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Triumph TR6 - Oil for gearbox j-type

I have a 1975 TR6 with a j-type overdrive and want to know what kind of lubrication to put in the gearbox. There seems to be conflicting views on what weight of oil to use...anything from regular gear oil to standard weight engine oil (10W30) to single weight non-detergent 30weight.

Any suggestions?

I just purchased 74 TR6 with J type overdrive. I drained gearbox and cleaned sump filter (I did not try to clean pressure filter). Replaced oil with std 90 wt gear oil. Now overdrive is stuck in ON postion all the time(even with 12V disconnected from solenoid). I checked all electrics and they work fine. I also rechecked oil level and topped it off. I'm getting ready to pull overdrive solenoid to see if it is operating correctly. Given that it is OK, could the type of oil used in the gearbox make it stick in the ON position? What about GL4 gear oil Vs GL5 gear oil?
John Korsak

Hi John

I had the same problem when I first installed my O/D. While it would engage, I could not get it to disengage immediately. I don't believe that it is due to the oil but rather a sticking solenoid. I took mine out and bench tested it with 12V and saw that while it move one direction it didn't retract. I check to see if it drew the correct curent (i think 1.2 amps) . By working the soleniod back and forth manually while connected with votageand a switch I was able to finally free it and has worked ever since (4500mi). These tend to seize and can not be rebuilt and are VERY expensive.

They are also very hard to remove in a J-type b/c of the angle where it is and the chassis frame and the fact that you need a very thin wrench with an opening of 1". My solution was that I bought a Delta table saw wrench, filed it to the correct size and bent the wrench in a 45*angle. Slowly I was able to remove the 'noid at 1/8 turn at a has fine threads!

Thanks Steve!

I will take solenoid out and let you know what happens. I think that I will go back with GL 4 rated gear oil, as that seems to be the preferred choice from what I can tell from the archived messages that I've been reading.
John Korsak

I have a 1958 TR3A which I bought new. It came with an overdrive. Back then, they said don't use 80 or 90 oil. Use 30 non-detergent. They thought that the detergent would cause the cone clutch to slip. I went through 3 gearbox overhauls (very expensive) in 80,000 miles.

Since the restoration in 1990, (52,000 miles) I've only used Valvoline multi-grade 20W50 and I have had no problem. I change the oil in the gearbox - overdrive every 5000 miles.

Don't use synthetic oil in the gearbox. Racers I know have tried it and it is so slippry that the synchros stop working. One even went off the track with serious damage. Changing back to usual oil corrected the problem right away.

Don Elliott
Don Elliott

You were right about that stuck solenoid. My mechanic took it off, took it apart, cleaned it up, and put it back on. It works just fine now. While we were in there we also cleaned out the high pressure filter and well as the sump filter. I went with the GL 4 80-90 wt gear oil. Thanks again for your help.
John Korsak

Just completed a restoration on a TR4a. The overdrive a A type required rebuilding, poor oil pressure and broken thrust washers. On testing after rebuild the overdrive slipped in reverse, overdrive obviously not engaged. The EP90 oil was drained out and straight 30 sae engine oil replacing it. After bleeding the air out again, the overdrive seems ok now. I have some limited slip diff oil which I am tempted to try sometime.
dale moore

I have a '76 TR-6 with the J type overdrive. When I got the car last fall, the OD would not work reliably. I drained the gearbox and replaced the oil with standard 80w90 gear oil, as specified in the original owners manual that I have, and - problem solved.
Cris Hemingway

I have always used EP80 with no overdrive problems over more than 200,000 miles. One gear box chewed up a lay shaft bearing after about 120,000 miles. EP ( extreme pressure) lubricants are designed to withstand the very high pressures between two gear teeth, so why even think of using engine oil in a gearbox?
Peter Cobbold

Although it makes sense to use the EP 80, the Volvo dealers here use 30 weight or 10w30 non-detergent oil in the transmission with o/d. The Volvo 140 series and 240 series used the same o/d unit J-type Laycock. Apparently the hypoid oil causes problems in the 0/d as the oil is not compatible with the linings in the sliding cone.

This is what they tell me

Don has the right idea. There is a fine line between too thick and too thin an oil in the transmission. The problem with 90 weight is not just the overdrive but the countershaft in the bottom of the gear box. I overhauled the transmission on my TR250 2 years ago. The roller bearings on the countershaft where gone and the gear cluster had cutting into the shaft, both needed replacement. I used the 30 weight for a short time but on long runs I could feel the oil thinning out. Since changing to 20W50 the overdrive has been fine and gear box hasn't had that dry feeling.
Every time I change the engine oil the transmission oil gets changed also. Maybe over kill but its cheaper that an overhaul.

Phil Law

This thread was discussed between 30/05/2001 and 26/07/2001

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