6V92TA Drive Train Performance

[khpaladin]

We got our 'NellyBelle' (DW named her) in '98. She is an '81, 40ft coach, with a 6V92TA pre-DDEC, w/335hp (we were told, I'm not sure), w/ an Allison MT654CR 5-speed auto, and a Rockwell 3.70:1 rear axle ratio. We had a reputable shop do an in-frame on the engine, overhaul the tranny and differential, and do a mated dyno on the drive train. We have a GVWR of 35200, but are running about 31400, and pulling an '86 Honda Accord.

Initial start-up gives a small amount of white smoke and then runs clear at idle. All fluids are good with color and levels. I was told to keep the engine oil level about a quart low to minimize 'slobber' tube flow. This seems to work well and does not change oil pressure or temperature levels. Though we can run 75+ on the flat, we run 65 at about 1900rpm for fuel economy, and no exhaust trail. We get good takeoff from a standing start with a small puff of dark smoke, easy merging on the flat. When hitting small hills we start to loose power, and on 6% plus grades we can go down to 35-40 mph at about 2100-2200rpm with clear exhaust. On the flat we get around 11mpg, on hills we get around 5-6mpg, and overall average about 7-8mpg.

Since I have no background in diesel engines, I rely on others for diesel information and performance, and am not sure what the correct question should be. I've been told that this drive train should perform a lot better on hills, so I'm not sure it's suppose to loose that much power. I've been told to adjust my turbo boost, which I don't understand what that is, and don't think I have it. Just wondering if other coaches with similar drive trains are having this problem or is it just the nature of the beast and we live with it.

Best Regards

[rellick]

Was your engine just rebuilt or was this a worsening symptom? Have you changed fuel filters? Sounds like its not getting enough fuel.

[bluesky]

sounds much like the performance we get from our '83 with a 6v92 and allison transmission.

[khpaladin]

Originally Posted by rellick

Was your engine just rebuilt or was this a worsening symptom? Have you changed fuel filters? Sounds like its not getting enough fuel.

Kieth,
In '99 we had the engine diagnosed and an in-frame overhaul, replacing some sleeves, pistons, injectors, bearings, seals, and gaskets. The transmission was also overhauled and with an overhaul kit, and the turbocharger was rebuilt. The differential was drained, inspected, resealed, and filled. The drive train was then put thru a mated dyno. We did not take the coach out much for the following four years due to existing work schedule, however when we did, we noted there was a lack of power during acceleration. The shop could not find anything wrong, but in '05 during an annual service in Utah I noted a 'dust trail' from one of the turbo connection sleeves, the tech checked and found an over-sized band, the band was replaced. This seemed to produce additional power, but not on hills.

The two original fuel filters were replaced with a DavCo 382 fuel pro system in '99, and the fuel cartridge had been replaced about 6 months ago, and the filter level is about 1.5 inches from the bottom.

Hope this help

[khpaladin]

Glenn,

I admit that's a possibility and will accepted it if true. But from reading the web it appears that this engine/transmission combo with the maxed out horsepower, and rear end ratio should at least hold upwards of 60mph on grade. Just curious on why our coach does not seem to be able to do that with the weight we're pushing.

[bluesky]

... most of our driving is in the mountains at high elevation, we live in BC Canada. This could be a major factor in my grade speed.

[Chester B. Stone, Jr.]

I have owned six motorhomes and none would ever do 60 on a steep grade. If it would, I would say it is over powered.