There have been many posts here on failure of the 240 A70/71 automatic transmission overdrive electrical circuit, some of them quite bitter and competitive - check the archives. I'm going to try to help some poor souls by writing to this board again, although I know the snipers lie in wait to abuse me again on this subject. By the way, if you doubt my mechanical bona fides, I'm a retired nuclear submariner and this little overdrive circuit issue is small crackers. I am not offering the Volvo mechanic's "by the book" answer to problems with this circuit, nor am I going to tell you how to "keep it original," or how to perform microsurgery on sealed relays. Instead, I am going to tell you how to fix your car, for good. I eliminated the mis-named "overdrive" electrical circuit on my car, completely, by altering the overdrive solenoid so that it ALWAYS allows operating fluid pressure to the 4th gear circuit in the transmission. My car is now a permanent 4-speed, all day, and it does not depend on the operation of an electrical circuit to give me 4 forward gears.


People write "help" messages here and on other boards reporting that their 240 tranny dropped from 4th gear into 3rd gear and will not shift into 4th gear anymore, or does so erratically, in and out of 4th. this is almost always a failure of the "overdrive" electrical circuit, which enables 4th gear. The "concept" behind this arrangement is butt-backwards of what you would normally expect. If you grew up with Laycock de Normanville overdrives on manual transmissions - on your TRs, your Austin Healeys, and your old Volvos, you think that "overdrive" means an upshift to a higher gear, like from 4th gear to overdrive 4th so you can cruise the interstate - your concept is that you energize a circuit by flipping a switch, which causes a solenoid to retract electro-mechanically, which operates by a lever a hydraulic valve in the overdrive unit, which engages by hydraulic pressure the epicyclic/planetary gears, which changes your final drive output from 1:1 to .7:1 - engine RPMs drop, car goes faster. Right? That's not how it works on a 240 A70/71 transmission. On the A70/71 when you flip the "overdrive" switch you force the transmission out of 4th gear back into 3rd gear and your engine whines, wound out, obviously needing another gear to sustain 65-70 mph or better. This is not "overdrive" - it is more like a second method of shifting into "passing gear" - like for hills, or for a sudden burst to pass a slow truck. I'm not sure why this was needed, because the kickdown function on my 240 transmissions (I have had 5 240s) has always worked perfectly well if I wanted to drop down to 3rd gear from 4th gear. Let's assume that Volvo knew what they were doing and had a good reason for doing this - even so, they could have set it up so that the transmission normally operated in 4-speed mode with the "overdrive" circuit de-energized, then the driver could energize an electrical circuit that would run from a switch through a relay to a solenoid and would cut out fluid to the 4th gear operating circuit inside the tranny and cause a shift back to 3rd. This way, failure of the electrical circuit would give you a default 4-speed transmission. But no, they set it up so that the existence of 4th gear depends on the "overdrive" circuit being energized, all the time, and you force-downshift to third by de-energizing that circuit. This way a failure of the "overdrive" electrical circuit gives you a default 3-speed transmission. No one wants that because everyone operates their A70 in 4-speed mode day-in / day-out, and that is why there are so many messages here about this circuit. It cripples your car for high-speed highway use when it fails. More rpms means more wear on everything turning in the engine.


Now, let's add that this butt-backwards electrical circuit includes a unique relay that sells for anywhere from $30.00 to $50.00, a switch at the top of the gearshift lever with wires that get stressed and frayed, and a solenoid that lists for over $200.00, and is hard to get at with the transmission still in the car, in a very filthy location (grit and hydraulics do not mix well - so you have to spend a lot of time cleaning before you remove the o/d solenoid). And lets add that this electrical circuit is energized all the time you are using your car - no wonder it wears out and parts of it fail!


