Diesel Place banner

1 - 17 of 17 Posts

·
Registered
Joined
·
1,310 Posts
Discussion Starter #1
im not most, and read on another post, but what is trans slip? how does it happen, what does it hurt?? I know my basics, but still not very automotive intelligent...thanks for the explanation guys...-Adam
 

·
Registered
Joined
·
12,262 Posts
The Torque Converter slips until it locks in second in Tow Haul or in Overdrive in regular mode ...As the clutch packs are being applied and released some slipping will occur ... All of this is accelerated with the intro of power adders ...


Additional pressure and Clutch pack capacity will keep the clutches applied under increased HP input ...


Crud but I thought I'd get the topic rolling ...





Mac
 

·
Registered
Joined
·
14,323 Posts
Adam


Picture a stack of wet clutches like in a motorcycle. We have a hydraulic spring loaded apply piston(usually aluminum) springs are there for return of the piston after apply, but also to regulate timing so they don't come on too fast (TCMs hate that). Clutches are alternately stacked (steel plate at the bottom against the apply piston) then a friction plate ( a steel plate with paper friction material on each side). A slip occurs when there is not enough pressure on the apply piston to lock the clutch stack, or there are not enough clutches in the stack to hold current torque being applyed. Low fluid or the kind of fluid you use has an effect. Clutch packs are rated at the factory to hold a certain torque application plus 10 percent. What we do with our trucks far exceeds what the factory built in for safety. Adding clutches helps alot ; example ( C3 clutch pack has 4 clutches, by adding one friction and steel, you just increased clutch holding by 25 percent). Adding pressure also helps in locking clutches better, but touchy in the Allison because of back fill. (we will do that another time). You will feel a slip when the engine rpm goes up and the vehichle does not respond accordingly. Slips start as little flares( slight rpm zip and bump before a shift). The zip starts to get worse and becomes a slide, then becomes a nuetral condition after shift. Sorry if i took too long, hope this helps.


mike
 

·
Registered
Joined
·
520 Posts
MikeL,


I now have a better understanding of how automatics work.


Any chance you could include some pics and/or diagrams?


Thank you and when is the next lesson?


Blake
 

·
Registered
Joined
·
1,310 Posts
Discussion Starter #5
so when it slips, it should be fairly noticeable correct?? There will be no mistaking it??...i dont forsee me hauling any loads over....4-5K....what does slippage hurt in the short and long runs...?
 

·
Registered
Joined
·
14,323 Posts
Slip is:


Engaged clutch or band not holding torque(forward movement under power in a positive form) I just made that up for the question. The ultimate purpose is to get the engine power to the rear wheels without any loss of torque. That means the engine must never rev beyond required torque. (i do not use hp numbers here because they are meaningless). If it does, power(tq) goes down the drain. Diesels have a small window for power( parameter as we call it) and they can make monster power within this small window. If you slip the trans , which means that you basically over reved, you lost power big time.. You will notice higher rpm's and less response when this happens. I hope I didn't bore you guys. Just trying to help.


mike
 

·
Registered
Joined
·
1,310 Posts
Discussion Starter #7
I hope I didn't bore you guys. Just trying to help.

I greatly appreciate you taking the time to explain it for me...You could have easily read the post, and been like ha, what a idiot and been on your away...Im learning little by little...Thanks-Adam
 

·
Registered
Joined
·
14,323 Posts
Adam


I have learned plenty from you guys and the research you guys do on any given subject. You guys are enthusiasts as am I, and I just (maybe
) know more about transmissions than a lot of you guys? not sure about that anymore. You guys are good.
I have been taught by the best(thank God) and hang around these same guys still after 38 years, I like giving something back.


regards, mike
 

·
Registered
Joined
·
1,124 Posts
Mike,


If you can increase the torque capacity by adding more friction/steel pairs, then the next question is...


How many pairs in the Allison 1000 series can you add in any of the clutch packs with or without case modification?
 

·
Registered
Joined
·
14,323 Posts
Case cannot be modifyed fot clutch capacity. Thinner steels and frictions for C3 and C4 and cutting pressureplate thickness. ATS supplys 120" spacer for P1 planet ring gear to lift it up because clutches run out of splines.( top clutch wont catch splines) C2, you are limited because it is contained in front rotating unit ( Suncoast uses 7 frictions with pressureplate. C1, seems everyone is going to single sided plates( still contained in front rotating unit. C5 don't matter.


mike
 

·
Registered
Joined
·
1,124 Posts
That's means that the clutch packs become more heat sensitive and if one does crank them, the go quicker?


And one more Mike, what is the calculated max input torque that the 1000 series will hold with clutch mods?


Thanks for the lessons. I'm sure the big guns are soaking this all in. Boys, save your pennys for a bigger Allison.
 

·
Registered
Joined
·
139 Posts
some one asked for a picture of the clutches......this is a disassembled view of the c4 and c5 clutch packs on an allison



 

·
Registered
Joined
·
280 Posts
Have any of you transmission guys come across anyone warping the stock steels?


When the trans is modified with more clutch material via thinner steels, etc., has anyone seen warped steels in that application?
 

·
Registered
Joined
·
3,410 Posts
All transmissions slip, it don't matter if it is automatic or manual. the amount of slip determines how long it will last. The clutches are designed to slip to prevent things from breaking. It seems that anymore they make them slip more to make shifting as smooth as silk to make people happy, but at the expense of longevity.


Just my take on this subject!
 

·
Registered
Joined
·
14,323 Posts
DavesDmax


Making clutches thinner to increase capacity increases total square in apply. I prefer to machine an apply piston and keep the clutch plates as thick as possible for heat dissapation. Sometimes that cannot be done without total re-engineering of the trans. Transgo saw this with the C2 and figuered a way to increase piston apply area. ( the C2 piston is basically a three stage piston) using about 13 sq inches of apply. When the C2 piston is modifyed in the Transgo shift kit, that area is increased to 19 sq inches by restricting the two bottom bleed off holes in the piston and cross drilling piston to eliminate the function of the C2 ballance piston( there only to seal off top portion of piston apply area ). The C2 piston can still be increased to another 6 sq inches of apply, but that got too violent. There is always the argument that if you machine the clutch plates thinner they lose the ability to cool, but the argument goes the other way, more clutches to share that heat. Which is better? Thicker clutches, but you give up holding power. Better cooler, I'm doing that right now. As far as how much input tq will the Ally hold with mods; I am more concerned what it will hold at the wheels when all is said and done. Thanks for listening


mike
 

·
Registered
Joined
·
520 Posts
Thanks World Class it helps seeing how it all lays out.


Mike L you have a way with words that makes it easier for non tranny guys to understand.Thank you for sharing your expertise.


Blake
Edited by: NWDmax
 
1 - 17 of 17 Posts
Top