Overdrive Problems

[Scot]

I have never had a problem with my BJ8 overdrive until yesterday.
It seems it engages when I throw the switch about half the time and then when it does engage it comes out of it quickly uncommanded. Lots of RPM changes and jerking going on when switch is in overdrive.! This happens in both 3rd and 4th gears under no load. Will not work at all with accelerator pedal depression when switch is engaged.
Could this be a relay or a solenoid problem? Thanks for any help....

 

[Coastalman]

I had a similar problem a few years ago and it turned out to be the relay.
Charlie

 

[Bob_Spidell]

I had a similar problem a few years ago and it turned out to be the relay.
Charlie

Same here. If you're careful, you can bend the tabs back and open up the relay to have a look (make a note of the connections first). If the points are worn/burnt you've likely found the problem. File and clean the points--same way you'd file ignition points--and put it back together; if it works you know for sure.

Had to do this on a road trip a few years ago. Repaired this way it should be good for thousands of miles--depending on how much 'meat' is left on the points--but I replaced mine when I got home anyway.

 

[Scot]

Thanks guys, I'm glad it's just not my imagination in addition to being an easy fix! The car was restored in about 1990 and the relay may go back much further than that. I know where the throttle switch is but not the relay.
Any idea what the service life of these things are?

 

[TimK]

It should be next to the thottle switch on the right side (I have a BN7). The relay has three wire connection tabs on top and one on the bottom.

It is in the upper left of this photo where I have installed a red wire inline fuse to the overdrive solenoid (white wire).

The service life on my OD relay is 51 years and over 100,000 miles and still working fine.

 

[KCC]

I had this problem a couple of years ago on my BJ8 and it turned out to be a faulty switch - some replacements are less than perfect. In my case I switched the overdrive swicth and the panel light switch to test and the problem disappeared

 

[Scot]

Thanks for the photo TimK and all the other responses. Nothing found yet but will keep you guys in the loop when I discover the problem...

 

[bighealeysource]

Hey Scot,
Might check out the solenoid as well although it obviously works or you would not be engaging the O/D at all. But could be about to fail and the electrics are shot. Plus something that I missed last year and turned out to be so simple it was embarrassing. Make sure your O/D/tranny oil is full and not just on the cusp of being low which might account for low O/D oil hydraulic pressure and maybe allow it to go in and out of gear. If you do find out you need an new O/D relay switch there is a Jag guy on ebay that sells them for $39.99 plus minor shipping which is far, far less than Moss or VB. If you need his ebay info let me know. Good luck with your trouble shooting.
Mike

 

[Scot]

Mike, Good call! I did check the oil level and just the tip of that dipstick broke off before I got the car. It does show the oil level however just above the low mark! Could that be causing the overdrive to fade in and out? I will add some and test drive...now that IS embarrassing!
Thanks for the tip on the relay.

 

[daily]

howdy,
i've had similar o.d.itis
solution,replace lock out switch on trans side cover.
the detent ball wears [prematurely c/o moss motors 1.5 yrs]
allowing switch to ''bounce'' hence eratic operation
confirm switch integrity by engaging o.d. panel switch,
-place lever in high gear move lever sideways,listen for
solinoid activation,if it trips the lock out is bad.

as far as low gear oil is concerned, i am also experienced,
due to prior neglect be for warned,i had to replace o.d. pump
due to low oil, it galded-eroded the plunger wheel until contact
with main shaft cam was minimal i.e. no pump function.

with respect 59er

 

[Scot]

Update: Must have been the points on the relay or some other connector. I took apart the overdrive relay and cleaned/sanded the points and all other o'drive electrial connections. Also topped off the oil in the gearbox. Working buttery smooth like it used to! Thanks to all again....