MGB & GT Forum

Driving my GT with OD thru West Virginia. Before the trip, I filled the tranny with 20W50. OD great thru 1st 200 miles- when I got into the mountains. it slipped out a few tomes when I pressed the gas for more power. Does this sound normal? od engaging more slowly than earlier in the day.

Easy things first; recheck oil level with the car sitting level.

thanks!

Don,
Judging by your other posted, you may have some electrical gremlins at play.

Sounds like perhaps the oil pressure to the solenoid is low. Should be in the 400 psi range up to maybe 420. It will engage at lower pressure but without full pressure may not stay engaged. Rather than having it back out under load, I would suggest not using OD until you can check the transmission.


GMc

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Wait for me at the gate Tuffy, because without you they're never gonna let me in.

SDCH WTCH-X Twin Oaks Tuff Nutt
2008 - 2022

It can also be electrical on the OD inhibitor switch failing when climbing. I had this once with a working OD in descent. One check is pulling and pushing the gearshift slightly. Do know that slightly thicker 20W60 oil may be used instead of the specified 20W50. 80W90 is NOT to be used, since the pump mechanism may fail then. Of course a refurbish action on the O rings is another option and so is measuring the oil pressure with the proper tool..

Statistically spoken, the majority of OD problems are electrical, so solenoid and switch related. The mechanism as such is quite longliving because the Laycock unit was primarily dimensioned for Volvo's with much higher engine power levels than the MGB ever used over the years

PS I once renewed all O rings accessible with the OD in situ so all but the ones pushing the annulus. And in the end it had to do with a failing electrical contact of the earthing/mass side of the solenoid (indirectly solved by a single O ring renewal on the pedestal above this solenoid BTW)
This thicker O ring is lying near the topleft corner of the appended picture and it had both hardened and shrunk in thickness. I do not want to frighten you off, but this picture shows all the parts relevant to the OD, the solenoid itself, hanging on its connection in the B excepted. BTW: BMC/BL found it wise to position the bullit in the solenoid + connection to the inhibitorswitch so high up it is inaccessible for both loosening & re-attachment by hand!

In the same way IF the inhibitor switch is indeed the guilty one, access is almost impossible without dropping the gearbox/OD crossmember...
Some B owners rather cut a large hole in the gearbox tunnel instead (and close this off afterwards with a readymade coverplate). My MG mech once did without by combining both this X member action and opening up the gearbox tunnel from above (led to a lot of swearing by him)

PS2 The hotter the unit becomes the thinner the oil and engagement of the OD may become a bit slower and disengagement slightly more abrupt




Edited 5 time(s). Last edit at 2024-04-17 04:45 AM by Donthuis.

Thanks for lots of good advice! Got home fine, had too much fun!

Please post the final outcome once you solved your OD problem for good




Edited 1 time(s). Last edit at 2024-04-17 04:43 AM by Donthuis.