http://www.transmissioncenter.org/cu...bt_adapter.htm

 

Thats nice and all but the allisons just dont hold up. I know a person with a duramax that converted just the opposite. Allison for 48re, it was the only tranny he could find built to stand his horses. Interesting i thought.

 

who is it? Do you know him personally? Theres only one that I know of.

we are talking over 1000rwhp here. Its going to be difficult to make any transmission hold up. The allison doesnt lend itself to shifting well with over 800hp. Its the nature of a clutch-to-clutch transmission. Its not that the "allison is junk and a crap design", its just something that comes with that type of transmission.

When guys start hot rodding the cummins's with the Aisin trans they are going to run into the exact same types of problems.



that being said theres no way Id waste money on putting an allison behind a cummins. Despite what everyone says its NOT the flower and roses flawless conversion/operation everyone wants it to be.

 

Heee heee I read this two ways... first you are really trying to b helpful....then I read it like - dont do it they are junk - I wanna keep the junk a secret

 

the ally will handle 750-to 800 hp very reliable,after that it doesnt hold as well.there are people working on it and it is getting better.progress is slow but getting better.a propery built allisson in a 6000 lb truck will allow a few 10.5 passes before it needs rebuilding.the duraflite in the same truck with no changes except tranny will go 9s with ease

 

His name is buck. I think he has or had the fastest duramax in some kind of class. He has been in diesel power i think as well.

 

Im going to check again but i think all autos have clutch on clutch. I think some manuals have a clutch to clutch operation as well. My transmission has at least three or four clutches in it.

 

yes the spruills are the only ones running a dodge trans behind a duramax. I know who he is. Extended cab short bed pewter 4x4 dmax, it runs 9's. Just wanted to make sure we were talking about the same person

 

you are incorrect.

 

I am just pulling your leg! Yes that is him, why do you think that is?

 

just pulling my leg? On what issue?

why do I think they switched to a dodge trans?

because you cant make a clutch to clutch trans (be it an Aisin, allison, 6L80, etc) shift reliably and quickly that fast under that much power. Not going to happen without severe risks of tie ups.

The allison is a towing transmission designed for light/medium duty truck use. It was meant to move huge loads around efficently at stock power levels and last a million miles while doing so. (now that I said that lets hear all your "well my brothers uncles mailman has a friend who is a service writer at the local chevy dealer and they've had to fix 78 blown up allisons in the past week" stories) It is NOT a drag racing transmission and &*@#s when used as a drag racing trans. I have explained this in depth in many of my past posts.

On the contrary, the dodge automatic is not a towing transmission! No offence (and I dont think TOO many people will disagree with me) I have driven many auto CTD's and the way the 47/48re works and shifts makes me want to drive the truck off a cliff. I couldnt imagine towing huge loads every day with one. Its never in the right gear, the locking/unlocking of the converter is annoying, and the gear ratios are totally wrong as far as keeping the CTD in its proper RPM range where it makes all that stump pulling torque that we know its capable of. It was not designed for heavy towing and it certainly wasnt designed to live and work efficently behind a monster like the CTD. Its a 40 year old torque flite with an OD housing bolted on. The ratios are designed to provide light trucks and cars with good accelleration at light loads.

What does this mean? Its awesome as a drag racing trans!!! The aftermarket has been perfecting it for 30 years and the design of it (when built up with billet/strong hard parts) works well for drag racing. There are overrunning clutchs, so you can bang one gear right on top of another and its not possible for there to be a tie up, and they will shift lightning fast with no power loss/interuption between shifts. And the ratios are perfect for getting a vehicle down the 1/4 mile in the fastest time possible. In drag racing/big power applications, the allison's only saving grace/high point is that its hard parts are indeed massive and you dont need to spend $$$$$$$$$$ on billet this and billet that.

Look at the allisons ratios. They are terrible for drag racing! If you have ever drag raced a dmax with 450+ rwhp you will see what I mean. On launch, you blow through first gear before you're even at the 60 foot mark. And because the trans is 100% dependant on the TCM (trans computer) to work, it doesnteven know what just hit it when you did that 20psi boosted launch at wide open throttle. By the time it realizes "holy jeez I need to make 3 complicated precisely-timed-to-the-milisecond shifts AND lock the converter in a matter of about 4 seconds", its already too late and the trans has missed the shift and it sits in limbo there between first and second gear while the TCM fumbles around in the dark like an idiot trying to find second gear and make converter lockup happen.

the converter cant be locked in 1st gear with the allison. And the converter CANT be locked manually like the dodge guys have the luxury of doing. We are at the mercy of the TCM, and most of the time, it doesnt follow "standard procedure" and doesnt even "find time" to lock the converter until the top of 3rd gear. You just lost the race when that happends. Its probably the reason my truck traps almost 110mph (low 12's), but I have yet to run better than 12.8!!

So there, a short tid bit of info why the allison sucks for drag racing, and why the Spruill's gained something rediculous like .5 of a second JUST by changing to a dodge trans, and keeping the rest of the truck's setup identical. Its just the nature of the beast.

ben

 

Well then the ultimate should be a 48 RE with a gear splitter for towing.

 

O.K. guys, lets try to keep this thread "civil!" So far, so good, but these threads tend to "get out of hand" sometimes.

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John_P

 

Sounds like you have allison syndrome! I wasnt trying to **** you off, but it looks as though its too late. Maybe you should buy an 48re and get rid of the allison. Since you speak so highly of it. I like the way my piece of crap 48re shifts. And as long as it keeps shifting to me its the best piece of crap since the last piece of crap that i owned. I am really surprised its help up this long, i will give it credit for that. Most of my friends have already had to swith to aftermarket trannys. I just ran an 8.654 in the 1/8. Just motor and my few crappy mods.

 

O.K.,......looks like the warning didn't work. This one is done.............

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John_P