I've enjoyed my 91 240 a lot. But I learned to drive in a '89 740T that had a manual tranny--a good old M46, the four speed plus the over-drive button in the middle. My present car--the Snake--is has the AW-70 automatic tranny. I can't complain about it--it works great. But, I really just enjoy driving manuals more.

So between mine and my brother's efforts, we've tracked down an M46 transmission and about everything needed to make the transition. If anyone out there is looking to make a similar change, I thought I would post my progress here along with my research.


This was my starting point:
Volvo AW71 to M46 Transmission Conversion

So, I'll start off with an inventory & discuss the challenges faced there.

The tranny from my donor car came from an '85. Some things did change between '85 to '91. Most importantly, my car has LH 2.4 fuel injection system. This presents two problems: First, LH 2.4 uses a CPS (Crank Position Sensor) to tell the computer where the engine is. The CPS reads divots in the flywheel. An '85 fly wheel has no such divots. Second, the bell housing has no place for the sensor.

The solutions worked out like this: I ended up getting a flywheel from a newer car. This added an additional layer of complication--the newer flywheel was a nine inch type with a lip on it, instead of the 8.5 inch version with now lip. As I decided to buy a new clutch, this was not a problem, I just had to be sure when I purchased the clutch I got the one for the nine inch flywheel.


As to the whole in the bell housing, my brother was in a position to cut a nice hole in the bell housing, so that is fixed. (I'll try to come back and post some pictures ((Done)).)


When I got the tranny, I also got the rear end. My plan is to switch out the gearing so I'll have a lower ratio in the back. (I think 3.7 to 3.3... but I have to double check that...) This may be rather complicated, and I'm still figuring out if it is feasible. According to OTP (Volvo's Original Technical Publications http://www.vcoa.org/component/conten...l-publications or the electronic form of their greenbooks) the castings for the rear end have the same part number.

I was concerned if the older gearing will fit in the newer pumpkin... but I do not think that will be a problem. I will likely go to a four wheeler shop to let them setup the differential. As interesting as that would be, not having an easy way to work on my differential, I don't want to have to keep getting in there to check on my work and tweak it. It's a dana 30, so it should be pretty familiar to them.

The other complication with switching out the rear end is that this being an ABS car, it has a tone ring that it uses to monitor the wheel movement. Oh, and importantly, it also is the origin for the signal that drives the speedometer. So I'd need to have the tone-ring retained--I can't just swap everything. I need parts from the old in the new. So I still have to investigate that a bit.

Related to this last part, I need to cap off the place on the back of the transmission where the old cable-driven speedos came from. This should be relatively easy.

Anyway I will post more as I progress and will try to add some pictures so this isn't super boring.

EDIT: I've added some pictures.

 

I find myself looking for the "like" button.

 

I've been looking a great deal at the 1985 and 1991 wiring diagrams. This is what it comes down to: I'd like to put the green 5 that lights up when you are in overdrive next to the trip-odometer reset button, in the center of the instrument cluster, the way Odin intended it. In the '91, that slot is taken up by the SRS light. Well... I don't know how much I care about that SRS light. The car is 22 years old, it is questionable if the SRS system even works. So, there are two questions I need to figure out: 1) Did how much did they change the wiring when they changed that slot from an 5th gear indicator light to SRS? 2)Is the SRS light an integral part of the SRS system? And if so, can it be bypassed?

Well, at question number 1, it looks like all volvo did was take out the 5th gear light, and put in place the SRS light.



And Below is the '91 diagram:


But... where I get into questions is the following diagram:



I'm not real sure what this "HIC" is. A few things seem to run through it. I've looked all over OTP for an explanation, but haven't found one. It doesn't show up in the abbreviations. (Or if it did, I didn't find it.) So while I know HOW to make the SRS light into a OD indicator light, I'm not real sure if it will screw up the SRS system. If anyone knows, I am appealing to the knowledge of the forum for this. Thanks.

 

Hazard Indicator Control, that's my guess. It shows it past the cluster connector, so I would pull the cluster and trace the path. According to the old car diagram it shows a direct path to the indicator light and then to ground. If the newer style dash has something in the path like an IC, I would think that you can simply bypass it. Scratch out the trace to it and go around with a jumper wire. It looks to connect the Alternator/battery light. I'm not sure why they would need to be linked and they appear to have what they need to operate without the HIC thingy.

The best answer is probably inspecting the cluster traces yourself and compare them to the old cluster.

 

In reference to the rear end, I wouldnt bother swapping it. I did an m47 swap into my 88 wagon and was initially worried about the gearing of the rear end. To my surprise, I LOVE the 3.7 gearing with the manual tranny. Has power in all gears. I'm not a hot-rodder, so I don't care about 3k rpm at 75 mph, as I rarely travel much faster than 70. Generally, I'm in 4th gear between 40-45 mph and cruisin with plenty of power. 1st and 2nd are really spunky too.

