Allison Transmission Questions

[AllisonMan]

Allison Transmission Questions

icrman,
Is there a reason you want to know this? LOL. In the valve body you have trimmer valves (which has to do with how soft or firm you want shifts), relay valves (2) shift valves and hold reg valves. If you your question easier. It would be very difficult for me to explain without the diagrams here or there to explain and really, maybe its just me because I know other mechanics that use these hydralic shematics, but I rarely need to. Sorry if I cannot explain maybe if you asked a general question on your operation, I can answer those much better. Thank you though for the question and have a wonderful holiday!

 

[AllisonMan]

Allison Transmission Questions

hfletcher, and also anyone else here take notice,and especially icrman
I do not know of icrmans qualifications with Allison transmission. It sounds like he likes the Allison, but I question his answers. I have now 28 years of nothing but Allison associated work so please beware of his answers, as I do not agree with a few of them. I also do not appreciate him answering my questions because he may give false answers. Please icrman, post your own question and answer area and go ahead and answer them but please stay out of mine. Sorry folks if I sound harsh, I do this on my own time at home at night and enjoy answering questions, but when someone comes on and gives the answers he is giving, granted he sounds like a very intelligent man, it just upsets me. so I am done for the evening. I will try to get the rest of your questions answered this weekend. Happy holidays to all!

 

[AllisonMan]

Allison Transmission Questions

srxer,
No damageshould have happened due to an exhaust brake installed, its just you will not have holdback and may have false sense of braking because you think it will work as specified. The AT is a great transmission it just lacks holdback, so enjoy it if the price is right! I do get complaints from motorhomers honestly that really do wish they had one of Allisons bigger transmissions with the lockup feature, but like I said, it works good. School buses are equiped with a lot of AT545s in them, or at least ones 3 yearsold and older. Happy Holidays!

 

[AllisonMan]

Allison Transmission Questions

Richmeister,
First try hitting your mode button. A light will come on on your shifter letting you know it is on. This may fix your problem, if not, this is a common complaint when using cruise control especially on a hill because your throttle is usually at 80% or higher when on, then drop off completly which doesn't help how the transmission shifts because you usually when driving without cruise, do not drive the throttle this way. I wouldnt be concerned but let your distributor know when you have the next service so they can check out for you on their test drive. Thanks and happy holidays!

 

[AllisonMan]

Allison Transmission Questions

RobertG,
Rule of thumb is, what gear you go uphill in, select that gear to go downhill. Please use your jakes thats why they are there. If you want to go slower downhill, slow down to around 1300-1400 rpm and then downshift to the next lowergear and the same if you want to go faster, just select next higher gear while driving down the road. Let me know if you like! Happy Holidays!

 

[AllisonMan]

Allison Transmission Questions

hfletcher,
I do think the MT643 is overkill and prob would not be a good combo. We are in the process of coming up with a marriage for Dodge truck owners, to re-gear using the Allison LCT series transmission which has lockup and replaced the Allison AT545. The holdup is we are asking customers if they are willing to shell out the approx 8000 dollars to do a conversian. So far the answer has been an overwhelming yes and that is why we are researching further. By we i mean the company I work for, not Allison corp themseolves. I will post if any more info is available. Thanks and happy holidays!

 

[AllisonMan]

Allison Transmission Questions

buffalobilly,
We usually have to machine our own part when this happens. It is a Safari part and I have heard they are not to responsive to customers asking for the pin. Make sure you have the VIN and try calling their parts department and tell them you need the Allison TPS/Throttle lever pin. Good luck and have a happy holiday!

 

[hfletcher]

Allison Transmission Questions

Happy holidays, AllisonMan! Thank you for your reply. I was hoping you would reply despite the fact icrman had. I respect your opinion that the MT643 is overkill but allow me to make two points which might mitigate this. First, the fueling of my Cummins has been turned up considerably and is usable as I also have an aftermarket twin turbo setup, enlarged intake and exhaust. Thus, the torque of the engine is approximately 800 ft.lbs. which exceeds the 670 ft.lb. torque rating of the MT643. Secondly, I already own the rebuilt MTB643 and SAE2 bellhousing. I hate to think this must become wasted funds. Therefore, I'd still like to use it IF it does not significantly demise fuel economy and/or engine torque/horsepower. That is why I've asked specifically for your professional evaluation of those two aspects. When you say "overkill" it is not clear to me whether you mean the tranny is simply too heavy or large for a one ton pickup, or whether you mean it is too massive for the Cummins 6bt to rotate efficiently. I understand this 700 pound trans will put me very near my front axel limit, and that I must either raise the body two inches or modify the tunnel to accomodate the SAE2 bellhousing etc. Thanks for your patience. HFletcher

 

[sepisllib]

Allison Transmission Questions

Just my 2 cents worth on this thread.

