I own a 1981 Trabant 601.
It uses a Sprag clutch between 4th gear and the input shaft which allows the drivetrain to freewheel under cruise. It's purpose is to prevent the driver from using the engine as a brake going down hills to avoid engine damage because the motor is a 2 cycle.
These Sprag clutches are notorious for not engaging. It's got these rollers inside that when a small amount of torque is applied will lock 4th gear. Supposably either the rollers wear down or the drum develops flat spots which causes them not to engage. However I think my transmission is gunked up because it seems everytime I do a fluid swap or replace it with something else, the problem goes away for awhile.
Here is a photo of the device:
The gear oil: Depending upon which Eastern Bloc country you lived in at the time you could use about five different types of lubes. In the DDR it was HPL 68. The shop manual says if this oil could not be sourced to use SAE 30. Which is what NAPA's cross reference manual says to use.
I cannot find this HPL 68 anywhere in the United States. When I Googled it, all the websites were in Europe. I did find ISO 68 at Tractor Supply. Could this be the same thing just a different designation?
This is sort of a long story so I'll try to condense it as much as possible.
It was suggested by an owner in the Czech Republic I run diesel fuel in the transmission for 300 miles. I thought that was excessive so I only drove the car for 10 miles with an instant improvement, then drained it out and tried 10W30 with some success.
Here is what I have used so far, in no particular order.
1) Diesel fuel : no freewheel device engaging issues whatsoever!
2) 10W30 : This is what is in the gearbox now. With this stuff I have to drive the car about 2 to 3 miles before 4th gear wants to engage (25F). Afterwards it engages so-so. Meaning it either engages smoothly in and out of cruise, delays followed by a loud "thud", sometimes under low RPMs I may have to go back to 3rd, wind the motor up then shift into 4th gear. But I can also put the transmission into 4th while not moving (at idle speed) and stall the engine.
3) SAE 30 : (as stated in the handbook can be substitued for HLP 68) : Initially this was what I used not long after I got the car along with White Shepherds stop leak to sweal up a leaky axle seal. This oil seemed to work fine even in sub freezing weather. Then the freewheel device developed issues engaging in the middle of summer. As of right now the freewheel device does not seem to like this stuff at all! In cold weather anyway.
4) Dextron III: One owner reported she had used this fluid for 20,000 KM with no ill effects so I tried it. After the first issue with the freewheel device back in 2013, I switched to this for about a year and saw an instant improvement with no issues until the end of this summer. I'm not sure why.
What I am trying to figure out is if the Sprag clutch is worn out is thinner weight oils allowing it to engage easier? Or is it possible the transmission has 35 years of gunk buildup that is breaking up over time clogging up the roller bearings in the clutch?
If I knew it would not harm the transmission, I would use diesel fuel because it engages with no issues but I realize diesel fuel is not a lubricant. It is an oil but probably the the thinnest weight oil from petroleum.
I got to reading and found out BMW motorcycles use these Sprag clutches in the starters and they suffer from gunk buildup. One guy says to use a 25% mixture of Risolene in the gearbox, run it until the problem goes away and replace with fresh oil. I have not tried this. One guy I know said he used this in an engine and it locked it up 15 minutes later. He said it was a caustic based solution. His engine may have had some other issue.
I did buy a quart of Risolene and was going to test it on an old engine part to see if it actually eats off any oil residue.
A guy at Autozone said to use a mixture of Marvel's Mystery oil but the thing is I've heard this is relabled automatic transmission fluid which is what I have used. Is MMO really ATF?
One thought was to try 0W30 motor oil. Since that is technically 30 weight oil but is actually thinner at colder temperatures. I know that the transmission does not generate allot of heat simply because I have drained it out after a drive and it's like luke warm.
It's been very cold here in the southest this past week so I can't expect too much from a 30+ year old car. Perhaps when it warms up the 10W30 would work just fine. I normally don't drive this car in the winter due to it's poor heater.
Any Sprag clutch experts out there who could shed some light on what might be up with this device?
Any safe lubricants I could use in this gearbox other than SAE 30?