As you will read elsewhere in here, many times the problem is the relay. You can get to it by removing the glovebox and looking to the left just behind the dash there. It is white. There are plenty of posts on these boards about fixing or replacing (or jumpering out) this relay. If you want to get real nit-picky, you can try opening the relay case and doing solder-surgery on this plastic relay. I had no idea about this when I first engaged this problem - the relay looked sealed to me, and the relay-solderer's guild condemned me as a buffoon. (This is a rough crowd here). One relay surgeon's post on this board even went so far as to include a gallery of close-up relay pictures, in different stages of disassembly and repair - like electrical porn. If you have a relay problem and want to keep this bogus electrical circuit alive, there is already plenty of advice on "doing" the relay. Another main cause of failure seems to be the wires from the o/d switch where they come out of the shift lever column - they can get frayed due to physical stress due to shifting motion. There are posts on this too. The problem could be a shorted or broken wire anywhere in the circuit. You know how to hunt for that. Finally, the problem could be the expensive overdrive solenoid - it could be failed open, shorted, or clogged with crap.


The solenoid mounts to a machined, flat, horizontal surface on the driver's side of the tranny with two 12mm bolts and it has one white wire. The case is the ground. There are two small holes in the machined flat surface, and transmission fluid under pressure passes from one hole to the other, or not, depending on the position of the solenoid. The at-rest, de-energized position of the solenoid prevents fluid from "communicating" between these two holes, disrupting the hydraulic circuit that "enables" 4th gear. Keep in mind that this hydraulic circuit does not CAUSE a shift to 4th gear when complete - all it does is ENABLE 4th gear - the transmission will shift into and out of 4th gear at appropriate speeds/conditions by other means. When the solenoid is energized, it creates an electro-magnet that sucks up the core "slug" against gravity and spring pressure - when this core slug is lifted it opens a channel that allows fluid to pass from one hole to the other - completing the hydraulic circuit, enabling 4th gear. When the solenoid is de-energized (slug in the down position), this hydraulic circuit through the lower part of the solenoid is closed, fluid flow is disrupted and 4th gear is disabled.


If your solenoid fails, or if you are just tired of chasing this backwards circuit, here is the permanent fix. Remove the solenoid. There are good posts on how to do this - get everything really clean first. I had to heat red-hot and bend a cheap 12mm wrench to get the right down-curve offset to remove the two 12mm bolts, without having to get better access by dropping the back end of the tranny a little by removing the center support. Take the solenoid to the workbench. Cut the white wire off, all the way flush with the solenoid top, as an expression of your vengeful frustration with this circuit. Remove the two o-rings (they will either be in the o-ring seal-tracks in the bottom of the solenoid, or stuck to the machined flat surface on the tranny - either way, get rid of them). You will see on the bottom, or "business end" of the solenoid a hole in the very center and a hole near the outer periphery. You want fluid to be able to pass from one of these to the other, so take a Dremel moto-tool with a very fine metal-cutting burr-style bit and route/cut a channel between the two holes. Try to keep this new fluid channel neat and not much larger than the diameter of the largest of the two holes. When finished, blow it off with compressed air, flush it with brake cleaner, etc. - clean all the crap off, metal, dirt, all of it. Put a new o-ring in the outer o-ring channel. I "tack" it in place with a little aviation permatex dotted into the channel in a few spots on a toothpick just to hold the o-ring. There are two ways to go with the inner o-ring - I have done both and both work: (1) leave it out altogether, or (2) slice a small section out of a new center o-ring, for the fluid channel you routed out with the Dremel tool, and tack the resulting "C"-ring (ha ha) in place with aviation permatex, making sure that the open section in the sliced o-ring lines up with your fluid channel. Let the permatex have a few minutes to set so the o-rings won't fall out when you turn the solenoid upside down to mount it. Lay your jimmied solenoid onto the machined surface on the transmission carefully and bolt it down. Now your brick has a 4-speed transmission again, all the time, and the whole o/d electrical circuit is irrelevant - no more soldering of relays. If you want passing gear, kick it down and it will give you third without having to flip a switch on the shift head. I have two cars with this fix on them now, and I have two more 240s (family, with kids) that will get it as soon as their o/d circuits act up.


I hope this helps some regular Joe fix his car and get rid of a headache permanently. Meanwhile, I am ready now for the army of hecklers who haunt this board to start attacking me for every conceivable reason. I think there must be some secret code that I do not know that lets you post here without being savaged by "the regulars." Bring it on, gentlemen.


