Allison Transmission ???

[thenewkid64]

Here is a question for those of you that are big into the GM stuff.

If I had the $$ to do it, what model Allison transmission would bolt up to my 454 block? And are the computers divorced from the engine systems so it can be installed as an add on to a normally aspirated motor?

This is the only part of the drive train I have not replaced and I figured if I start saving now I will have the money and the info when the time comes to do it right. Who knows if I have the info the opportunity may present itself and I will just "have to" do it.

[dinoburb]

Hi newkid64,

The Allison might be the BEST transmission currently available for the GM world but cost and availibility might be prohibitive.

An alternative would be the 4L80E transmission which is a modernized version of the TH-400. Robust and expensive. However, there are folks out there who provide connection kits to utilize the advantages of the 4L80E in an older carbureted (non-computerized) engine. (DO NOT confuse this transmission with the much less robust 4L60E!!!)

The biggest advantage is availibility. Cost would be less than the Allison but significantly higher than the TH-400. It would bolt up to the 454.

Hope this helps some.

Take care,

[59toaster]

Most GM have a single ECM that controls both Transmission and engine. The reason is they can adjust the shift points to match engine load easier.

It would be a very expensive conversion. The stand alone computer conversion for the 4l60 and 4l80 are $800. I would expect about the same for the new allison. THen there is the price of the transmission.

Now an older Alison might not be a hard swap and may be a little cheaper over all. Most front engine school busses run Allison autos and have for 10 or so years. What I don't know is if the Industrail engine has the same transmission bolt pattern as the conventional engine like the 454.

Honestly I think the better and easier alterantive would be keep the TH400 and put a Gear vendors or simular overdrive on it.

TH400 is one tought tranny. It's also not very expensive to rebuild. It can be back yard rebuilt by a good shadtree. I have rebuilt TH350's and it was much easier then I thought it was going to be. It was also a LOT cheaper then you may want to know. Parts for a complete rebuild including a reman converter is $125-150 range. I would expect the TH400 to be about the same.

I'm looking for a Overdrive for my Burb right now Same basic set up as your MH 454 TH400. Just missed one for $400 complete. Only thing I would have to do is shorten the drive shaft and I would be darn tempted to try that myself. Couse the Drive shaft shop up the road will shorten a shaft for $40 and ballance it.

[thenewkid64]

Thanks,

I know about the weakling 4L60E and I will stay away from it. I am attempting to get a one piece transmission with built in OD to help make my new motor last longer and increase my MPG. I already have sunk a bunch of $$ in the coach, if I am going to replace the transmission I might as well go with one that is built to take to abuse. If I were to bolt on a Gear Vendors it will cost 2500 or so to do . This assumes that the 3 speed I have is good. If I need to replace it too I can add at the least a another 1500. So I figure if I can get the Allison and not have a franken-transmission for about 4 K I am in an equal position but without a possible weak link in the t-400.

[59toaster]

Hook up with your local Junk yard. Let them know your looking and they can keep an eye out for wrecks with that tranny. If they have it presold they can justify paying more for a low mile total. In a year or two I would bet you could get a low mile Allison for around $800.

[Silvertwinkie]

Although I agree for this particular application a 4l80e is a better choice than the 4l60e, I have to say, I have over 75k on my 4l60e and at least half those miles have been towing a bunch of weight or drag racing. I think beyond the mechanicals in it, if it's taken care of, (and kept cool) and not driven on like it was stolen, the tranny is a good little tranny, not by any means good for a motorhome. Keep in my they also used the 4l60e trans in the 2000 Silverado. It's not a bad trans, but I will agree that the 4l80e trans is a more meaty tranny in comaprison to the 4l60e.

Eric

[thenewkid64]

Eric,

I do not speak from experience on the 4L60E but I have been told if it were not for that transmission many of the small shops would go belly up. Some of it may be the unit is being abused, or that it is marginal for the application. I would not trust it for my purposes in a MH chassis. I will agree however that with proper maintenance and proper temp control that any transmission will work well. I just want to be able to use it with normal maintenance. I already spend enough time under my cars and the MH I do not wish to add to the list by having a transmission that I would personally worry about. That is why I am looking at an Allison. I would upgrade when the time came, or I can stay with the good old T400 and at the least know I have a unit that is up to the task for another 50K miles or more.

[Pick]

Brett, these guys should be able to answer all your questions: Suncoast I hear tell they can make an Allison "Bulletproof", unlimited HP and torque ratings.

There is also a company that builds 4L80E's up for racing or other HD applications. They have a "manual" version of the 4L80E called a Quadzilla

If an Allison doesn't fit a 454, you can always go to an 8.1L crate motor.

[Silvertwinkie]

I hear ya Brett. I sure would love to install an Allision trans in my Impala!

I agree the 4l60e in a motorhome is a bit weak, and trust me, being under my cars all the time I too can very much appreciate installing once and not worrying about it.

Best of luck on the mod!

Eric

[mcharest]

I noticed a leak under my transmission. It is a 2005 30 feet land yatch with a 8.1l . I
can't find the dipstick to check the transmission oil...where does it hide?

[vintage6t]

Originally Posted by mcharest

I noticed a leak under my transmission. It is a 2005 30 feet land yatch with a 8.1l . I
can't find the dipstick to check the transmission oil...where does it hide?

Dip stick is under the hood near the top of the radiator offset a bit to the passenger side.