There have been numerous posts over the past few years on the notorius 240 Overdrive Relay Circuit, along with various troubleshooting steps. Several months ago, "Roger Scott" posted a GREAT message on an innovative "upgrade" to the entire overdrive relay circuit.




IN A NUTSHELL, the technique was to modify the Overdrive Solenoid, allowing transmission to "pressurize" the fourth gear without needing the overdrive circuit at all, thus creating a full-time 4-gear automatic transmission.



Click here to review the original link:
[Volvo 240 Automatic Transmission Overdrive Circuit]



MY QUESTIONS: Has anyone ever applied this technique (besides Mr. Scott)? How long does it take to remove/install an OD Soleniod? How long does the modified OD Solenoid last? Do leaks occur around the modified OD Solenoid with the "C-ring" gasket in place? Has Chris Herbst used this technique to date?



My 1991 240 Overdrive Circuit failed yesterday morning. Once the temp gets above 32-degrees, I will start troubleshooting. But when I ran across Roger Scott's fabulous info, I started to totally rethink my approach. Should I repair the (poorly designed) system, or use his approach to make the whole think more reliable for months/years to come? Chris Herbst, did you get this added to the FAQ? I could not find it there.

[[ southern fried volvo '91 240 ]]

My 245 has been running for about 7 months with this 'fix' and works like it has always been a 4 speed automatic! I towed another 244 back from western Kentucy with it over the smokey mountains with no problems. Just remove the solenoid, drill out between the passages and re-install without the inner o-ring.

Will Dallas
www.willdallas.org

I used the OD solenoid "fix" when I was stranded in New Orleans without any money or means to buy a new solenoid on a weekend. It was on my Dad's '86 240. I used a dremmel tool to carve a channel after removing the solenoid. We drove all the way up to Nashville with the fix. To date, no leaks. Works fine.

For what it's worth, the OD on my '90 240 failed last week. I was forced to drive several hundred miles in third gear (how embarassing.....)....

Resoldering the relay DID NOTHING (how embarassing for me...).

Fixing the broken wire, however, made a world of difference.

The wire from the tranny tunnel and going to the solenoid had corroded completely through at the connector.

Be absolutely sure your solenoid has failed before you make an irreversable modification to it.

Another risk: Snapping the solenoid bolts in the tranny case. If this happens, you're in a world of hurt.


--
Don Foster (near Cape Cod, MA)

I've got to agree with Bob here, there are many cases where I want more rpm out of both the '88 and '92 without mashing the pedal to the floor to kick it down. fix it right it's not that hard.
--
Dave Shannon
Spring Valley, California
'65 1800S ????K
'67 1800s 79K
'73 1800ES 117K
'88-240 190K+
'92 745Ti 160K
my pages

A drawback to the non-defeatable OD, as I see it, is that you can't hold the trans in 3rd on those occasions when you are ascending (or descending) a long hill and want that particular gear. Other than that it seems like a good fix.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and numerous old motorcycles)

"A drawback to the non-defeatable OD, as I see it, is that you can't hold the trans in 3rd on those occasions when you . . . want that particular gear.

After reading Scott's article and the subsequent comments, my impression was that you could still drop from 4th to 3rd gear via the Kickdown Cable. Punch the accelerator, and the transmission will downshift. (That is how I normally "shift" when passing. I have used the "Overdrive" button only twice in the past five years on my 240.) Did I misunderstand the technical info?

Thanks for the additional input. I am looking for the PROs and CONs of this "Overdrive Upgrade". Has anyone else done it? How long does the modified OD Solenoid last? Until the wheels fall off?

[[ southern fried volvo ]]

Yes, I believe the kickdown function is unaffected, but I was referring to the manual lockout, which I like to have and do use fairly often.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and numerous old motorcycles)

but I was referring to the manual lockout, which I like to have and do use fairly often.

I second that opinion. There are many times when I'm traveling on the highway and I drop to 3rd gear for a sustained uphill climb (without mashing the gas). It's also nice to provide a bit of engine braking on long downhill runs when the vehicle is heavily loaded.

However, I do realize that there are a lot of drivers out there who never manually downshift and wouldn't have a clue what the button on the shifter lever is. The functionality of our overdrive lockout feature is not equally appreciated, and when attempting repairs of such a unit, consideration should be assessed as to the needs and habits of the driver(s) and the loads carried.

