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Fluid Level on Allison 6-Speed

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05-27-2007, 04:02 PM
Frank Strong
Fluid Level on Allison 6-Speed
I just returned from a 400 mile trip and noticed, for the first time, a burp of transmission fliud come out of the breather hole at the front of the tranny. When I checked the fluid level on the dipstick, it appears to be overfilled. When cold and idling, the level is half up the hot range. Should I pump out some fluid or just leave it as is? The fluid is clean and clear. The only problem I've ever noticed on the tranny is that when it downshifts all the way to 1st gear, sometimes it will slip a little before it catches ---- otherwise it has been flawless.
I have a 94 Regency 34 ft with the Cummins 300HP setup.
I know that in the auto world, it's not good to overfill the tranny, but I'm not aware of any serious problems caused by overfilling. I'm not very practiced on the these big rigs, so I thought it smart to ask the pro's before making a decision.
Thanks for any help you can give me.


Frank Strong
1994 Regency 34ft
300 HP Cummins, 6 spd Allison
Spartan MM Chassis
05-28-2007, 05:28 AM
Bill N.Y.
Lower the level to the correct height. If Allison recommends a certain height, who are we to second guess that? They designed the system, so follow their level recommendations.

Problems you can have by overfilling...
1) you'll cause seals to leak.
2) your vent tube will seep fluid.
3) you can cause air bubbles and foaming of fluid. You can compress air bubbles easier then fluid. Proper psi readings will flucuate with foaming of fluids.

And above all... Make certain that you have the correct dipstick!


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8908 0128 40RDS-C1
L-10 Cummins
Allison MT647 Transmission
Spartan Chassis
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05-28-2007, 11:33 AM
Frank Strong
Bill, I just pumped 3qts of tranny fluid out of my unit to bring it into the proper cold range. When I drove it around the block for a test drive, I could tell a noticeable difference in the smoother shifts. I hope it hasen't been damaged. I have owned this Barth for about a year and drove it all the way to CA from FL this past summer without any problems. I purchased it from a Lazy Days dealer near Tampa. They really bragged about their service dept but I found several other things that weren't done like greasing the chassis.

If you want it done right, you must do it yourself. But this big rig is a real test of my skills, equipment and capability.

Thanks for your help!


Frank Strong
1994 Regency 34ft
300 HP Cummins, 6 spd Allison
Spartan MM Chassis