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OK to use thinner gear oil in winter?

3K views 3 replies 3 participants last post by  jseabolt 
#1 ·
My Trabant 601 calls for a hydraulic oil called HLP 68. If you try to find this oil in the United States you will find it doesn't exist. HLP is just a German designation. But it's basically a mineral oil with zinc additives.

I did cross reference it over to Mobil DTE 26 (in 5 gallon buckets). However Tractor Supply sells a brand called Mystik ISO VG 68 in a 2 gallon jug which according to the MSDS is the same thing as HLP 68. And O'releily's sells an AW 68 but don't know if it contains any anti-wear additives (zinc).

The sprag clutch in 4th gear has issues engaging below 50F. I was told when this happens the device is worn out (or gummed up) but I'm thinking I can get more life out of it by using a thinner oil.

It's common to occasionly flush the transmission with diesel fuel to get all the gunk out of it which can cause issues with this clutch.

I did a double diesel fuel flush (5 miles up the road, drain , replace ) and washed a bunch of silver sludge out of the transmission then replaced with Mercon ATF. Now it engages much better. Still some issues for the first mile or two but once it engages it works great the rest of the day.

I've used several different types of oil. Initially I used SAE 30 then switched to Dextron. I've tried 10W30 and 0W20.

What I don't understand is why 10W30 seems to work better than 0W20. Wouldn't 0W20 actually be "thinner" in cold weather over 10W30?

Diesel fuel actually works the best with no trouble at all engaging at all when cold but is not a lubricant.

I found this viscosity versus temperature chart:



Is it safe to say that I could use AW 32 during the winter? Then switch back to AW 68? Or use a multi viscosity hydraulic oil year round? Which was not available back in the 1950s?

Based on this chart it's saying AW 68 is good for temperatures up to around 210F. The transmission get's nowhere near that hot. And AW 32 is good for up to around 140F. I doubt the transmission get's anywhere near that tempetature in the middle of summer either.

Also what's weird is ATF is the same viscosity as SAE 20 motor oil but seems to work better. So what is so special about Mercon/Dextron fluid over motor oil?



I was told that the engineers who designed this transmission back in the 1950s came to the conclusion that AW 68 was the best oil to use. However keep in mind all or most petroleum products were supplied to East Germany by the Soviet Union back in those days and the mineral oil used in the transmissions probably contained no additives. So it's possible that this VG of mineral oil was all that was available or most common.

Just wondering how automotive engineers come to the conclusion which gear oil is best. Do they take the operating temperature into consideration?

O'Reliey's sells a multiweight hydraulic oil AW32/46/68 in a 5 gallon bucket. That might be a good year round oil to use if the AW 32 works well in the winter.

I have this Mystik AW 68 in the transmission right now but have not been able to drive the car because of all the snow on the roads.

I was just wondering if the operating temperature does not exceed a special temperature I could get away with using a thinner oil.
 
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#3 ·
Transmission oil is more than just a lubricant. It needs to have the right Coefficient of Friction for the clutches to do their job. Too slippery is just as bad as not slippery enough.
I'd do as Dan suggested and contact Amsoil. The other contact might be the folks over at Brad Penn (formerly Kendall). Ive had very long and helpful conversations with people from both.

My concern with a fly weight oil would be insufficient film strength for the clutches
 
#4 ·
I seen that 22/32/46/68 multi-weight hydraulic oil on the web. At $160 for a 5 gallon bucket it ought to be good!

I'll send AMSOIL an email. Hope I don't sound pessimistic but I've sent several oil product companies emails about their product and have yet to get a reply!

It would be nice if AMSOIL would sell me a sample (2 quarts) to try out. If it works great then yeah I'd buy a 5 gallon bucket. I'm sure I could break it up into quarts and sell it to my Trabant friends. There are 150 of us in the United States.

This Sprag clutch looks like this:







It's more of a one way bearing than an actual clutch. Just a bunch of rollers that makes contact with the input shaft and 4th gear held in place by a cage.

It's not like a "wet clutch" or anything like that. Supposably this same type of device is found in allot of older GM and Mopar automatics.

If you could imagine an automatic transmission slipping when cold then engages when it warms up. My "cheap" boss as an S-10 pickup like this. He says he has to let it warm up for about 15 minutes before he can drive it.

In my case below 50F it doesn't want to engage until the car is driven for a few miles. It's as if 4th gear is not there. It's there to prevent the driver from using the engine as a brake going down hills to prevent starving the engine of oil (being a 2 cycle).
 
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