissions can accommodate towing a trailer for an unlimited distance, provided that the driver doesn't demand maximum (or near maximum) power for an extented time in any gear where lockup is not present. I, too, wish to go a long distance with the transmission and am not an advocate of brake torque. But, as an engineer, I don't see anyone providing specific facts that prove it to be damaging to the transmission, provided that the brake torque event is limited to five seconds or less. |
#50
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Interesting thread.
I don't see how short brake-torquing before takeoff adds more heat load than the a pedal-on-the-carpet takeoff applying full engine torque. In both cases, the torque converter will experience maximum slip. Anytime the TC slips, whether at idle or the normal slip at cruising speed, the 'wasted' torque energy is converted into heating of the fluid. This wasted energy can also be measured as reduced mpg. Locking TCs eliminate this slip at cruising speed to increase efficiency. A side benefit is a slightly reduced heat load. I agree with Brian that the planetary gear clutch packs should not be damaged simply by torquing. Elevated fluid temperature, whether from the additional slip imposed by towing a trailer, running hard uphill or at high speed into a headwind, or insufficient cooling capacity, will accelerate deterioration of clutch material. Heavy 'rocking' to extricate the vehicle from snow will greatly increase the heat input from slip, and should not be done for long periods Shifting during application of full engine torque, such as 'WFO' acceleration probably causes the most mechanical wear on the clutches. To soften the shift, they are expected to slip a bit for a short period, and friction material is abraded during this clutch slipping. My $0.02 to this discussion. Best Regards, Jim |
#51
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#52
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__________________
-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
#53
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i swear
that loading the torque converter does nothing in a benz for performance.
i am going to go test it with a stop watch. 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. |
#54
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I would think it might make the "initial movement" from a standstill a slight bit faster, but the amount is so small that it'd not be worth the potential damage.....
I've put some very heavy towing loads on my car before, like pulling our 83 for eight miles to get it home when its alternator seized up....I was going about 18-20mph in 1st gear.....the weird thing is how effortlessly it still got up to speed, it lugged the other car along very easily! Running 3200-3400rpm for 45 minutes or so in 1st gear with a 3900lb towing load doesn't get very good mileage though, I think I figured it out to below 10mpg or something when I filled it after that. It sounded just like a tractor doing that, just rolling along at 3000+ rpm Tranny had no issues doing that however, and the temp gauge stayed right on 85 the whole time....
__________________
-diesel is not just a fuel, its a way of life- '15 GLK250 Bluetec 118k - mine - (OC-123,800) '17 Metris(VITO!) - 37k - wifes (OC-41k) '09 Sprinter 3500 Winnebago View - 62k (OC - 67k) '13 ML350 Bluetec - 95k - dad's (OC-98k) '01 SL500 - 103k(km) - dad's (OC-110,000km) '16 E400 4matic Sedan - 148k - Brothers (OC-155k) |
#55
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Answer: RE: transmission temperature
TRANSMISSION FAILURE/TEMPERATURE CHART
http://www.txchange.com/heatchrt.htm 1995 Mustang GT; but the theory is close enough. Installing a Transmission Temperature Gauge http://neptune.spacebears.com/cars/stories/trgauge.html Tech Articles Keeping Track of Trans Temps By Ken Brubaker Photography: Ken Brubaker The idea that what you don't know can't hurt you is flat wrong, especially when it comes to automatic transmissions. Just because you don't know that it's running hot doesn't mean that it won't eventually fail and leave you stranded. http://www.fourwheeler.com/techarticles/129_0311_trans/ Automatic Transmission and Transaxle, Page 3 of 3 http://www.procarcare.com/icarumba/resourcecenter/encyclopedia/icar_resourcecenter_encyclopedia_autotrans3.asp Report on installation of a Hayden transmission cooler By: Phill Vanderschagen http://www.dieselpage.com/art0898hy.htm What Your Dash Isn't Telling You http://www.thecarconnection.com/index.asp?article=6244&sid=277&n=158 |
#56
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Nice set of links.
But, what's the relevance to this discussion? Everybody knows that significantly elevated transmission temperatures will shorten the life of the transmission. Where is the graph that shows what three seconds of brake torque will do to the fluid temperature? If you can show that this will elevate the fluid by 25°F., then, you have a valid argument that the fluid will be harmed by the practice. |
#57
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What if the 3 seconds of brake torque would result in excessive wheelspin, wouldn't that harm the transmission?
__________________
1985 CA 300D Turbo , 213K mi |
#58
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I am still kinda curious to do my pen and paper idea. Would just be interesting to see how much the motor mounts have to take on the average 0-60 run as comapred to power braking. It seems like with the way I drive (a lot of hard accelerating) that I would have already smoked my motor mounts/other stuff if it was true that the stresses were equal to those of power braking... What effect does power being delivered out the wheels and causing acceleration have on the "precieved torque" of the engine/transmission sitting on its mounts? Its been so long since physics (my prof. sucked) that I am a bit rusty. Anyone care to comment? |
#59
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I wonder how many people who frequently power brake their auto transmissions actually have a trans last to 100k much less 300k miles?
I bet few live to see 100k with that abuse... Most of them go around blaming the manufacturer for building junk.....and not the loose nut behind the wheel.
__________________
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 |
#60
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wait
a minute...you say you can get wheel spin in a 300cd by torque loading it?
you on dirt or snow? 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. |
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