It uses a Sprag clutch between 4th gear and the input shaft which allows the drivetrain to freewheel under cruise. It's purpose is to prevent the driver from using the engine as a brake going down hills to avoid engine damage because the motor is a 2 cycle.
These Sprag clutches are notorious for not engaging. It's got these rollers inside that when a small amount of torque is applied will lock 4th gear. Supposably either the rollers wear down or the drum develops flat spots which causes them not to engage. However I think my transmission is gunked up because it seems everytime I do a fluid swap or replace it with something else, the problem goes away for awhile.
Here is a photo of the device:
The gear oil: Depending upon which Eastern Bloc country you lived in at the time you could use about five different types of lubes. In the DDR it was HPL 68. The shop manual says if this oil could not be sourced to use SAE 30. Which is what NAPA's cross reference manual says to use.
I cannot find this HPL 68 anywhere in the United States. When I Googled it, all the websites were in Europe. I did find ISO 68 at Tractor Supply. Could this be the same thing just a different designation?
This is sort of a long story so I'll try to condense it as much as possible.
It was suggested by an owner in the Czech Republic I run diesel fuel in the transmission for 300 miles. I thought that was excessive so I only drove the car for 10 miles with an instant improvement, then drained it out and tried 10W30 with some success.
Here is what I have used so far, in no particular order.
1) Diesel fuel : no freewheel device engaging issues whatsoever!
2) 10W30 : This is what is in the gearbox now. With this stuff I have to drive the car about 2 to 3 miles before 4th gear wants to engage (25F). Afterwards it engages so-so. Meaning it either engages smoothly in and out of cruise, delays followed by a loud "thud", sometimes under low RPMs I may have to go back to 3rd, wind the motor up then shift into 4th gear. But I can also put the transmission into 4th while not moving (at idle speed) and stall the engine.
3) SAE 30 : (as stated in the handbook can be substitued for HLP 68) : Initially this was what I used not long after I got the car along with White Shepherds stop leak to sweal up a leaky axle seal. This oil seemed to work fine even in sub freezing weather. Then the freewheel device developed issues engaging in the middle of summer. As of right now the freewheel device does not seem to like this stuff at all! In cold weather anyway.
4) Dextron III: One owner reported she had used this fluid for 20,000 KM with no ill effects so I tried it. After the first issue with the freewheel device back in 2013, I switched to this for about a year and saw an instant improvement with no issues until the end of this summer. I'm not sure why.
What I am trying to figure out is if the Sprag clutch is worn out is thinner weight oils allowing it to engage easier? Or is it possible the transmission has 35 years of gunk buildup that is breaking up over time clogging up the roller bearings in the clutch?
If I knew it would not harm the transmission, I would use diesel fuel because it engages with no issues but I realize diesel fuel is not a lubricant. It is an oil but probably the the thinnest weight oil from petroleum.
I got to reading and found out BMW motorcycles use these Sprag clutches in the starters and they suffer from gunk buildup. One guy says to use a 25% mixture of Risolene in the gearbox, run it until the problem goes away and replace with fresh oil. I have not tried this. One guy I know said he used this in an engine and it locked it up 15 minutes later. He said it was a caustic based solution. His engine may have had some other issue.
I did buy a quart of Risolene and was going to test it on an old engine part to see if it actually eats off any oil residue.
A guy at Autozone said to use a mixture of Marvel's Mystery oil but the thing is I've heard this is relabled automatic transmission fluid which is what I have used. Is MMO really ATF?
One thought was to try 0W30 motor oil. Since that is technically 30 weight oil but is actually thinner at colder temperatures. I know that the transmission does not generate allot of heat simply because I have drained it out after a drive and it's like luke warm.
It's been very cold here in the southest this past week so I can't expect too much from a 30+ year old car. Perhaps when it warms up the 10W30 would work just fine. I normally don't drive this car in the winter due to it's poor heater.
Any Sprag clutch experts out there who could shed some light on what might be up with this device?
Any safe lubricants I could use in this gearbox other than SAE 30?