RDS

I've never replied to such an old post, but had to because it's sooo.... GOOD! Thank you for explaining the backwards Volvo thinking for both naming it an overdrive, and for having it powered when in 4th gear - which does sound crazy. I just repaired the frayed/destroyed/shorting white wire from the unit on my 240, and it works fine now (hard as hell to get to, but... persistence...), but I also have the bypass from IPD as a future back-up, when needed, and an extra relay if that's a future problem. Nice to confirm that just removing the wiring would NOT have helped - would have kept in 3rd gear forever. Thanks for the great post.

The overdrive on my 1990 240 Wagon quit working and the dash light came on. I checked the gear shift wiring, per Mr. Bernstein's instructions, no joy. I replaced the relay, again no joy. I ordered a new solenoid via ebay and set about installing it. The solenoid was fairly easy to get to but the wiring connector to the gear shift wire was impossible to reach. I ended up cutting the existing wire and the new wire where both were accessible and spliced
them together with compression connectors. Before doing the connection I slipped some heat shrink tubing over the cable. After doing the connection I coated the connector with dielectric grease, slid the heat shrink over the connector then filled each end of the tubing with more grease. Using a heat gun I shrank the tubing. Thus a waterproof connection and a working overdrive.

Roger, There are many great things in life.But I have to say, your solution to the 240 "overdrive" issue ranks in my top 10. What a sweet little fix your instructions led me through.
The most difficult part of the fix believe it or not was finding a replacement o ring. I was going to attempt the manly melt and bend a wrench method to get to the 2 bolts. But I find buying a 12mm GearWrench so much more elegant.
So, I thank you for your post. To hear my 1993 240 drop into 4th was priceless...

yay me!
I was able to access the solenoid bolts with a shot extender and a flex head ratchet.
once i broke the bolt with a little PBBlaster removal was a cinch.
A Dremel 426 Fiberglass Reinforced Cut-off wheel made cutting the groove a breeze.
The longest part was trying to clean clean clean.

All Hail Brickboard!

Roger, you are a f*@#ing genius.

I was having an intermittent problem with my 1992 Volvo 240 DL not switching into 4th gear. I paid $100 for a transmission flush + $30 for a kick-down cable adjustment which made it work again for a couple of weeks, but one day, after work (which was a warm sunny day) it failed again. When I called the mechanic to report the problem happening again, he said that the it must be the transmission and that it needed to be replaced with a rebuilt one to the tune of $775.

(Here's a note: Adjusting the kick-down cable isn't going to do anything if it isn't stuck (springs back freely), it isn't hanging slack, and it engages when you step on the accelerator all the way (you can feel it when you step on the gas pedal at the very end of the stroke - it's a "click" feeling, not a sound). All the kick-down cable does is bring the car down into third gear as a "passing gear" to get past other cars on the highway when you stomp on the gas. If it feels / seems to be working correctly, it's probably not that.)

So, I figured I may as well try Roger's fix before I replaced the damn transmission anyway.

First, I wanted to eliminate all the other possible problems. I checked the voltages on the relay switch behind the glovebox with a voltmeter in accordance with this other post on another forum: http://www.thevolvoforums.com/volvo-240/8789-1992-240-no-fourth-gear.html I didn't get any big voltage drops when I switched the overdrive on and off so the switch seemed ok with these readings:

Pin 31 - Ground
Pin 15 - 11.89V when on; 11.81V when off
Pin 87a - 1mV when on (the arrow lit up on the dash); 11.81V when off
Pin 87 - 0.9V when on; 11.81V when off
Pin 86 - 0v when on; 0V when off (the meter would jump when I hit the switch, but would settle back to 0 after a couple of seconds)

Then, I checked the arrow light on the dash and it turned on and off every time without fail.

Finally, I lifted the car and checked the wire coming from the shifter and going to the solenoid - it looked in decent shape.