To begin with --- this thread was the initiative of "Allison Man" - and his alone.

For "ANYONE" to butt in and start offering their opinions and other topics of discussion is JUST PLAIN RUDE!

Please --- respect the man. He is wonderful enough to provide some of us poor souls informaiton that helps us understand our issues and problems.

Please respect him and refrain from posting - entertaining - or otherwise trying to butt into his thread.

There is PLENTY - of opportunity to start your own thread.

Just MHO - hope this does not offend anyone - but respect is due.

Plainly put.

Merry Christmas - Happy New Year

To "Everyone"

God Bless

Bill & Judy

 

[icrman]

Allison Transmission Questions

Thank you Allison man, I did finally get to look at a circuit diagram.
I just wanted to make sure they did what I thought they did.
I guess I need to give in a get a decent Allison manual.

 

[brushycreekranch]

Allison Transmission Questions

I have a 2002 GMC Crewcab One Ton 4x4 with a Duramax in it. I pull a 28 ft Aluminum horse trailer that has a 14' custom living quarter in the front. Usually the weigh runs around 10K loaded. Last April, I had to replace the Tranmission Fluid Switch after an incident where I started the truck, pushed the Tow/haul button and the truck would only pull off in 3rd gear. Onstar read the code as 0700 as did the dealership. They replaced the swith and less than 8K miles later the same thing happened! The truck appeared to only have 3rd gear with no reverse. So while my friends and I were trying to figure out how to pull the truck and trailer backwards with the tractor, I cut the truck off. It was decided that I should try to pull forward a little to more to straighten up the rig. The problem had vanished and all gears were working normally. Go figure. I drove it home, called the dealership and took it in the next day. They pulled the dsame code 0700 and said the switch needed replacing AGAIN but would not be covered under any warranty since the truck had been over 12K miles since the switch had been replaced. I needed the truck the next week and could not take the chance it would not be ready. Well, that was over 2K miles ago and no more problems have occured. The tranny shifts great. So my questions are:
1) what caused thatswitch to default to 3rd gear?
2) why would it reset after turning the truck off and then not be a problem?
3) could it be that the tranny fluid was too cold?
4) could it be that I pushed the Tow?Haul button too soon after start up?
5) should I push the Tow/ haul after I have pulled off and not before?
6)since both times it was setting under the shed, was not quite level, and had not been driven in several weeks, could the tranny fluid be settling or gelling?
7) should I request another fluid change even though it just had it done at 15K miles ago?
8) Do you think it could be a fluid problem and not a fluid switch problem?

thanks in advance
Mindy

 

[icrman]

Allison Transmission Questions

Well I didn't see all those posts yesterday, about me butting in on this discussion. I thought all these public forums, were for everyone to be able to write in, and offer some help if they can. This is the first time I have ever been chastised for trying to offer help and extra ideas. I didn't see anything, anywhere that said this disscussion was off limits.
Allisonman is a great help here, and I don't want to make an enemy. But I also have some years of Automatic Transmission experience, though very little on the "Newer Allisons", I have years of heavy equipment, truck, Diesel and gas engine, some aircraft engine, experience. Plus many many years of Machinist experience. So I do know a little bit about mechanics. I also hold an FCC License that atests to my electronics back ground. I do respect the man, but I don't appreciate being chastised for what appears as stepping on someones turf. That is very childish. Sorry I upsetted anyone.

 

[sepisllib]

Allison Transmission Questions

icrman.

I do not mean to demean you or anyone else on this forum.

What I am trying to say is this:

This thread was initially started my AllisonMan as a means of helping anyone and everyone that could benefit from his knowledge and expertise. It would not be right to butt in to his thread and begin offering the same type of input or answers as he initially started.

