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GM 4L80e

Bullybeef

By Bullybeef
in Ask A GM Technician

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Bullybeef Enthusiast

Bullybeef

Posted
Posted

Hi new to this so here goes

 

Can anyone advise me

 

I have a 1971 gulfstream sunsport motorhome with a GM 4L80E box

 

For some reason the van will not move

The engine starts and I can select gear, but the engine just revs when I push the throttle . I have checked the level of ATF and it is fine

However there is a small leak of fluid under the van

Could this be the problem or so it more severe

 

Hope someone can offer some advice

Bullybeef Enthusiast

Bullybeef

Posted
  • Author
Posted

Have now thought that there was no fluid on the floor under the van,before I decided to add 2 litres to see if this made any difference, the fluid on the floor after this could be because it was over filled.

Could be one of several things is not really helping

 

Can you expand please

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

Hi new to this so here goes

Can anyone advise me

I have a 1971 gulfstream sunsport motorhome with a GM 4L80E box

For some reason the van will not move

The engine starts and I can select gear, but the engine just revs when I push the throttle . I have checked the level of ATF and it is fine

However there is a small leak of fluid under the van

Could this be the problem or so it more severe

Hope someone can offer some advice

The 71 Gulf Stream did not come with a 4L80E unless a Powertrain swap was done ....

 

If an automatic tranny doesn't move with oil and the engine is turning in gear , you have BIG problems ,

 

If you have a THM400 ( pre 4l80) then it's forward clutch or direct clutch may have gone bye bye ,( common)

 

See a shop , nothing you can do I'm afraid

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

The 4L80E did not go into production after your motorhome was 20 years old. As govtech4 said, your truck has had a drivetrain swap done. The transmission you now have is controlled by electric solenoids, and likely has a TCM (transmission control module). They had to either create or adapt a wiring harness to work in your motorhome.

 

Do you know what engine you have? Are you sure you do not have a Turbohydramatic 400 transmission? Really can't see why they would remove what was likely a 454 with the TH-400 transmission for any of the new engines.

 

You said that you added fluid so it may be overful now, is there not a dipstick on the transmission?

Bullybeef Enthusiast

Bullybeef

Posted
  • Author
Posted

The 4L80E did not go into production after your motorhome was 20 years old. As govtech4 said, your truck has had a drivetrain swap done. The transmission you now have is controlled by electric solenoids, and likely has a TCM (transmission control module). They had to either create or adapt a wiring harness to work in your motorhome.

 

Do you know what engine you have? Are you sure you do not have a Turbohydramatic 400 transmission? Really can't see why they would remove what was likely a 454 with the TH-400 transmission for any of the new engines.

 

You said that you added fluid so it may be overful now, is there not a dipstick on the transmission?

The 4L80E did not go into production after your motorhome was 20 years old. As govtech4 said, your truck has had a drivetrain swap done. The transmission you now have is controlled by electric solenoids, and likely has a TCM (transmission control module). They had to either create or adapt a wiring harness to work in your motorhome.

 

Do you know what engine you have? Are you sure you do not have a Turbohydramatic 400 transmission? Really can't see why they would remove what was likely a 454 with the TH-400 transmission for any of the new engines.

 

You said that you added fluid so it may be overful now, is there not a dipstick on the transmission?

Bullybeef Enthusiast

Bullybeef

Posted
  • Author
Posted

I have been told it is a 4l80e by the local Rv company

I am now doubting them

The shift gears are

P R N D D(boxed) 1 2

Bullybeef Enthusiast

Bullybeef

Posted
  • Author
Posted

if I rev the accelerator pedal up and down, the vehicle will slowly move forward and also in reverse but i then turn off the engine and the same thing happens no drive

 

I don't know much about auto transmissions but it seems like i am moving the shift stick to any gear and it does not engage the gear, there is transmission fluid in the box and the selector on the side of the box is moving when i shift the gear

 

sorry in my earlier post i stated 1971 it is a 1993

patriot Enthusiast

patriot

Posted
Posted

Since you wan t an unseen diagnosis, it sounds like a bad torque converter.

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

My bet is on the magic box that was installed to allow that transmission to work on that year model vehicle. Either the box itself or the wiring related to it ... and there's ALOT of wiring ...

 

Snap a pic of the transmission oil pan - that will tell us once and for all what tranny is in that thing ...

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

if I rev the accelerator pedal up and down, the vehicle will slowly move forward and also in reverse but i then turn off the engine and the same thing happens no drive

 

I don't know much about auto transmissions but it seems like i am moving the shift stick to any gear and it does not engage the gear, there is transmission fluid in the box and the selector on the side of the box is moving when i shift the gear

 

sorry in my earlier post i stated 1971 it is a 1993

 

You should find someone local to you that can plug a scan tool into the diagnostic port and see if there are any codes in the transmission. Since it does not move, they will have to come to you. Can't imagine towing a motor-home anywhere is cheap.

 

Since you wan t an unseen diagnosis, it sounds like a bad torque converter.

 

First tip I was given by the old guy that trained me on torque-flytes was "have not seen a torque converter fail, ever". He had worked at the same Plymouth dealership (many different owners, same building) since 1949. This was in 1980. Oddly enough within a year Chrysler had an issue with input shafts not being machined correctly and they were taking the splines out of the turbine. Transmission would have correct pressures at all the test ports, but car would not move. Put a new converter in it, and it would work for about 5k. Point here is, not going to be the converter alone.

This is not going to be something the OP can fix himself. About all he can do is make sure the fluid level is correct.

 

My guess is the pump. To test it, take one of the cooler lines off the radiator and redirect it to a can. I have no idea which one is the pressure side, so I would also find a way to redirect the other end to a can as well. Start the motorhome. If the pump is working you should see a pretty good stream of fluid coming out of the line or radiator. You need only run the engine for 10 or 15 seconds to see if it is working. If you want to go one step further, see if you can figure out which of the lines is the pressure side, and then disconnect the other line from the radiator or cooler. Make sure the fluid is coming out of the radiator as good as it did from the line. In other words, check to see if radiator trans cooler is plugged. I still wonder why you can't verify the proper level of trans oil though.

If the cooler or rad is plugged, that will require a removal of transmission, and at minimum a replacement of the torque converter due to the lockup clutch fibres delaminating and plugging the cooler.

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