Overdrive Help 3 & 4 Gear selector switch faulty?

[Andrew1]

Hi Gang and thank you so much for all your help! I tried to add my two cents on a solution for removing ceased A-arm bushings... I know a sawsall sounds drastic, but it worked well and I added it the recent bushing posting if you are interested.

Onto the next issue. The overdrive on a BJ8 has been overhauled mechanically, and I've experienced intermitant shifting in and out of overdrive at highway speeds in third gear only. Fourth gear overdirve operation is fine.

Further diagnostics revealed that the Solinoid was bouncing in an out of activation by slight movements in the normal play of 3rd gear. It appears that the switch that "detects" 3 & 4th may be faulty or misadjusted.

Actually it's sorta cool operating the Overdrive with slight flicks of the gearshift..... like a 60's version of Tiptronic!!!

Before I take off the transmission cover for the 10th time this season and for potential part ordering efficiency I'd like to get the feedback or experiences of those that might have had similar issues, specifcally;

1) Can the existing switch be adjusted?
2) If it has to be replaced, what is the Moss part number (the illustrations descriptions are not very clear in their catalogue)?

Thanks again as always!

- Andrew -

 

[Keoke]

HI Andrew, Yes the OVD switch on the gear box gear lever extension is adjustable.So is the Throttle sw. Be sure the throttle sw remains closed for~ 20% of the gas pedal travel.Also look at the OVD sw on the gear lever extension.If it has been improperly set up it is possible that the anvil it rides on has damaged the aluminum housing which traps the ball actuator in the switch barrel.There are two SW types: 1} has screw terminals Part No;141-100 and 2} Has Lucar terminals Part No;140-470, Additionally you may need the SW adjusting washer Part # 324-145---Fwiw---Keoke

 

[Dave Russell]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Hi Andrew,
I agree with Keoke. The most likely problem is that the 3-4 switch is not set quite close enough to the internal shifter mechanism. The adjustment involves setting the switch a bit closer (screwed in deeper) by using a thinner washer between the gearbox case & the switch. Almost any washer or combination will work.

I would start with something about .020" thinner than the existing one. It's pretty easy to check continuity across the switch terminals (wires removed) & adjust the washer thickness as required to get positive switch closing with the lever in the 3 & 4 position. Don't move the switch any closer than just enough to make the switch work.
D

 

[vette]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Hi Andrew, It could well be an electrcal issue with the O/D as the previous contributors have talked about. They do have alot of experience. But my O/D also drops out once in a while, while cruising in high gear, at lower speeds, with light throttle. It has been suggested to me (on this forum as well) to check the transmission oil level, and to clean the strainer screen mounted in the O/D unit. My oil has maintained good level, but I have not cleaned the strainer as yet. Just thought it might be something else to check.
/ubbthreads/images/graemlins/cheers.gif Dave.

 

[Dave Russell]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Hi Vette,
Since the OD pump is operated from the OD tailshaft, & it is turning relative slowly at lower speeds, dropping out would be a sign of low oil pressure in the OD. Provided that the OD solenoid is not dropping out. There could be many reasons for this. Your suggestions are a good place to start. Using a slightly higher viscosity oil might help if the oil pump or the accumulator is worn. Check first to see if the OD solenoid is staying put. Transmission cover removed. Don't get your shirt tail caught in the propellor shaft. This will tell you if it is an electrical or hydraulic problem.
D

 

[golf]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Hi Andrew,I experienced the exact symptoms.However all of my attempts to adjust the switch you mentioned did not totally stop the problem.I have a habit of holding on to the gear shift while driving and found that I could shift in and out of overdrive with the slightest movement of the gear knob.I finally gave up and ordered the switch#140-470 from Moss.Now the overdrive stays in.This is a very important switch to guard against damage to your overdrive while backing up,so always make sure it works properly.Good luck,Ben

 

[vette]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Thanks Dave, I do have to get around to cleaning the strainer and doing some diagnostics on this situation, but It has happened so very few times and I am enjoying the week-end outing so very much that I just keep driving it. I did repack my front wheel bearings last week though, and put another 200 miles on the Healey today. Just got back. I have some other project cars I'm working on for other people and 'my' cars just get the minimum maintenance to keep them going. Thanks for the help.

 

[Andrew1]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Andrew here and the problem has been fixed as per the feedback from Keoke and Dave. Thank you as well as the other contributors too!

There was two spacing washers installed and a quick removal of one washer plus a cleanup of the lucar terminal switch and the gear seletor anvil allowed the switch to close properly.

I noted too that the switch button had developed a slight pit from the years of use in the same spot, however I decided to simply spin the button 45 degrees and allow it to brush against the fresh metal..... if all thing go to plan I can keep rotating the switch button for another 60 years until I have to replace the switch ! haha

 

[Giovanni59]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Hi, I am not as technically knowledgable as you guys but I am experiencing a similar problem. I have a 1958 100-6. After driving at 60-70 mph for 5 to 10 minutes the overdrive starts turning off and then on. This happens when I am in 4 th gear. Is it an adjustment problem like you guys have been discussing?
Thanks
John

 

[Dave Russell]

Re: Overdrive Help 3 & 4 Gear selector switch fau

Hi John,
If wiggling the shifter has no effect on the problem it is not likely to be the switch. See my answer to Vette above re: oil pressure.
D

 

[anthony7777]

Re: Overdrive Help 3 & 4 Gear selector switch fau

i also had intermitant operation of my overdrive,on and off as it pleased.i found that a wire on the "overdrive"dash switch was warn through just at the connecting point it was bouncing in and out of contact with the switch,removed switch-clean and reinstalled wire,result-less r,p,m's-more go!