The next thing I did was get under the car and got my head close to the solenoid and had my wife push the overdrive switch a few times and listened. The solenoid was definitely clicking, but it was much louder when the overdrive would engage (the arrow would light up on the dash). Since my problem was intermittent, it could have been working this time and not others, but I had a suspicion (because of the difference in the volume of the clicks) that the solenoid wasn't opening fully.

I decided to pull the sucker out and have a closer look. I had to buy a seriously angled box wrench to get at the solenoid bolts - which I found at the local auto parts for $7.99 - and went to work. I bought some brake cleaner and a wire brush for $4 total and did my best to clean out the area before I pulled out the solenoid.

NOTE: The cap on the solenoid DOES NOT COME OFF, so don't try to pry it off with a screwdriver. The cable is part of the assembly and has to come out with the solenoid.

After disconnecting the connector on the other side of the transmission and removing the two cable clips I carefully pulled the thing out being careful to not get any gunk in the holes. The o-rings stayed stuck on the transmission, so I carefully(!) pulled them both out, too.

I took some alligator clips and connected the chassis of the solenoid to the negative on the battery and connected the other clip to the solenoid wire. I tapped this clip on the positive terminal of the battery and I could hear/see the little piston inside the solenoid moving. It seemed to work ok, but I am so fed up with this problem that I decided to move ahead with Roger's fix.

Here is a picture of the original solenoid (no alterations): http://www.omargarciaportfolio.com/Solenoid/SolenoidUntouched.JPG

I used a Dremel with a metal burring tip to "connect" the holes and the result looked like this (after cleaning with brake cleaner, wire brush, compressed air and a paper towel):
http://www.omargarciaportfolio.com/Solenoid/SolenoidRouted1.JPG
http://www.omargarciaportfolio.com/Solenoid/SolenoidRouted2.JPG
http://www.omargarciaportfolio.com/Solenoid/SolenoidRouted3.JPG
http://www.omargarciaportfolio.com/Solenoid/SolenoidRouted4.JPG
http://www.omargarciaportfolio.com/Solenoid/SolenoidRouted5.JPG

I cleaned everything and put the big (outer) o-ring back in (it was in good shape and stayed in place nicely) and I decided to not use the small o-ring at all again and stuck it my toolbox.

I carefully(!!!) cleaned the area on the transmission one more time before remounting the solenoid and bolted it down. I reconnected the cable (although it does nothing now) just so that everything was where it should be.

I took her out for a highway drive and, lo and behold, in and out of 4th gear like a champ!! I noticed that it switched a little later (at 50 MPH vs. 45 MPH before the fix), but that's no problem for me.

I must admit, I was reluctant to do this fix until I found this:
http://www.ipdusa.com/products/4793/110397-automatic-over-drive-solenoid-bypass-kit

IPD is selling THE EXACT SAME FIX for $39.95! It is just a cap with a channel routed in to permanently connect the two holes in the solenoid.

Summary: if you aren't worried about towing heavy trailers or driving up and down mountains, you can disable the solenoid with Roger's fix above. You can do it in two ways: buy the IPD Overdrive Solenoid Bypass Kit for $40 or route it out yourself. If you are having problems with 4th gear and have checked everything else in the overdrive circuit, your solenoid is probably bad anyway, so there's no point in saving it - you'll have to buy a replacement at some point if you want the "overdrive" feature.

In any case, my problem seems to be solved - I'll post back in a few weeks to confirm the repair. But if the problem keeps happening, I'm may have to cough up the big bucks.

I just went through the same problem with my '89 240 and my Volvo mechanic did the router method as described. Only problem is it didn't work. Car still won't go into 4th. I don't have a tach and am wondering how many rpms I'm turning at 60mph in 3rd. Anyone? I know 3rd is 1:1 but it sure sounds like the motor is winding, especially with a 3:31 rear end. I don't think the car is worth replacing the tranny so I may drive it as is. I've got 230,000 miles and the motor runs great but I wonder how long it will last if I don't go over 60mph in 3rd.