God bless,
Fitz Fitzgerald.
--
'87 Blue 240 Wagon, 252k miles.

Yes, I believe the kickdown function is unaffected, but I was referring to the manual lockout, which I like to have and do use fairly often.

I agree with you. Plenty of moderate hills around here where I prefer to climb in 3rd, rather than be drifting in and out of OD.

And what is so "notorious" about the relay-controlled solenoid circuit anyway, except maybe the "toggling" relay? Is it the "negative logic" on the panel indicator light (upshift, or "OD Off)?

Seems like the AW 70/71 operation is basically the same as with the M46 OD, where we energize the solenoid for OD and deenergize for direct drive.

But no one seems to get their knickers in a twist with the M46 solenoid.

What am I missing?

--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

But no one seems to get their knickers in a twist with the M46 solenoid.

I'm not sure dispassionate scientific discussion of this is going to happen.

The post recommending the bypass of the OD solenoid is written with persuasion in mind, to give relief to those do-it-yourself mechanics who drive mainly on the plain and don't find themselves comfortable with electrical circuits.

I'm sure the idea to dremel out the solenoid could have been conveyed without attempting to divide us all into two camps - those who might fear "short circuiting" a hydraulic passage in their automatic transmission against those who fear doing the same on the circuit board in a relay behind their dash.

I don't find anything "silly" about the OD off button on the automatic. But I'm sure we all think the wire under the car could have been better protected.
--
Art Benstein near Baltimore

Hello Art,

Since I have several with and only one without a selectable OD (which has been driven in both flat land and high mountain terrain under towing load with good results), I have looked at other alternatives to the ill conceived design of the Volvo OD control circuit. One of them is to convert to an Idec latch relay which would probably never fail. I have the part numbers and schematic if you are interested.

Will Dallas
www.willdallas.org

Hi Will,

Your story about towing through the mountains intrigues me. I have not tried that yet with a Volvo. But I thoroughly enjoy driving through the mountains when the weather is nice; we make the effort to choose a different path to Ohio on every trip, looking for the most scenic West Virginia, Maryland and Pennsylvania mountain roads.

On each of those trips we try to use a different Volvo; though now we will need to go into re-runs. I think our favorite in the mountains is the 242ti/M46- at least it is my favorite; my wife thinks I take the curves too fast.

But on all of those mountain pulls, up 8 to 10% interstate highway grades (you Westerners don't laugh now!) when using the N/A cars with AW-70s, the kickdown would jolt us into being aware we were falling behind the bimmers while passing the semis, whether on cruise or not. Then, after a few episodes with the momentary racing brought on by the kickdown, the OD off button would take us right to the top without the jerking.

Not towing anything, I probably didn't need it coming down the hill, but somehow I felt more comfortable heating up the transmission fluid in third, than warming the brake rotors.

Now, an admitted nerd, born knowing which end of a soldering iron to grab, I did not find the OD control circuit to be ill conceived. But there are two, and only two that I know of, bugaboos with the implementation of it.

The first, I believe, is the white wire under the car. Thankfully, it was well supported from the solenoid itself to the connector, otherwise we would be changing a lot of solenoids just because the wire broke or dissolved off of the solenoid case. But the rest of the wire, to and through the shifter box tends to look like some of those poorly formulated 80's harnesses after 20 years under the car. It usually shorts to the tranny case, but as Don's reply indicates, can fall apart altogether.

The second bugaboo is one not confined to just the OD. It affects all of these small electronic control circuits we refer to as "relays". It is a manufacturing defect that occurs when the circuit board assemblies are wave soldered in mass production. The problem has been known since the very first production soldering wave machines of the sixties: a large component with a large thermal mass, such as an open frame relay, requires more time in the wave than its neighboring resistors, capacitors, diodes and transistors. But the assembly only makes one pass, so the time (heat tranferred) must be a compromise with the maximum allowed to the sensitive small components with little comparative thermal mass. The result is cold solder joints that later fracture, as they are subjected to mechanical and thermal stress.

Best p-ography I have of a candidate for microsurgery.

Hi Art,

Thanks for the info on the OD circuitry. While I appreciate the ruggedness of the Volvo automobile more everytime that I drive one, I just can't believe that the Volvo engineers designed an OD to fail in the closed mode. While an across town drive with the OD oil circuit closed would not tax your engine, a couple of hundred mile freeway trip at 4,500 rpm would get on my nerves. I would like to modify a small Normally Open solenoid to replace the stock unit and let it bypass the OD on demand. It would probably take a remote mount of sorts, but I believe it can be done.

