turbo 400 tranny

RCMAN46 wrote:
The torque rating of the turbo 400 (450 ft lbs conservative) will most likely be OK. After all they put the 400 behind 454 big blocks which probably had more torque than a 4 cylinder diesel. The problem you may have is the torque converter. It was designed for a much higher rpm engine than the diesel.

Converter for a 6.5 diesel might work...or the one used behind the 3.9 Cummins.

i understand trying to squeeze every mile you can out of a drop of fuel, but...
at what point does adding all the extra cash for things like a Banks(expensive) system or deisel engine or whatever outweigh the benefits?
what are you going to gain in fuel savings over X time frame and what did the modifications take away from those savings?
need to get out the old calculator and go to work....

Overdrive may or may not help. The problem is that if the engine is underpowered, it will need to downshift all the time to maintain speed. If it shifts too often, it will kill any gains from turning the engine slower. To make the whole thing work, for that coach, you probably want about 250 HP (assuming diesel) That would give you enough that you could probably get away with overdrive, assuming the diesel has a decent torque rating - like 600 ft-lbs or better. You start getting less torque than that, and it will want to downshift over the smallest grades, so gearing won't help much.

For comparison, even though I've got a gasser, but I'm running nearly 600 ft-lbs of torque. Total weight including toad is almost 19K lbs. I'm running a 4L85E, so it has overdrive and lock up TC. I have no trouble staying in lock up most of the time. I could get away with lower differential gearing - right now I turn about 2100 RPM @ 60 mph. I have a friend who is running the same coach, same gearing, same trans, but a different engine. He is running around 450 ft-lbs of torque and has trouble staying in lockup. Some of that may be programming, but I think torque is playing a significant roll as well.

That should give you a good point of reference. Don't worry about the fact we are running gassers, as its the numbers that matter, not the fuel. I stating that I assumed you were talking about diesel because 600 ft-lbs is not commonly found in a gas engine.

As far as Banks, mostly that just helps power, it is unlikely it will effect mileage by any significant amount. Multiple real life reports from users on RVnet concur.

What I want is fuel mileage. The most I can possibly squeeze out of it. What is a Banks system? I have seen motorhomes with that name on the side. Also would installing an over drive give me a better mileage?

I had a 6.5 in a 4dr duelly once w/T400 trans.....got around 16--18mpg but didn't have much power towing until I installed a Banks system and an inner cooler. We still have a 1994 full size Blazer with the 6.5 motor that has about 300,000mi on it and still gets around 22mpg on the road. That T400 will hold up---I even use it in my race car.

How much mileage would I get if I put in the 6.5 diesel that was hooked up to a turbo 400 in a schoolie. Would it be better? This HR feels so heavy It feels real heavy.

What Diesel did they put in it. Isuzu Diesel was an option for Revcon of that same time period. It was an unbelievable dog. Considerably less HP that the 454. Considerably less torque than the 454. While the mileage was 14 mpg+, it couldn't get out of its own way. The Revcon is no doubt lighter than the HR, so that would only aggravate the problem.

The torque rating of the turbo 400 (450 ft lbs conservative) will most likely be OK. After all they put the 400 behind 454 big blocks which probably had more torque than a 4 cylinder diesel. The problem you may have is the torque converter. It was designed for a much higher rpm engine than the diesel.

The first question I have is the torque rating of the transmission. Then the shift RPM would be for a gas engine. It might work but for how long.

Shane,

If you want to spend the money, you can put just about anything in or on anything.

As the Isuzu engine was supplied to GM at one time, bell housings and adapter plates and parts are probably available with GM part numbers. If not, then someone probably supplies the kit.

Matt