View Full Version : Overdrive question - electrical

03-14-2008, 07:51 AM
Installed an A type and it is work great. My problem is when I decelerate it disengages the overdrive.
At first I thought low fluid. So I added some more and checked the level. It was fine. After driving a while and testing the system by engaging and decelerating, I heard the solenoid kick out. I figured it must be a current draw causing the engagement solenoid to open.
Do you have any suggestions on what area of the fuse holder would be best for the solenoid wire? Perhaps directly to the battery. Perhaps I'm not looking at the right place.

Any help would be appreciated.

Geo Hahn
03-14-2008, 09:33 AM
It might be the current draw you describe but it takes so little to hold that solenoid (compared to the current to throw it) that this seems unlikely to me.

Another area to check may be the adjustment of the arm operated by the solenoid.

I know mine will sometimes disengage if I hit a rough area of road at high speed -- perhaps the jolt of deceleration is affecting it?

03-14-2008, 09:44 AM
Check the ground. We had a problem with the OD in the Volvo and it turned out to be the ground connection had worked itself loose.

From what I understand, the A & D type overdrive solenoids draw more current when in use than the later J-type. In Volvos the earlier cars with the D-types run the solenoid circuit through a relay whereas later J-type solenoids are wired directly: power to column switch to lock out switch to solenoid.

03-14-2008, 10:03 AM
Thanks guys,

I think it has to be electrical because I can hear the solenoid cycle and it engages and disengages based on deceleration. May be the ground wire. WIll have to check it today.
If it isn't the ground I may run the solenoid power wire diractly to the battery terminal.

03-14-2008, 11:36 AM
Check that the arm is adjusted correctly. There are evidently two coils in the solonoid, and when the pull in coil engages, and the solonoid reaches full travel, there is an internal switch that changes to the hold coil, with a greatly reduced current draw. If it does not do this, the solonoid will overheat, and eventually fail. Second, I would check the lock out switches.They are adjusted with shims, and one (or more) may just barely be engaged. When the "load" shifts as you decelerate it may move the shift fork and rod just enough to trip the switch. I had a 3A through here recently where the shift housing had worn enough that the switch would only work in 4th gear. The owner did not choose to pursue the problem so I am not exactly sure, but either wear or a slightly bent rod was causing it.On that car, I ran a lead from the fusebox to the relay for power, and just brought it through where the harness grommet was. No big thing, plenty of power, and fused to boot. If you have the "standard" OD wiring, don't forget to check the bullet connectors where the two parts of the harness join. Movement of the trans on the mounts could be disturbing a connection there. Hope this helps a little.

Don Elliott
03-14-2008, 12:31 PM
I had trouble similar to yours. I found the answer. The wire connecror, bullet (bayonet) type, protected by an insulated sheath were located under the carpet on the driver's side. Every time I slid my foot to clutch or de-clutch, the carpet slid about an inch and the connector was breaking and re-making.

03-29-2008, 05:46 PM
Guys, I think the problem is the switch mounted in the top of the transmission for third gear. When ever I'm in third and let off the throttle the OD disengages. If I push on the shift lever the OD engages. I think the switch needs to be reshimmed for proper gap.
What I think is happening is the fork is pushing one direction during aceleration and when I decelerate it is pushed in slightly the other direction thus moving the brass rod slightly.
Any comments?

03-30-2008, 07:14 AM
What I think is happening is the fork is pushing one direction during aceleration and when I decelerate it is pushed in slightly the other direction thus moving the brass rod slightly.
Any comments?

