Allison MT644 for an 871

Fredward · January 24, 2014, 09:14:53 AM

I am thinking of pulling out my 8V71 and changing from the spicer to an automatic in my MC-5. I've looked around on the web for a MT644 and they seem to be available. Should have done it five years ago when I put in the new clutch. ......oh well........I keep thinking of changing busses, but we still have the -5 and the engine is easy to pull out so I know kind of what I'm getting in to.

I know I need the shifter and cable; and a flex plate, drive shaft and cooler. What do I need to attach the transmission to the engine? Can I keep my flywheel? I'd go with a used tranny and have it dyno'd before installing.

Where should I look for these items? What are the gotchas that I haven't thought of? Do I need to cut the frame to make it fit?

I guess I could replace the whole thing with a 6V71/740 combo but not sure I want to spend that much $$$ and then I've got two unknown components.

Fred

Fred

luvrbus · January 24, 2014, 09:34:19 AM

Fred, you are going to need a drop down to go from the SAE 1 bellhousing to the SAE 2 or change the bellhousing you will need the 15/16th spacer
Bobby or Kim at Global Transmission in Tuscon Az will have the parts needed give them a call they will tell you the flex plate replaces the flywheel the starter ring gear is on it one for a 740 will not work for a 644 forgot to post their number 1-888-395-1392

good luck

Don Fairchild · January 24, 2014, 12:00:21 PM

Fred, I did that to lingas bus some time back and got most of the parts from AZ transmission. If you decide to change to a 740 I would recommend a 6V92TA not a 6v71. I may have a flywheel and spacer ring.

Don

TomC · January 24, 2014, 01:46:49 PM

Using the MT644 with the 8V-71, you're up near the capacity of that transmission-and you still only have 800lb/ft torque that is affected by altitude. I wouldn't fool with the 8V-71. Find a bus or trash truck with a 6V-92TA and HT740. You'll have an engine that can easily put out 350hp and 1,000lb/ft torque and a big transmission that's barely working behind the 6V-92TA. You'll have a real hot rod. Good Luck, TomC

Lin · January 24, 2014, 04:07:22 PM

Fred, As Don mentioned, he did that job for me. I am very happy with the Allison. We used an MT-647 though. It is supposed to be a little stronger than the 644, but I really don't know that. Anyway, I would take a serious look at Tom's suggestion. There have been times when climbing mountains that I have thought the 6V92 would have been worth it. Also, what you start pricing the various connecting parts to put the 644/647 onto the 8V71, you will find that they may go a good deal of the way toward buying a 6V92/HT740 take out.

The shift control for the 644, by the way, is different than the one for the 740. You might not think it, but it does make a difference. Not only that, but the shift lever that is mounted on the transmission is also different than the 740. The 647 that we got from Az Transmission had the wrong one on it. The attachment hole position I think is supposed to be shorter. That small difference in its arc hinders it from shifting correctly. I had to re drill the one I had. An engineer from the shifter company figured out the measurement for me. It was very hard steel, and I think I more burned through it than cut!

luvrbus · January 24, 2014, 04:16:33 PM

AZ Transmission and Global are the same outfit fwiw

Fredward · January 27, 2014, 05:12:35 AM

Ok thanks guys. And yes I meant 692T/740. If I found a good one I'd consider it although I'm not sure I'd have enough height for the turbo. Might have to move it. Do you know would a 692T out of a newer bus slide right in where the 871 came out? I mean rail spacing.

I know the 871 -644 combo is a bit much for that tranny but I'm just looking at it as a stop gap to improve drive ability. The bus is fairly light, we drive on flat land 99% of the time and we don't pull a heavy toad very often. Usually a light trailer.

I've got an MC9 stored here for sale. I'll take some measurements from that engine for comparison. It's a 692T.

TomC · January 27, 2014, 09:45:21 AM

You would have to make a custom turbo mount for the 6V92TA. But-that's relatively easy-only need a pressure oil feed to the turbo and the oil return line to the oil pan. Can mount the turbo where it is convenient. The performance difference will be quite noticeable. Good Luck, TomC

RJ · January 27, 2014, 10:26:28 AM

Fred -

YTS, the transportation system in Yosemite National Park, had a couple of MC-5Cs that they swapped out the 6V71/740 for a 6V92TA/740 powerpack.

They had to move the turbo, as well as swap out the radiators for ones with thicker cores. The turbo was relocated to the driver's side of the engine, mounted with custom brackets.

The engines were set up for 350 hp, which worked wonderfully at Yosemite's 4,000 foot elevation.

The 5Cs were ex-Saudi buses with the double roof, but not the models with the transit doors front and middle, they just had the single sedan door. Somewhat rare, actually.

Last I heard they'd been traded in to ABC for some Van Drools, many of the operator staff were really sad to see them go. Wish I knew what ABC did with them - probably scrapped by now, sadly.

So, yes, the 6V92T/740 combo works VERY well in an MC-5, really enhances the coach.

FWIW & HTH. . .

Fredward · January 27, 2014, 12:57:15 PM

RJ - when was that trade would you guess? We are only 60 miles from ABC Minnesota location.

Clifford; educate me - is the 8V71 SAE 1 and the MT644 SAE 2? I emailed the boys at Global and I'll try calling them too.

Fred

Ed Hackenbruch · January 27, 2014, 02:37:51 PM

The PO put a 644 in my 5A 164,000 miles ago and it has been just fine for us.

luvrbus · January 27, 2014, 03:08:12 PM

The 644 was used in the Eagle 05 a 40 ft heaver bus than the MCI 5 with the same drop box Eagle never installed the 740 till about the end run the79 -80 models of the 05's then it was a option you still see the model 10 with a 8v71 and 644 running today

I have a friend with a model 10 and 644 and it's never had a problem in the 12 years he has owned the bus only thing we done was change the modulator when we changed it over to a air throttle fwiw

RJ · January 27, 2014, 09:49:43 PM

Quote from: Fredward on January 27, 2014, 12:57:15 PM
RJ - when was that trade would you guess? We are only 60 miles from ABC Minnesota location.

Fred -

IIRC, it was about 5-7 years ago, and they went to ABC's facility in CA.

Useless trivia: Sometimes the YTS shop would pull all the side windows on one of them and then use it for the Valley Floor tours during summers, reinstalled for the other three seasons.

FWIW & HTH. . .

Fredward · January 30, 2014, 10:01:51 AM

Clifford, I talked with Bobbie yesterday. He asked a few questions and said he should be able to find everything I need and said he would get back to me today. I told him "Clifford sent me". He said he knows you well. I was impressed that he knew what an MC-5 is and didn't faint when he learned that it had an 8V71. He is going to check for a 644 take out but said he has the parts to build a 644 if necessary. Looking forward to his call later today.
Fred

Fredward · February 06, 2014, 07:56:54 PM

Well I heard back from Bobbie at AZ Transmission. He found a good runner take out and the other pieces I need like cable, shifter, etc. Not sure about the adapter we'll need. An 8V71 with four speed spicer is an SAE1 and the MT644 is SAE2. Right?
Fred