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 litle 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 transimissions - 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 outpurt 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 transimission. 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 oprates 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 elecrical circuit incldues 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 transmisson 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 transmisson 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 (big famly, 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

Did the O/D selenoid bypass and it worked like a charm. Thank you for posting this. The instructions were great and very accurate.

Would this work on a 740? This sounds like it might be the solution to my problem - stopped going into high gear, but works fine in the first three...

Same transmission in later 740s, same solenoid... same fix.
87 or earlier NA cars may have a different trans, and the shifter shows "4321" instead of "D21" with a button on the side. IF it's 88 or newer, this is a sure thing.
--
Rob Bareiss, New London CT ::: '87 244DL/M47- 225K, 88 744GLE- 209K, 91 244 183K. Also responsible for the care and feeding of: 88 745GLE, 229K, 88 244GL, 146K, 87 244DL, 235K, 88 245DL, 236K

Thanks Roger for taking the time to post this excellent explaination and advice. I almost purchased a solenoid when I stumbled across this.
It took me about 40 minutes to complete the job and now the trans behaves perfectly. It was a perfect solution since this car will be used for little more than getting by daughter back and forth to school and around town, and best of all, it didn't cost a thing!
I'll unplug the relay when I get a chance so the OD indicator light will go out on the dash.
Thanks again,
Rob

THANK YOU THANK YOU THANK YOU!!!!!!!!

I have been fighting this problem since early Nov. and its not fixed yet!! I have gone thru 2 solenoids and 2 relays. And sent the darn thing to a shop, after I got bold and removed the valve body cover to clean it and then it wouldnt shift into drive at all. go ahead and laugh, i have already LOL. Now $550 later (rear main seal also) it shifts into drive but wont shift into 4th. The tranny guy got me back to my original problem. He seems to think that there is a sensor that tells the tranny when the engine is up to operating temp. thus allowing 4th to engage. We all know this is false on the 240. Needless to say, he wont be working on my tranny anymore. I will definately try this fix on my 240 as soon as I get home tomorrow. Being a Hydraulic tech. this never occured to me to try this. go figure LOL

CAT

PS. there are VERY small pins that have a tendency to fall out when you remove the valve body cover. One pin missing will not allow gear shifter to move past neutral. Ask me how I know.

Wow! That probably qualifies as the longest post ever on the Brickboard. The content is completely accurate.

May I add my comments.

There are times when we may wish to control the tranny a little better than with just a kick down feature. I live in North Carolina and have driven extensively in the mountains. While ascending at speeds from 45 to 60 mph I will often select 3rd to avoid the constant shifting back and forth between 3rd and 4th as the road incline changes, this gives me much better control and feel of my speed. Descending from the mountains often involves long downhill runs of 5 to 10 miles, again I am more comfortable controlling speed with tranny in 3rd rather than the brakes.

I suppose your solonoid fix is OK if you live on the prairies but for me I prefer to control the tranny in whatever gear I want when and if required, 1st 2nd, 3rd and 4th. That is the design of the AW. I have never seen a tranny design on any car that did not allow for this. For me I will continue to maintain the simple OD circuit as designed.
--
David Hunter

> have never seen a tranny design on any car that does not allow for
> this.

I have. Some Volvo 850s had a shift quadrant that went P-R-N-D-3-1.
My parents' old Lincoln had a 4-speed automatic with ranges for
OD (all gears), D (gears 1-3), and L (gears 1 & 2, but 1 is held
until redline when acceleration). Then again, being able to block
off top gear for towing and fast hill climbing is much more useful
than the ability to limit the car to 1st and 2nd gears, which is
what all of the cars which I described are missing.
.
-b.

I guess you must have really been trashed in the past. Hopefully it's not so bad that you can't have civil dialogs about issues.

Your technical critique of the design all seems pretty valid, however I can't imagine that this is the worst case of a foolish sub-system design in a car. Having my car for 17 years, and only ever having done a half-hour resolder on this subsystem doesn't put it high on my "what were they thinking" list; you've obviously fared worse with it.

Adding to hardknocks' thought, I think the ability to keep the transmission from shifting into 4th is useful for engine braking, when going down a hill/mountain with a gradual incline. It's better than riding the brakes. (Yeah, they could have implemented it better though).

hi there i can not think of a reason to have the relay setup. i have replaced the o.d. relay and also the wires from the passing buton down to the solenoid. that was fun. maybe one day i will have to do this procedure. o yea one good thing about the o.d. button if you see a cop and well you know, it slows you down with no brake lights.
;-}

Hmmm...

Carve a small passage way in the OD Solenoid to make the AT a 4-speed all the time. I remember hearing about this fix a while ago. I will make a note of it. Thanks for the info regarding how the OD electrical system works. That sure cleared up a lot of question I had. Thanks for your time!

Sincerely,
--
Julio Meza

1979 264GL B27F 122K

Features Added:

BW55 To M46, Central Locking System, 25mm IPD Front Sway Bar, 81+ Dash W/ Oil & Ambient Temp Gauges In C, Oil Pressure, Volts

Next Project:

+Cruise Control

If the solenoid is ok, but the relay is FUBAR, another option is to
get a rocker switch, stick it into one of the empty slots in the
dash panel, and use it to control the solenoid either directly, or
through a standard SPST-contact relay. A seat heater switch from the
junkyard should work fine for this application.
.
-b.

I, for one, appreciate the post. I wish there was some easy way to put this on a page on Brickboard for easy access once again. As it stands, it too will probably be lost to cycling of posts, just like the other overdrive posts.

I had the first problem you describe, a failed relay. The part's cost was within your price range, but at the top end (of course, straight from the Volvo place)--$50. All the work that is done is removing the gearbox and changing the relay out, so that's definitely the easier of the two repairs.

The solenoid, which gives clear indications when it's broken (from what I understand), is a whole lot more and obviously a pain to replace. I hope I never have to do one; rather, I hope I never have to take it to a shop to get it redone.

Good luck to those of you testing out permanent work-arounds!
--
'89 244 GL--25/22 ipd sways, Alpine head, Eclipse front speakers