Does the Allison have a retarder ?

[deerhunter7]

I thought I read some place that the Allison has
a retarder. Thought it talked about a oil stream
aimed at a vanes reverse rotation when the tranny
senses you are slowing down.. :confused:

[77TransAm]

There is an output retarder available on the MD and HD transmissions. It works similar to the principles of a torque converter, except that the rotating part is splined to the output shaft and the stationary parts are cast into the rear of the trans. When fluid is applied to the retarder cavity, it slows the output down in a HURRY.

No such creation on the 1000, though; it gets grade braking instead. Retarders create massive amounts of heat in a big hurry - your truck would have a very different cooling system if it had an output retarder.

[deerhunter7]

Thanks 77TransAm , That clears the fog. Must have been reading about the MD or HD models. Must of been that HD that confused` that mass between my ears... :D

[Bobcat698]

Hmm... I was thinking of asking the same thing.

It seems when you let off the pedal a bit, it slows down in a hurry.

GS

[Jake99Z71]

77TransAm,
Could you tell us how to connect an Exhaust Brake to the Allison TCM?

[77TransAm]

I could, but it wouldn't do you any good... GM hasn't released a cal that will do anything with that input signal. smile.gif

[tpitt]

Jake99Z71,
Not sure what your talking about with the tcc. I have an exhaust brake on mine and it works fine in the tow haul mode. The tcc stays locked up in tow haul until above about 22 m.p.h. tpitt

[MountainMax]

Go see Kennedy's post under the topic "Grade Breaking" on the Duramax forum.

[Jake99Z71]

77TransAm,
Thanks, I had read a few months ago that Allison recommended intergrating the Exhaust Brake with the Allison TCM.

tpitt,
If you head over to http://www.allisontransmission.com/service/faq/
you can read how Allison recommends integration with their TCM for better braking.

[tpitt]

Jake99Z71,
Just read the Allison page. Not exactly sure what they're talking about. I've installed two of these already and have two or three more to install soon. The two I installed work fine, (in tow haul mode) one of these is my personal p/u.
I have noticed on my p/u when the transmission is cold the torque convertor wont lock up.
Anyone have the answer? Inquiring minds want to know. tpitt

[Jake99Z71]

tpitt,
You may want to read http://www.gmtcny.com/allison_lct_1000.htm this will explain why the converter is not locking up.
I have had the mentioned harsh/objectionable shift from time to time in Tow/Haul.

[tpitt]

Jake99Z71,
Interesting reading. Thank you. From where I live everything is mostly down hill for a few miles. It will engage after a couple of miles though.
I've never experienced any harsh shifting with mine, and the exhaust brake seems to work well. If you should happen to find any more information on the Allison with the exhaust brake please post it. I sell these as a side business and I definately want to know if theres going to be any problems. Thanks again, Terry

[77TransAm]

tpitt, you shouldn't run into problems installing the systems as the manufacturer recommends, you just won't be getting all the features and benefits that you would if it was integrated with the vehicle systems. With an appropriate calibration installed, the exhaust brake will only come on when all of the correct parameters allow it, and it will work better than it would on its own. For example, when the TCM allows the exhaust brake to come on it will also preselect a lower range (usually second) and keep the converter locked as it downshifts. Integration also adds some safety features; the exhaust brake will automatically be shut off if an abs event is triggered, for one. I'm sure there are other features - those are just some that I thought of to give you examples of why an integrated setup would work better.