I would encourage you - very much so - to establish your own thread for this purpose. From your last post it appears you have a wide range of knowledge and experience. Your answers could be a big help for persons in need just as much as AllisonMan's.

It would be a really neat thing for 2 or more of you guys out that giving you knowledge.

Hope you had a Merry Christmas and Happy New Year to you and yours.

God Bless

Bill & Judy

 

[transrand]

Allison Transmission Questions

icrman,
I was also told to get off of the forum. I have many years experience with Allison transmission, but unless you agree with Allisonman 100% there is know room for you on this forum. He is very wise with his answers but not everyone is right all of the time. I don't have as many years experience, but I have proven senior mechanics in our shop wrong. That being said, yes trimmer valves are somewhat like accumulators.

 

[sepisllib]

Allison Transmission Questions

No one! NO ONE!

Is telling anyone to get off this forum.

You have every right to be here as much as anyone - period.

Right is right - wrong is wrong.

In my humble opinion - wrong is when someone tries to horn in on someone elses work - which is exactly what was going on in this thread. AllisonMan started this thread for the sole purpose of trying to help everyone out there with their questions and problems.

AllisonMan is the Author - not you - not me - not the moderator.

If you choose to set up a thread for the purpose of assisting everyone that may need your help in your chosen field - everyone will recognize and welcome your help. BUT - for ANYONE to but into YOUR thread offering advise that way - is just plain RUDE. I would be one of the first to point this out on YOUR site as well.

Offend anyone - absolutely not. This is not about offending anyone but in truth what you are doing - by posting on AllisonMan's thread is offending him.

AllisonMan - Please continue to be there on your thread for what you are doing - it is more than welcome.

icrman - Please - set up your own thread for the same thing and you certainly provide welcome answers to questions of many.

Hfletcher - Likewise - it would be really neat if you guys could outline and clearly define your expertise and thus the readers could select what is most appropriate to them.

God Bless each of you.

Bill & Judy

 

[hfletcher]

Allison Transmission Questions

sepisllib, I don't understand why you are asking me to spell out my expertise. I am merely a question-asker on this forum, trying to avoid mistakes and borrow from Allisonman's expertise. Henry

 

[Robert G]

Allison Transmission Questions

Thanks. Did a 1000 mile test drive to see if everything works. Trans works fine. I think I will keep the Dextron 2 in the trans. Why change if all works well and I do not mind having it changed when needed.
Thanks
RobertG

 

[sepisllib]

Allison Transmission Questions

That was a typo - it should have been directed to transrand - instead of you (hfletcher).

Sorry - didn't mean that mistake.

Bill

 

[icrman]

Allison Transmission Questions

transrand, I thank you.

Setting up another thread, seems a bit redundant. This one is Called Allison Transmissions.
People looking for information shouldn't have to hunt all over the place. Transrand answered my question. It was ignored in my first post. Allisonman takes a whole week or so to come here to answer questions. And besides just like going to see a Doctor, don't you like a second opinion?
Okay I have a question or two. In the Allison transmission electronic shift controller "box" what actually operates the shift solenoids? Is it a transistor? If so what kind is it? And how is it biased? Also what is the voltage and power required to operate the shift solenoids? What kind of processor is used in the controller? Motorola??
I would like to know the material that the planet carriers are made from, and if it is heat treated. Is it specific to a certain model or series that they would use different materials for the carriers or different heat treats? What do they Rockwell at?
How about the clutches, are they paper? Or something else? I would really like the answers, because I don't know the newer transmissions at all.

 

[00fxds]

Allison Transmission Questions

Allisonman: You responded to Srxer regarding the use of an exhaust brake with the AT545 saying, " No damage should have happened due to an exhaust brake installed, its just you will not have holdback ". Do you mean there would be no holdback or just not as much holdback as a lockup clutch would provide? Can I assume that I could get some retarding capability with my AT542 and an exhaust brake, as long as I monitored the fluid temperature carefully and provided addition cooling when needed? I recall during high school driver training in the sixties that we were taught to downshift the automatics on downhill sections, and that was before the lockups were invented. This option appeals to me since my rig doesn't have the space for the larger transmissions with lockup and would be less expensive that trying to add a retarder to the transmission. I would appreciate hearing from anyone else with any experience related to this. Thanks, Roger.