Overdrive on a GM chassis

steigerhouse · 06-14-2008, 06:19 PM

This is a question for you "gearheads" out there. I have a 1992 Fleetwood Flair 26 foot motorhome on a Chevy P-32 chassis. On a recent trip I had a problem crop up that has happened before. The engine is a 454 cu. inch with fuel injection and electronic ignition. The transmission is automatic. It has 1, 2, D and D with overdrive. The problem that has cropped up is that if I am descending a steep grade and slow down and drop the transmission down into second gear to let the engine help hold back the vehicle and save the brake linings, after getting off the grade and shifting back into D with overdrive, the overdrive does not work. The only way to get the overdrive working again seems to be to pull off the road, turn off the engine, sit there for a few minutes and then start back up. After doing that the OD works just like it should again. Any ideas what could be causing this or how to prevent it from happening in the future would be greatly appreciated.

z07 · 06-14-2008, 06:56 PM

Do you have a suplimental trans-oil cooler in addition to the one in the main radiator?

steigerhouse · 06-14-2008, 07:11 PM

Yes, I do have an auxillary transmission oil cooler. Are you thinking heat buildup in the transmission? That was my first thought, but I would think it would cool off under normal conditions and that doesn't seem to happen. I can drive normally on the interstate for an hour after this happens and it won't correct itself till I pull over and shut down.

leolkfrm · 06-15-2008, 05:45 AM

Welcome to the forum
I think you are misinformed about you unit, chevy P32 chassis didn't come out till 1998. You have a P30 chassis with a corporate transmission, Do not follow the instructions for a p32 (which has an allison) or you will hurt the tranny. the most it will tolerate is dropping into drive unless you are decending extremely slow.
Maybe someone who knows transmissions better can tell you what actually what happens when you create too much pressure in a corporate tranny( I know its not good).
One must learn different driving techniques when driving larger vehicles as they are different then cars, for ie. you should be 5 under the speed limit at the top and stab brake on the way down when you gain 10 mph over your selected downhill speed.

06-14-2008, 06:19 PM	#1
steigerhouse Junior Member Join Date: Jun 2008 Posts: 2	Overdrive on a GM chassis This is a question for you "gearheads" out there. I have a 1992 Fleetwood Flair 26 foot motorhome on a Chevy P-32 chassis. On a recent trip I had a problem crop up that has happened before. The engine is a 454 cu. inch with fuel injection and electronic ignition. The transmission is automatic. It has 1, 2, D and D with overdrive. The problem that has cropped up is that if I am descending a steep grade and slow down and drop the transmission down into second gear to let the engine help hold back the vehicle and save the brake linings, after getting off the grade and shifting back into D with overdrive, the overdrive does not work. The only way to get the overdrive working again seems to be to pull off the road, turn off the engine, sit there for a few minutes and then start back up. After doing that the OD works just like it should again. Any ideas what could be causing this or how to prevent it from happening in the future would be greatly appreciated.

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06-14-2008, 06:56 PM	#2
z07 Senior Member Join Date: Feb 2008 Posts: 391	Do you have a suplimental trans-oil cooler in addition to the one in the main radiator?

06-14-2008, 07:11 PM	#3
steigerhouse Junior Member Join Date: Jun 2008 Posts: 2	Yes, I do have an auxillary transmission oil cooler. Are you thinking heat buildup in the transmission? That was my first thought, but I would think it would cool off under normal conditions and that doesn't seem to happen. I can drive normally on the interstate for an hour after this happens and it won't correct itself till I pull over and shut down.

06-15-2008, 05:45 AM	#4
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 4,908	Welcome to the forum I think you are misinformed about you unit, chevy P32 chassis didn't come out till 1998. You have a P30 chassis with a corporate transmission, Do not follow the instructions for a p32 (which has an allison) or you will hurt the tranny. the most it will tolerate is dropping into drive unless you are decending extremely slow. Maybe someone who knows transmissions better can tell you what actually what happens when you create too much pressure in a corporate tranny( I know its not good). One must learn different driving techniques when driving larger vehicles as they are different then cars, for ie. you should be 5 under the speed limit at the top and stab brake on the way down when you gain 10 mph over your selected downhill speed.