J type laycock overdrive gets hot

[Gavin]

We have two J type Laycocks being prepared for use in Model A's. Prior to installation we are bench testing them using a rig described on Buckeye Triumph's website which is very helpful. Having filled them with a quart of 85/90 we find they both get hot to the point where it is not comfortable to hold your hand on the case after only 10 minutes of running. This is with the overdrive either disengaged or engaged. We appreciate that in a car being driven there would be some airflow over the unit which would assist with cooling. Does anybody have any experience with the operating temperatures of these o'd's? I am unable to find anything on the Web. The operating pressures are between 460 and 520 psi.
Cheers,
Gavin

[pooch]

What car are these J types out of ?

For example an MGB recommends 20/50 oil for box and overdrive at 420 PSI.

85/90 in these over pressurize them .

[Brian T]

I have overhauled many J type overdrives, I cannot say I have ever checked the temperature, unless you have a slipping condition in the engaged - disengaged position (very unlikely with 2 units) I would flush out the 80/90 and refill with F type ATF --- NOT Dextron,
Regards Brian.

[Dick M]

I have run my J type Laycock od with 10-30 motor oil for 4k miles without incident. Perhaps the 80-90 is too heavy for the Laycock.

[Brian T]

I meant to add that 10-30 is acceptable, for that matter they worked fine with 90W for many years, if remember the F type ATF has better anti foaming agents, in addition the lighter fluids allow easier shifting in cold weather.

[BILL WILLIAMSON]

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In factory installations they are attached to the transmission & the oils for each unit is shared. This probably helps in keeping it cooler.
"Somewhere" I heard of someone fabricating a larger sump for the overdrive, for more oil capacity. I've worked on the Model J, in Volvos & Jaguars, they are a much stronger unit than the earlier type. The Model J can be identified by the LARGE, screw in type solenoid, that requires NO adjustment. When a cause for a NO SHIFT condition can't be found, & the oil level's full, it's usually a solenoid problem, even though the operating piston in it appears O.K. & the windings test O.K. They're a GREAT unit, BUT Yo' wallet will be in "SHOCK" when you have to buy parts for it!!!!! And, DO use A.T.F. in it, & it will probably run cooler.
Bill W.

[Gavin]

Thanks for your replies to date, much appreciated as we have no personal experience with these. The units are from Triumph 2000 or 2500 saloons which used the 85/90 oils. The quantity we have put into the o/d's appears to be about half of what was put into the car gearbox from which the o/d was fed. I expect most folk never bench run these so don't get to notice the heat nor do they put their hands on an o/d which has run some miles in a car. One of the o/d's shifts fine while the other is a little slow. Trying ATF sounds like a good option after which we may reduce the pressure in the high one. Cheers, Gavin.

[Boston Bruce]

I use 10W30 synthetic in mine and I don't think it runs hot. Had one in my Austin Healey 3000 in the late 1960s and I abused it plenty. Always ran great.