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Topic: Allison MTB648 Transmission Mystery (Read 786 times) previous topic - next topic

Allison MTB648 Transmission Mystery

In the latest episode of "Grand Villa Mysteries" we open on an Allison transmission for which no filter can be found, anywhere on the planet.

A local truck shop attempted to change trans fluid and service my Allison MTB648 trans more than a week ago, and the coach is still there, because: 1. Allison no longer makes the filter bearing the part number of the installed unit, and; 2. Allison sent the shop some type of conversion kit that would enable the installation of a currently-manufactured filter, but the parts don't work in the transmission in any manner whatsoever, and the project is thus stalled.

Has anyone experienced or heard of such a situation on a GV U300?

1989 Foretravel U300 Grand Villa
Build #3410

Re: Allison MTB648 Transmission Mystery

Reply #1 –
Back flush the old filter, take a pic noting the specs, and put it back together.

Re: Allison MTB648 Transmission Mystery

Reply #2 –
Quote from: Protech Racing –
Back flush the old filter, take a pic noting the specs, and put it back together.

Think he said the filter is missing.. Maybe thats why it wasnt replaced because they couldnt get one?

Re: Allison MTB648 Transmission Mystery

Reply #3 –
Mike, Thanks—I'll keep that in mind as a last-ditch solution if necessary. The shop has Allison working on this and I'm still hopeful that they will arrive at the appropriate technically correct, Allison approved solution.
1989 Foretravel U300 Grand Villa
Build #3410

Re: Allison MTB648 Transmission Mystery

Reply #4 –
Can you get us the part number that is on the old filter? Possible we could get specs on the old existing filter and then try and find something that will match the specs of the old one.  I can see if someone is getting paid and can not find something quick they will say it can not be found.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Allison MTB648 Transmission Mystery

Reply #5 –
It can be done if you are willing to do it,if there is a place on the oil pan where there is no oil pressure,like the sump,you can install
a bypass filter or a dual remote filter system,all you need is a oil pressure point and a oil return point,check out the Amsoil website
you can look at their filter systems.Have installed these on many vehicles over the years and it would work in this case.Even if you remove the pan and have a return fitting installed it would be worth it.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Allison MTB648 Transmission Mystery

Reply #6 –

Is it a spin-on or cartridge type? It could be the same filter the later 746 Allison the U300s use or the 747 the U280s use behind the Cummins. Got to be someone on the forum that knows. Don't expect a shop to know the answers, go to the company's tech service.

Have you called Allison support?  U.S. and Canada Toll Free: 877-659-6913 or Allison Transmission | Technical Support

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Allison MTB648 Transmission Mystery

Reply #7 –
Randall,
I have an externally mounted transmission filter which is the only filter I have changed on my coach.  This is the stock setup on my coach which I think should be the same as yours.  I have an MTB-648.  The brochure only mentions an external filter but the owners manual does discuss an internal filter.  I wonder if the internal filter is omitted when the OEM installs an external.  If you have an external, I'm surprised (but maybe I shouldn't be) that the service people didn't identify it.  It clearly has hose going to and from the transmission.  It's a NAPA 1268 filter,  the Foretravel manual lists the filter number as AC HD223.  The Foretravel manual has way more specific and comprehensive information than any mechanic you are going to find today at a truck shop.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Allison MTB648 Transmission Mystery

Reply #8 –
Might consider  adding the external filter in the cooler lines  and a simple screen inside  ,on the pickup.

Re: Allison MTB648 Transmission Mystery

Reply #9 –
My 647 has an external filter also, backwash the "rough" pan filter, if it was serviced early in schedule and something hasn't failed it probably filtered all of big particles from manf and intitial break in. At this point it may just be along for the ride and not even capable of filtering and retaining much smaller normal wear particles. Jmo
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake
 

Re: Allison MTB648 Transmission Mystery

Reply #10 –
I, like John above, have an external filter. Baldwin BT 230. 
The Starship- 1990 Grandvilla Unihome U300 40ft
6V92 Detroit Diesel w/ 4 spd Allison w/ retarder. Build# 3575 , Foretravel# 17895
The Shuttlecraft- 2015 Ford Explorer
Steve ( N6EKV ) & Lori ( N6JTD ) Faries  w/ Marlee our precious pup.
Patterson CA.