Mobil 1 Synthetic 5W30 in Overdrive/Trans

[BrianN]

For about six months I have been running Mobil 1 Synthetic 5W30 in the trans and overdrive. This has apparently worked fine through all conditions, except that on my last extended drive in the heat the OD would seem to take extra time engaging and then release under load. As the day cooled off this condition went away.

How does this fit with the experience of others? Should I go back to non-Synthetic oil? Is this stuff too slippery or not pump up right under high heat?

 

[gonzo]

Hi Brian:

The transmission overdrive issue you described may be due to incorrect adjustment – but proper choice of oils may also be of involved.

For several years I’ve been using Castrol Syntex 20W 50 in the BJ-7 transmission with excellent results. The only time the overdrive failed to engage was on an extended trip to Park City, Utah (Conclave). Imagine I-80 through Bonneville Salt Flats without overdrive!!! Anyway, the overdrive was corrected with a simple adjustment of the rod located on the left side of the transmission. Carefully inspect that the rod clamp and bolt are secure and tight. After many years of service these two pieces tend to deform or stretch causing just enough slippage to disengage the overdrive entirely, like in my situation, or under certain conditions.

I haven’t had much luck with Red-Line’s MT product(s) which seems to be the preferred lubricant of choice for LBC; no problems with the Transmission’s O/D, but after 100 miles 3rd to 4th shifts started to graunch and they became difficult to engage! Things normalized after a couple of changes with Castrol Syntex.

Should you be interested in experimenting with the Red-Line product I have a few unopened bottles that I could offer. But I would encourage that check O/D adjustment and mechanism first. GONZO

 

[BrianN]

Thanks for the info. I'm assuming the Castrol Syntex you mentioned is a motor oil, like the Mobil 1 I am using. Maybe I should go to the heavier weight.

The dip stick only indicated 1/2 to the low mark. I topped it up and maybe that will do the trick. Problem is most of my driving is in cool to moderately warm conditions, not the extended driving 95+ ambient where there problem occurred. Next hot spell I will try to get the car out and test it.

 

[Keoke]

Yep Brian, a low oil level can cause the problem you described. However, I prefer,Assuming the actuator lever/rod,Mentioned by Gonzo, is tight,adding a thin gasket under the OVD relay housing to increase it's pull in range.---Fwiw---Keoke

 

[gonzo]

Castrol Syntex reference is engine oil. Most auto parts store stock it.

Good that you also checked and corrected trans oil level. But check the actuator mechanism just in case: the solenoid should give an audible and solid "click" when engaged. GONZO

GONZO.

 

[Dave Russell]

Hi Brian,
First the oil viscosity
A comparison of several oils. Gear oil viscosities are rated at 100 degrees F. Motor oil viscosities are rated at 210 degrees F.

SAE 5W-30 would have a viscosity of 90 SUS at 100 degrees & 35 SUS at 210 degrees

SAE 30, the originally recommended oil, would have a viscosity of 480 at 100 degrees & 65 at 210 degrees.

SAE 20W-50 would have a viscosity of 300 at 100 degrees, & 100 at 210 degrees.

RL MT-90 a 75W-90 gear oil, would have a viscosity of 200 SUS at 100 degrees, & 100 at 210 degrees.

Obviously, the transmission will hopefully be operating at somewhere between the two temperature/viscosity ratings. Your 5W-30 is much thinner than the originally suggested SAE 30. Leakage in the OD pump, accumulator, valves, & servos would likely result in too low operating pressures, especially at higher temperatures. Depends on th condition of the internal parts.

Many folks have good results with a non exotic SAE 20W-50 motor oil.

Any oil that contains friction modifiers such as some of the synthetics is likely to cause slippage of some of the internal parts. The transmission synchronizers require friction to work. The two OD clutches require friction to work.

MT-90 is preferred by some because it specifically does not have friction modifiers & gives more positive synchro & OD clutch operation.

Control valve adjustment
The control valve located under a brass cap near the front RH side of the OD must be correctly adjusted. Under the brass cap is a spring, a spring follower, a control ball, & a long operating rod. The ball should be 5/16 diameter. The ball lift is what controls shifting. The book method of putting a pin through the RH arm & adjusting the LH operating arm is not a very reliable method of setting the ball lift. Wear in any of the parts will change the required setting from the original pinned arm method.

The most accurate & reliable method of setting the valve lift is:
a- Set control valve ball lift to .030" to .040". Measure with dial indicator. Cap & spring removed. Adjust clamped operating arm. Verify movement with the solenoid plunger, not the arm. I machined an adaptor to fit snugly in the plug hole & to extend high enough to provide a flat surface for a dial depth gage to sit on. I made a cup shaped end for the gage so that it would easily center on the ball.

b- Set solenoid control arm (on solenoid plunger) to .160" drop. Adjust stop or add stop below the plunger if needed to accomplish this. (Arm drop is not the same as plunger drop due to slack in lifter.)

OD operate solenoid
a- The OD soleniod is designed with two electrical coils. The first coil (operate coil) is energized by the OD circuitry. It momentarily draws about 20 amps. As soon as the solenoid is operated, a contact on top of the solenoid opens & transfers current to the second (holding) coil which draws about two amps. If the switching contacts are dirty or damaged, the solenoid will be operating on the holding coil only & will not have enough power to engage the OD. The contacts are located under the top rubber boot.

b- If the switching contacts do not open due to contact problems or the solenoid travel not being adjusted to give a full soleniod stroke, the solenoid will remain energized by the operate coil & burn out quickly.
D

 

[Keoke]

Well You guys after you do all the good things Dave mentioned it also good to check the pressure in the system .Using an oil filled guage 0-to-1000 PSI attached via the operating valve plug hole using a spare plug modified to attach the guage, Pre BJ8 cars should build and hold ~450 PSI pressure. BJ8's should show 490-to-500 PSI.--Fwiw---Keoke

PS: Gonzo I too find MT90 not good in my OVD center shift box.

 

[BrianN]

Thanks, Dave for the oil explanation. I was sort of experimenting based on various bits of advice from local friends with these sort of overdrives.

I topped up the oil and today the OD engages in about 2 seconds. Usually it takes 5-8. I am usually reluctant to fill the trans to the very top mark for fear of overfilling, and leaking excessive oil into the clutch area. Especially not knowing whether the dip stick is fitting right. I was figuring the goofy plug material over time has given way a bit and allows the stick to drop in too far, giving a false reading. Maybe the top mark is accurate after all. Sunday I hope to go to San Ramon. It if is a hot day this will all test out in comparison to last week's drive.

And one further note: I am lucky that the "click test" always indicates good results. No apparent problems there.