My background is industrial controls so I always look for ways to improve old relay devices. IDEC # RH2LB-UDC12V is a latching relay with heavy contacts rated for 10 Amps. The matching socket is SH3B-05. I have the wiring schematic that would allow the same momentary switch to latch it on and unlatch it. While I've not tested it out yet, I am going to install one in either my 940 or 760, whichever goes first. I'm also thinking of programming a small PLC to handle all of the relay functions on one of these cars and relocating everything in minature (OMRON) to the engine compartment.

When I was towing the first car with the 245 that I altered the OD solenoid on, the car (with the pedal on the firewall) would downshift from OD into third gear at 50mph. At 60 mph it would upshift back into OD. This was on the heavy pulls between Knoxville, Tennessee and Asheville, North Carolina. Going down hill I used the brakes to keep under 65 mph. These transmissions are a lot tougher than one would expect for the engine size. I've not rebuilt one yet, but am looking forward to it!

If you get to Charlotte on one of your trips, come on by.

Kindest Regards,
Will Dallas
www.willdallas.us

Hi Will,

I think I understand now, the lack of hunting in your fully automatic mode, when the pedal is firmly held to the firewall. That must be due to the payload or steeper Smokies. The easier hills I recall only required part throttle yet we'd be losing ground running in 4th.

But, I failed to include my experience of one of those trips across the hills and into the Midwest. The one in our '79 with AW55 three speed auto. Hundreds of miles would be cruised at 4000+ rpm. Aside from the noise and not-so-great fuel efficiency, we could not detect any ill effect on the motor or its cooling. But, the noise is unnerving and a frequent reminder of the luxury of overdrive ratios.

Regarding your looking forward to rebuilding an automatic, I think we differ there, though I'd be prepared to if there were not so many good ones in the yards. There's this vague memory I have as a kid, Torqueflite in the bathtub. Then back in there again. Then conversion to manual.

But you do mention a 760. ZahnradFabrik? I have it in my mind to stay clear thereof.

I like your thoughts about customizing improvements, something I've not done much of in the Volvos. When I did, I used to worry when I left town.

Thanks for the offer!
--
Art Benstein near Baltimore

Hi Art,

Yep, an 88 760 GLE Turbo Wagon. It was one of two good looking wagons that I got in the 5 Turbos for $700 package. I stripped and scrapped 3 of them and started restoring the 760 first. It went on the road last Friday, and I must admit that it is a real nice ride. You probably are wise to keep well clear of these because of the electrical system (as compared to the 740s). It is totally different than the same year 740 wagon, and even the relays are different. I did figure out how to wire in a toggle switch under the hood to test the fuel pumps (or bring it home in case of relay failure).

My wife is going to take it away from me anyway, and since I listed the 245 today, I am back to our 940 and an 86 244 that is going to get a nasty turbo package.

The invitation stands,

Will Dallas
www.willdallas.us

I'm not sure dispassionate scientific discussion of this is going to happen.

I expect you're right as usual, Art. And it all started so warm & fuzzy too (I checked the link).

Guess if the solenoid is proven to be NG, then one can save $100 or so this way, and give up the manual downshift function.

But I'd never consider it a reasonable alternative to diagnosing and fixing the simple switch and relay circuit that controls the solenoid.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Thanks, guys, for the input. After comparing Roger D. Scott's original post to all your comments, I am going to repair the fault instead of modifying the OD Solenoid.

So here is another question, probably the one I should have asked at first:

Do you guys recommend any "improved" insulation for the OD wiring in the transmission tunnel? Heat-shrink? Plastic tubing? How can I keep this from occurring next year? 9If I am going to repair it, I might as well do it right.)

[[ southern fried volvo ]]

Use a THHN copper wire at least 16 ga. Run it through a 3/8" high temperature hose to shield if from all of the heat and grease. Heat shrink the ends of the hose for a seal.

Will Dallas
www.willdallas.us

So how about some pics. I would like to see how it is done so I can consider doing this to my 89 Brick. How about a link.

Bigmeat

Hey I removed overdrive swtch from gearshift knob and installed a jumper wire between the two wire, Still no overdrive or overdrive light on the dash. What now?

So does anybody have any good pics they can post or email me.

kd4uld@earthlink.net