 

The 3.73 will give you more torque because the reduction is higher and the torque is multiplied. The torque out the output shaft is multiplied by 3.73. A lower ratio equates to less torque. The 3.41 that came out of the donor car (a 85 N/A wagon 240) will actually feel weaker than your car, but the idea is that you'll get better gas mileage. Engine RPM will be lower at the same road speed. So, everything you said makes perfect sense. It would be interesting to compare all the the cons and pros.

 

Yeah it would, but I've been tracking my gas mileage and I get about 25 on the highway, and 18-20 in town. Not bad for a 25 year old 240.

 

hmmm. our 1987 240 with a gajillion miles gets almost 30 on the highway, 25 in town.

 

I'm always happy to improve my mileage a bit. I get a pretty consistent 25. Most of what I do is back-roads or highways... in town is a pretty seldom experience for me anymore. But I still have to address that my MIL light still comes on, and I just haven't figured out what to do about that. If I tracked that down, It could improve things a bit. At some point I will. (it is the too lean/too rich code)

I try to keep my cars as driveable as possible while I am working on them. So, I am going to do this in 3 stages:

1. Add pedal & prepare electrical This will require removing the dash... so I kind of think this will be the most difficult part of the job. I will also be replacing the heater blower fan at the same time, since I will be halfway there. The electrical I will not be able to entirely do in this stage, as I need to keep the relay for the Automatic tranny in place until I actually change out the trannys.

2. remove and replace transmission I don't think this will be too bad. I've got most everything I need, and looked at all the differences. I have the new driveshaft, the tranny, it's wiring harness, a new clutch and a flywheel that should bolt to the engine and will work with LH 2.4. Of course, there will probably be some nuts and bolts that will be reluctant to turn, but I can deal with that. Also, in this stage, replace the relay.

3. change rear end ratio Again, we'll see what happens. I will drive for a while with the existing rear end ratio. If mileage is awfully good, I might not bother. I'll also do a cost analysis. Unless I feel really confident in my ability to set up a differential properly the first time i've ever done it, I'll probably get someone else to do it. And how much they would charge would make a difference.

EXTRA: Replace rear bushings Okay, I know I said there would only be three stages, but I have some bushings in the rear end that are pretty shot. I ordered the new bushings, and plan to replace them. This could happen at any point, though (between 1 & 2 or before or after any of these steps.

Anyway, I had a few minutes today, so I pulled out the instrument cluster and tried to make some harmony with it and the wiring diagrams.

I found the HIC:



And then I tracked the grounding and the supply to the SRS light:


The diagram is correct. (I guess that should not be a surprise.) But I still have no idea what the HIC does or to what extend bypassing it would mess with other functions. Sense nearly everything grounds through it, I am hesitant to mess with it too much. But I think the SRS light is the only light that gets it supply from it. So, I'm just going to leave it alone, and assume it is in some way important to the SRS system.

However, the farthest right light (location for the upshift indicator/overdrive off light) is setup very simply, and I am going to use it for my 5th gear indicator.

Also... I still need to track down a relay to run the overdrive in my M46. The automatic relay is very different and much simpler: when it receives a momentary interruption from the switch on the shifter ****, it toggles the OD on or off. The OD relay for the M46 needs two conditions: First, the fourth gear indicator switch needs to be closed. If that condition is satisfied, then the momentary on the shifter **** toggles the OD on or off. However, if the fourth gear indicator switch is open, it will not permit the OD to come on (probably just will not energize the relay).

So, I still have to track that down. But, things are otherwise coming along.

 

Find a number or something on the chip, I might be able to find a spec sheet.

 

is that just the 'voltage regulator' shown on most 240 'combined instrument' diagrams in group 38 ?

the diagram for the 1990 I'm looking at shows the SRS light comes from crash sensor pin 3 and the other side of the light is wired to . this same ground goes to some of the bulbs, and it also goes to this voltage regulator. (other bulbs are wired to power)

in the picture you posted above, it kinda looks like a diode under that plastic cover. I'd love to get a closer look at that, realizing you'd need a good macro lens, a tripod or something and a long exposure with good light and small aperture (large f/ratio) to get adequate sharpness.

the late 1993 240 diagrams show diodes from the controlled side of the (bulb failure, brake failure, and parking brake) lights, these diodes are all wired to the D+ side of the alternator light (I'm guessing these diodes force all those lights to come on when the alternator light is on, effectively a bulb tester).

the SRS light source also goes the OBD box under the hood

 

I am pretty sure it is not the Voltage Regulator.