If you do not want to fix the problem--that's ok. Stop worrying about it. You'll burn more gas than you would having the overdirve available but you will not wear out the engine. At 60 mph your doing less than 3,000 rpm in 3rd with a 3.31 rear. It may sound busy but if it could, your motor would be laughing at you for the worry. Just drive on. -- Dave

Roger:

I just read your post on the "insane" Volvo OD circuit. I have been attempting to fix one of our 240's OD problem for some time now.

About one year ago I drove my daughters '89 244 and noted it was at high revs so I checked out the OD relay and it was working. I then got underside and noted that the OD solinoid was crushed by the shift linkage which had dropped down 1/2 to 3/4 in. caused by the failure of the nylon shift linkage bushing. The OD relay was toast. It was 5 above zero but I had to try to replace it outside. I did the best I could to clean the area and get the old one off. I did and managed to get a new one on. The problem with the trans not going into 4th still persisted. The single white wire comming from the shifter housing (neutral start switch) was deteriorated so I cut in a new wire and spliced it into the wire (difficult not much room to work) from the top inside the shifter housing and ran it to the male connector from the OD solinoid. Still does not work.

After several attempts and more failure, we only use the car for short trips under 40mph. Crazy, but I am frustrated as I do not know how to get to the connectors and wiring harness inside the shifter housing.

Perhaps the new OD solinoid is not working. Would it be OK if I put a 12v 8A fused line from the battery to the male input wire of the OD solioid to check if it engergizes with a click. Then I would know that it is the wire that is bad for sure.

Appreciate any suggestions.

Thanks,

Allan

Allan -- What you propose is just what the Bentley manual suggests for troubleshooting. If the OD solenoid clicks with 12V applied to its connector, it is OK (it grounds to the trans housing). Then, check the female connector (back up to the shifter box) for 12V to ground while a helper cycles the OD button on the shift handle. If NO voltage, the problem is upstream in the wiring/ OD relay/ fuse.

Jim

I'm a regular. I have spent countless, probably well over 1000 hours on this board, just to have some OTHER regulars continually nitpick my (factual and correct) posts. There's always someone out there who has nothing else to do but tactlessly try to get their little digs in. Best of luck to them... I've got other things to accomplish. The funniest thing is that the same people who have emailed me asking for help, turn around and post some ridiculous attempt at proving me wrong (usually because of the syntax of my post, or some dumb loophole that they'd have seen if they just read the post well).

Which is another reason that I took a big, long break from this place. Totally thankless people who demand help one minute and then shove it up your ass the next.

But that aside, I can say that your writeup:

1. Was thorough
2. Was factual
3. Offered an alternative design for the system for a fail-safe 4sp automatic.
4. Shows that you put quality time and thought into writing it.
5. Speaks from experience

So, for those reasons, my opinion is that this post is worth making the FAQs.

And if you do get heckled, I've realized, it is merely a fact of life here. I know my mechanical skill, you know your mechanical skill, and if someone wants to one-up me or one-up you, then that's what is going to make them happy.

The overdrive circuit is very silly the way it is designed. Who knows what kind of abortions occurred in the design stages. I suspect more than one.

At any rate, your post was a good read, and hopefully it will find it's way to the archives. Whether it is good practice or not is for the individual to decide.

Strangely, with ALL of the miles I've driven, I have never had an OD solenoid or relay problem in any of my Volvos. I don't understand it, but it's true. I've fixed a lot of customer problems with the circuitry, but never had any of them myself. (And with that, I'm sure my OD is going to stop working tomorrow morning.)

What a post, this should definitely be added to the FAQs. I doubt that there will be too many heckles, ignore them. You lay it out plain enough for my dog to understand.
I did the dremel modification for the first time 10 years ago after getting a car that had been "worked" on for this problem and royally screwed up by three different "mechanics". I eventually repaired the damage that was done and returned car to its' "proper" state just because I had the time to do it.I agree that the way this circuit is designed is ignorant and bassakwards, to say the least. This is a simple EFFECTIVE "fix" that cuts out the BS and can get you back on the road with all four speeds. Thanks. Later,rcs

RDS- Just ingore the hekklers. Some just want to be top dogs.

Very nice post. Well described beyond the need for any hydraulic "porn" for those not yet intimate with the solenoid. A valuable contribution.