It pretty much has to be something in the interrupter switch, if you can get it to work by wiggling the gear shifter. You could try turning the ign on with o/d switch 'in', and try selecting third/moving the lever around and listening for the solenoid actuation. IIRC it is one switch for both 3rd and 4th; in which case if it is OK in 4th it is more likely to be something in the actuation than bad contacts in the switch itself..(?) Pete

03-30-2008, 10:14 AM
Perhaps I'm just reiterating your comment.
When I changed over from TR3 tranny to TR4 and added the OD parts and unit. I had to drill and tap the holes in the linkage cover. If you look into the hole there is a brass plate that trips the switch when the linkage is moved. There is one plare for third and one for forth. I think the third gear plate is lower then the forth gear plate thus allowing the unit to drop out only in third gear. When I move the selector forward or back it may move the plate to a point of making the switch or breaking the switch.
Follow my logic?

03-30-2008, 12:39 PM
I follow your logic Larry, and it seems possible to me. ISTR it was Nelson Riedel that measured and found that the location of the hole for the switch was fairly critical. Have you tried removing the shims under the switch ?

But, I wouldn't want to go very far assuming that is the problem, just because it's logical. I've seen way too many electrical problems that seemed related to odd things, just because of bad connections somewhere. Had one for awhile on the Stag where it would drop out going uphill; turned out to be that one of the connectors on the solenoid wasn't quite tight and wouldn't make contact under some conditions. That was just a few hundred miles after the problem where the engine wouldn't accelerate uphill, because of a broken wire near the starter solenoid that was touching something only during uphill acceleration.

Or maybe the switch likes being pushed sideways in one direction and not the other ? Could be almost anything, so my suggestion remains to wire up a test lamp to divide and conquer until you isolate the problem.

BTW, those "plates" are both part of the same 3-4 shift fork.

03-30-2008, 03:47 PM

I am going to wire in a light to the ground wire to see what happens during a drive. I think it will show my logic is correct.
As for hole location, I think I very close to center.

Haven't removed the shims yet, again too much work just to try. Need to do the test light first.

Thanks all...
Randall you amaze me. You must be on this sight a lot during the day. You are a wealth of good knowledge, I appreciate you.


03-30-2008, 05:48 PM
Good discussion.I've had suggestions relating to whether to clutch or not to clutch switching on the OD,My QUESTION to the group WHATS PROPER?...Doesn't switching on(OR off) the OD wear on the crank END PLAY?I have a correct funtioning J-Type. Thanks
(or better yet whats the factory shop manuals say)

03-30-2008, 07:20 PM
I've had suggestions relating to whether to clutch or not to clutch switching on the OD,My QUESTION to the group WHATS PROPER?Well, John Esposito is on record as saying one should always use the main clutch when shifting the OD.

OTOH, the factory workshop manual for my Stag (3.0 SOHC V8 in front of a J-type) says the unit is designed to handle full-throttle shifting and specifically mentions "clutchless" shifting. Plus the factory owner's manual for my TR3A (2.0 L4 in front of an A-type) doesn't mention any need to use the main clutch when shifting the OD (although it also doesn't mention using it to shift the main gearbox either <g>).

So, what I do is use the main clutch any time I'm just casually changing gears, but not when I'm shifting with the throttle wide open (which rarely happens with the Stag, since I also usually drop to 3rd gear to pass someone).<div class="ubbcode-block"><div class="ubbcode-header">Quote:] ...Doesn't switching on(OR off) the OD wear on the crank END PLAY?[/QUOTE]I don't see why it would. The OD doesn't put any thrust on the crankshaft like the main clutch does, but instead has it's own thrust washers and bearings.

03-30-2008, 08:14 PM
GREAT information.That substantiats(sp)(what i've heard)But didn't know it didn't hurt the crank end play(on a jtype)But in the end its logical the LESS you clutch the better.I also have other habits of starting with clutchout &amp; utilizing the brakes instead of downshifting alot.,which i think ALL helps with a longer engine life.Paying CLOSER attention ALL started after the engine rebuild.BEFORE THAT old habits prevailed.

03-30-2008, 10:59 PM
Ken i usually just back of the throttle a bit(take the load off ) and flip the switch at the same time going up and just flip for downshift. A little practice and ya get pretty good at it.