My Overdrive just DIED

[spineguru]

On the way home today, my overdrive died. I had switched it off to stop at a light. the next time I went to switch it on, nothing.

With the car off but the key on, I can hear a "clicking" behind the dash when I flip the switch on and off, so something is working.

I am going to try to look under the car for something obvious, but I am TOTALLY unfamiliar with this. Anybody hazard a guess what has happened? It was literally working fine just moments before and then it was completely gone! /ubbthreads/images/graemlins/cryin.gif

 

[Don Elliott]

The clicking you hear from under the dashboard is the overdrive relay and the fact that it's clicking tells you that it's OK - at least to there. The relay is normally located under the dash - attached to the lower left corner of the battery box.

Do you by any chance have loose carpets where your heel can slide the carpet back and forth ( like when you braked for that stop and then put the other foot on the clutch) and maybe you disconnected the wire connection to the overdrive. It has happened several times to me. If these connections are all pushed in securely and no wires are broken under the carpet, it could be that the solenoid which is located on the left side of the overdrive is defective.

I cut a hole about 3" diameter near the solenoid with two smaller holes higher up on the steel tunnel wall. I can lift the carpet, pull out 3 rubber plugs, and with a long screwdriver from above I can unscrew the 2 screws holding the solenoid. Then I can lift the solenoid out through the large hole. Here I use a rubber hole plug that is the same size as the one used in the floors for access to the jacking points. I can change a solenoid in 15 minutes this way and don't have to work blind in the dark under the car.

https://mysite.wanadoo-members.co.uk/trebor/don3a_big.JPG

 

[TR4nut]

I'm not adding much to Don's very good advice at this point. But before you get too worried, try to see if the solenoid is engaging. I think you could put it in third or fourth gear, have the key on and do the same test. In addition to the relay making a noise, the solenoid will make a sound. On my TR4, I hear both the electrical relay noise, and also a pretty loud click from the solenoid. Best way would be visual confirmation. Solenoid failure I believe is one of the more common ailments on the A-overdrive. If it does turn out to be the problem, BPNorthwest looks to have the cheapest supply right now at around $80.

Randy

 

[spineguru]

I checked it out and looks like the solenoid is the problem. There is no click down there, anyway. Unfortunately, I don't have the cool little hole setup that Don mentioned, so I jacked up the car and got under there and had a friend flip the switch. We could hear the relay click, but nothing back by the gearbox. I really don't have a good setup for working on stuff on the underside of my car, so I may have my trusty mechanic take a look. He is usually pretty good and will at least verify the problem for free. Thanks for the quick responses!

 

[TR4nut]

Glad to hear that it sounds like something that can be fixed easily. Go with Don's advice first and check that circuit to the solenoid - it could be an unplugged wire, or possibly even a bad lockout swith on the transmission (I think 3's had these, my 4 does for sure). Any of that is even cheaper than the solenoid.

Randy

 

[myspitfire]

My guess when it happened to my OD(J TYPE)it turned out to be a loose wiring connection(spade type)at the selenoid.,That clicking is normal when you hear that the electrics are trying push the selsnoid plunger,Most likely a ground connection.
Ken
79/80 Spit 1500

 

[vagt6]

A significant percentage of OD problems are related to the solenoid. Check the wiring, as mentioned above, then check the solenoid.

But first, check your gearbox oil! That's the easiest diagnostic. If it's really low, you may have a leaky seal.

Good luck, let us know . . .

 

[TRTEL]

Bryan, If it does appear to be the solenoid, do not immediately order a replacement. The original Lucas units were, believe or not, really bullet proof. The only real problem we found with 9 out of 10 were dirty contacts. The old lucas ones used to have a crimped band around the base of the boot on the top of the unit. Carefully take some pliers and gently twist it back and forth till you break it off. Slip the boot up until you can access the contacts. Take some very fine wet/dry sandpaper, about 320 grit. Remember to clean both sides of the contacts. I usually fold a strip over and do both sides simultaneously. Don't get carried away unless they look really pitted. They're silver and fairly soft. Then rinse them off with some isopropyl or methyl alcohol with a dropper. Don't use a cloth for drying the lint can cause no end of grief. Then bench test using the actuator plunger. BE CAUTIOUS you must use the plunger because as it is pulled up by the field it then breaks the primary circuit and is then held in place by the weaker secondary. If you're just checking continuity don't leave the circuit closed for very long as the primary draws several amps and can burn out that coil. In practice this can actually be the reason for a true failure. Usually because of dirt or corrosion getting up in the plunger/actuator bore keeping it from moving up all the way. Which is also a hint to clean those areas as well. The cleaning procedure also works for the relay as well, they too rarely 'burn out'. Just flatten the crimps in the aluminum can and pull it off the phenolic circuit board. The switches on the gearbox top unfortunately are steel and are not practical to dismantle. Other contacts on the cars you can service the same way are in voltage regulator and the horns. Have fun.

Tom Lains
TS8651
TS58107

 

[TRTEL]

OOps, Forgot to add make sure to reseal the boot with some rubber cement, silicone, or something similar.
T. Lains

 

[bigbadbluetr6]

Hey Bryan,
Tom is right. I had the same problem with my overdrive after using the overdrive a few times then the next time I tried to use it I got nothing. After checking all the wire connections my dad and I cleaned up the contacts and it has worked everytime I have flipped the switch. Good luck to you and keep motoring.

 

[spineguru]

Update:

I finally got around to swinging by my mechanics shop and as I expected, he was nice enough to jack it up and look at it for free. As I had mentioned, the focus quickly went to the solenoid. Just when I thought he was going to say it was bad, he literally "tapped" on it with a wrench and it started working! Turns out it was just stuck. He spent a little time cleaning it up and making sure everything was moving again (not exactly sure what he was doing under there), and it seems the problem is fixed for now. I had to run so I wasn't able to leave the car there and I was certainly happy for the free service, but next time I have the car in for something else, I may have him spend a little more time making sure it won't freeze up again.

Sometimes things DO work out. /ubbthreads/images/graemlins/laugh.gif

 

[Don Elliott]

Lets hope it was only that. See the attachment of what I did for quick access to my solenoid. The rubber plug lower down is the same as for the floor and I can unscrew the solenoid screws using a long skinny screwdriver through the other holes.

 

[sammyb]

I just want to point out that Don probably has the cleanest trans cover, floor and solenoid I've ever seen! Do they not have any dirt on the roads in Montreal anymore?