Downshifting... Is it a killer? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-08-2003, 02:30 AM   #1
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Default Downshifting... Is it a killer?

Ok i have heard rumors that if you downshift when you go downhill to use engine compression instead of your brakes (as i do) you kill the tranny. Now does it actually kill the tranny enough to be worse than if I were to just lay on my brakes and pay for pads a lot? I downshift a bit cause i live in the hills of KY but i figure it couldnt really hurt because its what the tranny was made for just with the pressure on the other side of the gears.... Any input?
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Old 08-08-2003, 12:47 PM   #2
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Do you mean like useing the lower gears? Like putting it in D or 2 when going down hill? I didn't think it would hurt if you are going down hill. I would rather do that than burning the brakes up slowing down (brakes fading). I wish cars came equipped with jake brakes like trucks then there won't be any problems.
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Old 08-08-2003, 03:58 PM   #3
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I always thought it was bad for the tranny...... but I'm no mechanical guru...
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Old 08-08-2003, 08:59 PM   #4
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I would say that engine breaking wouldnt harm the tranny unless your RPM'* were really high. But I wouldnt trust my word until mechanical genius puts in their word.
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Old 08-08-2003, 09:23 PM   #5
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Price out a set of front brakes and rotors and compare that to a new tranny.
Not only does it harm the tranny ( high preasure) but also adds unneeded motor loading, other than a cool sound when down shifting there is no benifit.
As for diesel 'jake' brakes there is no comparison, my car has like 8.5:1 compression while my truck has over 15:1, the way the jake works is by exhaust preasure something a gaser cant handle ( back fire through the intake comes to mind?)

Just my 2 cents
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Old 08-08-2003, 10:00 PM   #6
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Quote:
Originally Posted by PontiacDad
Price out a set of front brakes and rotors and compare that to a new tranny.
Not only does it harm the tranny ( high preasure) but also adds unneeded motor loading, other than a cool sound when down shifting there is no benifit.
As for diesel 'jake' brakes there is no comparison, my car has like 8.5:1 compression while my truck has over 15:1, the way the jake works is by exhaust preasure something a gaser cant handle ( back fire through the intake comes to mind?)

Just my 2 cents
I used to drive trucks and I knew the jake brake was just an engine retarder. The sound was something I can't explain.
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Old 08-08-2003, 10:26 PM   #7
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Quote:
Originally Posted by PontiacDad
As for diesel 'jake' brakes there is no comparison, my car has like 8.5:1 compression while my truck has over 15:1, the way the jake works is by exhaust preasure something a gaser cant handle ( back fire through the intake comes to mind?)
Quote:
A Jake Brake modifies the timing on the exhaust valves so that, when braking is desired, the exhaust valves open right as the piston reaches the top of the compression stroke. The energy gathered in the compressed air is released, so the compression stroke actually provides braking power.
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Old 08-09-2003, 02:26 AM   #8
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well the owners manual suggests to downshift on hills to reduce the premature failure of the brakes
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Old 08-09-2003, 12:51 PM   #9
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Quote:
Originally Posted by [email protected]
well the owners manual suggests to downshift on hills to reduce the premature failure of the brakes
I was about to say the same thing, I remember reading the owners manual for my dads car way back ( toyota camry) and they DID recomend using a lower gear to slow down ( engine brake). Haven't read the owners manual for the bonnie yet though.
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Old 08-09-2003, 02:01 PM   #10
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in the 1990 owners manual it is on page 198 and 199. in the 1992 owners manual it is on page 170 and 171.

Devon
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