Trans for Mci 5 auto change over

[robertglines1]

Was in chat last nite and new member ask about changing transmission in his MCI 5  mid 70's pre ddec.  Would 700 be easiest and how much performance/fuel mileage would he loose? 8-V71 with 4spd manual now.  I did best to answer but feel I didn't do a good job. His engine is on shop floor now so it is decision time for him.  he is new to board and learning how to navigate it.    opinions or experiences.?  Would Jake brakes work as well with Automatic??    Bob

[luvrbus]

Bob, if he going to keep his 8v71 he has to stay with the 600 series and they are a nightmare to find all the parts to  convert over with the drop down and spacer and very are pricey from the people that have the parts.
Me IMO it would be cheaper to go with a 6v92 and a 740 been there done that lol

good luck

[Ed Hackenbruch]

 I have gotten from 6 to 8.2 mpg at different times with my 8v71 and Allison 644 tranny. My average mpg over almost 40,000 miles is 7.24    A lot will depend on how, and where, he drives it.

[viento1]

I pretty much hover around 7.5 with the same setup as Hackenbruch. The other setup was 10mpg with the stock setup. Also much slower with the auto... but...

It would take 2000 miles for any of my friends to get used to driving the stick and it scared my wife. My wife Drives the auto now and I get to rest periodically - increases our miles per day and is much more relaxing

The Jakes work perfectly with the Auto and I never never warm up my brakes it is wonderful and now I am overconfident and drive to fast...  just kidding!

The old set up with no Jakes made for a very un nerving down hill - especially inexperienced drivers do no realize how slow you have to go, how little braking reserve there is...

[TomC]

6V-92TA with the HT740 would make a great setup for the 5.  Plus you get turbocharging.  Relatively easy to find the 6V-92TA and the Allison HT740 as compared to the Allison MT644.  Good Luck, TomC

[robertglines1]

See guys  I didn't realize it had a drop box.  My lesson for the day.  Would Eric Brown's set up he took out of his Eagle work? I know it is for sale reasonable.  It was from behind a 8V71.correct?   Bob

[luvrbus]

Nope it won't work Bob too long has to be 644 four speed 645 is a five speed Eagle can use a 740 without problems as they offset the engine to the drivers side with the drop box and MCI installed theirs on a angle from the center to the drop box.

You can buy the parts from Kim at Global in Tuscon 528-295-1398 not cheap but he has parts for the change over 


good  luck

[robertglines1]

Guess all things considered : a guy with a bus with a drop box and a good working standard trans has little choice without spending a bunch of dollars. To change to any other type of transmission.  I have never had to deal with it.  The Mci 8 I had Then the prevost didn't present these problems. Sorry I didn't have the rite answers for him  hope this helped him make a decision.   bob

[bevans6]

If you go to a 6V92 in a MC5 you have to consider a few things.  First is the accessories at the back of the engine.  You have to install the laid over air compressor, the power steering pump drive and the belt drive alternator setup, if it isn't already there.  Then you have to be ready to make or substantially modify the engine cradle from the 8V setup.  you need the front at the same spot, but you have to move the rear mounts and modify the engine angle - if you just move the 8V-71 mounts forward the engine will be at the wrong angle and won't point at the drop-box.  All this is solved if you find the cradle and gearbox from a 6V71/740 equipped MC-5. obviously, but if you are starting with a 8V71 you got some finding to do...

The guys I know who have the 8V71 and 640 love it. Again the challenge is finding the kit of parts.

Brian

[Slow Rider]

New post about 600 series trans......

[luvrbus]

A 653 won't work for him too long and a deep ratio low gear manual shift for low gear transmission


good luck

[rcbeam]

I asked this a while back and never saw the answer.... What is a DROPBOX?

[Timkar]

Dropbox transfers power from driveshaft to drive axle.
see link....http://www.meritorhvs.com/MeritorHVS_Documents/mm23c.pdf
HTH...Tim