In the picture, I have the heat sink removed, but it is over on the corner.

Here is one picture of the HIC. It will not be winning any photo contests, but it should give you a better idea.


The master wiring diagram on OTP is crap. OTP is very good in other areas, and the individual wiring diagrams are decent, but the master wiring diagrams are not scanned at a sufficient resolution to be readable...

 

Upon re-examination, I realized the plastic cover comes off.

again, this picture will not be wining any awards, but here it is.


I don't have any real macro lenses... so my old tamron 70-300 at close range is having to due. I'll have to pick up some extension tubes tomorrow. I keep meaning to, but forget.

And here is the wiring I know:

 

that coppery looking thing, hmm, could be a inductor ro something, kinda hard to say. EGs O2 or whatever isn't very helpful either, sigh.

I too studied the whole page schemas for a couple years and got not-very-far.

my gut feeling is, you could leave the SRS light unconnected, and it really wouldn't care, it would still work.

 

I think it's a diode and a transistor. My guess is it may take the 3.3 to 5v digital signal and boost it to 12v to drive the dash light. The diode probably prevents back flow into the SRS computer and the transistor takes the input voltage and outputs 12v. That's just a guess, but you could check voltage on the input from the SRS computer and if it's computer voltage (5v and lower) it would make sense.

 

the signal that goes to the dash SRS light also goes to the diag box according to my prints. AFAIK, the diag box stuff is all 12V. the LED in the diag box is wired from the jumper to +12V via a current limit resistor, and the button is wired from the jumper to ground. when the selected control device (ECU, ICU, ABS, SRS) wants to blink the light, it pulses it to ground.

 

Well, that ends that idea. It's clearly a whatchamacallit.

 

I got my tranny up on an engine stand the other day, so now, I'm cleaning it out.



It has been interesting to take it apart and see how it all works.



Pulling off the top cover revealed how the shifting system worked. I always had a vague idea, but now it is quite clear.

Looking down into the gears is also neat.



the gear with the stright teeth is the reverse gear, and doubles as collar for 2nd gear. Also, I understand now why reverse is so loud when you shift into it--the idler gear just slams into place. the "Clunk" you hear is the gear sliding along its axis and slamming into the tranny casing when it reaches its desirable position.

I drained the oil out of it.



The magnet on the oil drain plug collected a good deal of debris.

Then I went to work on the overdrive transmission. I pulled off the bottom cover.



to open those black covers up, I just used a pair of needle nose plyers, and twisited. That got two out. The third one I didn't really want to pull anyway.

So I pulled out the big plug, and got the filter out.



The greenbooks call for cleaning it with "white spirits" and shop air. I used gasoline instead of white spirits and then the air, and got decent results.



There was quite a bit of metal in this filter, too. AFAIK, the OD transmission and the regular transmission share fluid, so I'm guessing that the majority of it just collected in the filter. That makes sense, anyway.

I also pulled out the next black cover, but it was just a check valve, and was quite clean. So I didn't bother trying really hard for the last cover. Also, you can see from an earlier picture that if I had gotten open the last black cover, it would have torn up the seal... and i'm not looking to replace that unless needed.



As a side note, you can see the strainer and bottom cover for the OD in the above picture. It is cleaned in the picture. Again there is a magnet on the bottom of the cover, and it had a nice sludge all over it. I am sorry I forgot to photograph that.


I'm deciding if I want to re-paint it at all, or what I can do with some of the rust. None of it looks bad... but as I have it out and it is easy to work on... I may just do that.

I was going to avoid replacing seals. All the covers I have gotten off are intact. Any thoughts?

Finally.... I got to the speedometer gear. Strange thing... the whole unit just comes right out.



It fits in there with an o-ring. Then there is a retainer that is supposed to screw into there to keep it from falling out. Curiously, the whole above the speedo gear didn't seem to be threaded. Anyway... figuring out how to seal that up does't look like it will be too hard.

So... that is where I am at.

Also... sorry about poor image quality... shooting with my point and shoot that is reserved for greasy hands.

 

old bicycle restoration trick for getting rust off steel parts. DO NOT USE ON SOFT METALS, iron/steel only!!!

make a strong solution of oxalic acid ('wood bleach', available at any home improvement store), in a plastic container, submerge the parts, and wait a few days. remove, thoroughly rinse off, dry and lubricate. the steel will be shiny, the corrosion entirely gone. of course, anything that was heavily corroded is now pitted.

stuff is fairly safe too, although I do recommend wearing rubber gloves, and a face mask to prevent it from splashing in your eyes.

 

Thanks for the great pictures! That is really neat! Keep them coming, motor/tranny disassembly pics are always resourceful.