RV Trip Planning Discussions

Go Back   iRV2 Forums > POWER TRAIN GARAGE FORUMS > Allison Transmission Forum
Click Here to Login

Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Thread Tools Search this Thread Display Modes
Old 01-09-2019, 01:16 PM   #1
Junior Member
Join Date: Jan 2019
Posts: 5
Allison AT 542 Upgrade

Greetings. I'm new to the forum, but I've done a lot of research here and on other forums in regards to my desires to upgrade my transmission. Here's what I currently have: It's a 97 Newmar Kountry Star FRED with a 5.9 Cummins 12V and the Allison AT 542 transmission. It's kind of a dog, especially at the top end. It's hard to hold a steady 71-72 MPH on flat ground, much less even the slightest grade, and pulling the serious grades through Wyoming is a joke. I suspect the engine is making pretty good power, as it has a Banks Stinger kit in it, but I'm losing a lot of that power through the non-locking torque converter. I know it's also costing me fuel mileage (average 7.5 on a 5,000 mile cross-country trip). So I've come up with three possible plans:

1. Upgrade the torque converter to something with better power transfer. This would help somewhat, but I suspect that the $800 - $1000 I'd spend would be disappointing in the end.

2. Swap in an Allison MT 643. This would give me a locking torque converter and keep the installation simple, as the transmission is mechanically controlled. Still no overdrive, but I think I'd be able to hold a steady 75 MPH and maybe pick up a few MPG.

3. Swap in a 1000 or 2000 series Allison. This would be a little more complicated, because now we're dealing with electronics, but since the engine is mechanical, there's no interface with an ECM. I've read elsewhere that I could use an early (2000 or 2001) Duramax TCM and wiring harness and make the wiring really easy. This would give me overdrive, a locking torque converter, and probably a serious increase in MPG. I read somewhere that I can control it with my dash-mounted shift lever, which would be a bonus as well.

I'm not afraid of turning wrenches (I can fix or build just about anything) but the Allison transmissions are new to me, so I would appreciate any expert advice you could give me about anything I might not be thinking clearly about (bellhousing, torque converter, wiring, etc). I plan to keep this motor home for a while, so I'm willing to invest a bit of money into it, but I also don't want to break the bank (in other words, I'm kind of cheap).

Thanks for your help!


1997 Newmar Kountry Star FRED
Freightliner Chassis, Allison MT 542, Banks Stinger
NewmarKS1997 is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 01-09-2019, 06:05 PM   #2
Senior Member
Wizard's Avatar
Winnebago Owners Club
Freightliner Owners Club
Join Date: Mar 2007
Location: Home on the hill in Georgia
Posts: 2,573
My 5.9 with the MT643 still only gets 8mpg on the best days. May help you a little with pulling power. I still slow to 40 or so on any fairly steep grades. Normal interstate driving it will hold speed most of the time. I never expect to be the first one to the top of the hill

Jerry & Patsy Potter, Taz & Jake Jr.
2000 Winnebago Journey
2006 Ford Explorer 4X4
Wizard is offline   Reply With Quote
Old 01-10-2019, 10:57 AM   #3
Senior Member
Join Date: Apr 2009
Posts: 456
There have been a lot of motorhomes upgraded from the AT540/542/545 to the MT643. It's a fairly easy swap. You have to get the right adaptation hardware for the back of the engine, the same selector could probably be used, and I believe there is a slight change in driveline length. It does make a much better driving vehicle, especially for downhill braking.
As you stated, the 1K/2K swap is more complicated but you do get overdrive. The early pickup truck TCMs are usually programmed as five speeds. The transmission has the hardware in it to be a six speed but you have to be careful with driveline speeds anytime you put in an overdrive, especially if you try to go to six speeds. A complete driveline analysis should be performed. I believe you can still find the Dana Expert analysis tool free on Dana's website. Allison dealers and distributors have access to an Allison software to check driveline acceptability also.

The selector you use has to match what's called the shift mask in the TCM you are using. The selector positions on the selector must match what's available in the TCM. There's D-4-2-1, D-4-3-1 and D-3-2-1.
You'll have to also have a TCM that is programmed to use a mechanical throttle position sensor. The TPS should be mounted with a yield link connecting it to the engine throttle so if the TPS cable sticks, the engine isn't stuck a full throttle....yikes.
The TPS should also be mounted with a generous bend in the cable. The TPS body should be above its connection to the engine throttle to prevent moisture from making its way down the cable into the TPS itself.
And of course you have to wire in the transmission control system. Make sure you use battery direct power and ground where it's required.

I'm sure there's more, but that's all I can think of right now.
dbarton291 is offline   Reply With Quote
Old 01-10-2019, 06:30 PM   #4
Junior Member
Join Date: Jan 2019
Posts: 5
Thanks for your input!

I'm more interested in improving my top end speed (not anything crazy, but a steady 75 MPH would be nice) than I am in fuel economy. Anyone have experience with a low stall converter and how much difference that made?

I'm still learning, so keep it coming, please.
1997 Newmar Kountry Star FRED
Freightliner Chassis, Allison MT 542, Banks Stinger
NewmarKS1997 is offline   Reply With Quote
Old 01-20-2019, 01:55 PM   #5
Junior Member
Join Date: Jan 2019
Posts: 5
So has anyone out there upgraded the torque converter in the AT 542? If so, what did you use and how well did it work?
1997 Newmar Kountry Star FRED
Freightliner Chassis, Allison MT 542, Banks Stinger
NewmarKS1997 is offline   Reply With Quote
Old 03-09-2019, 07:47 PM   #6
Senior Member
Kiss4aFrog's Avatar
Join Date: Aug 2012
Location: WI 54016
Posts: 113
Still looking
Kiss4aFrog is offline   Reply With Quote
Old 03-11-2019, 09:16 AM   #7
Senior Member
Join Date: Apr 2009
Posts: 456
Unless the aftermarket has come up with something I don't know about (which is possible), there is no upgrade to the torque converter of an AT540/542/543/545 that will increase your top speed.
You can't add lockup. There are not available different stall torque ratios available, etc.
That's why the swap to the MT643 was so popular.
dbarton291 is offline   Reply With Quote
Old 03-11-2019, 09:29 AM   #8
Senior Member
Join Date: Jul 2014
Posts: 17,252
You don't mention engine RPMs when you start loosing speed climbing hills.
If the RPMs remain high while climbing, then its a converter issue. If the RPMs drop, you have an engine power issue.
twinboat is offline   Reply With Quote
Old 03-18-2019, 06:55 PM   #9
Senior Member
Join Date: Mar 2010
Location: maryland
Posts: 155
Anyone wanting to maintain speeds in excess of 70 mph might want to do some research tire speed maximums.

05kstar is offline   Reply With Quote

allison, upgrade

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Allison 2100 verses the allison 1000 BobnMelba Workhorse and Chevrolet Chassis Motorhome Forum 6 03-21-2014 10:40 PM
Allison still shuddering. Allison 3000 Mystery Allison Transmission Forum 23 01-18-2014 06:45 PM
Allison AT 542 Transmission Question. MartinP Allison Transmission Forum 7 10-05-2012 12:45 PM
Four Speed Questions (AT 542) Damon92 Allison Transmission Forum 12 10-02-2012 06:30 PM
Allison Expert on the Power Train Garage (Allison Transmission) Forum hzjcm8 Monaco Owner's Forum 3 04-25-2011 05:50 AM

» Featured Campgrounds

Reviews provided by

Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 07:36 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.