Volvo 240 m46 problem with 1 gear grinding when engaging

[Echo1975]

Originally Posted by RedArrow

It is very annoying that all of our wires got biodegradable by now. Bad quality.
The wires underneath the shifter and even the wires within.

I had to replace all, in fact I am still in the search for a "4th gear contact switch" (OD interruptor plug)... until then, the car is currently an 8-speed manual because I had to rewire the tranny so I can use the 5th gear without using the 4th gear contact switch (by switch I mean the switch itself on the tranny itself, below the chassis...not the button-switch on shifter).

The car works great this way, it is sometimes even fun. Except that it is dangerous and risky bc if the driver puts the OD on while in reverse gear, the tranny will not be happy, at all.
1, 1+od, 2, 2+od, 3, 3+od, 4th, 4th+od="5th"=OD.... 8 gears I barely use them though. I shift the regular way.
The 4th gear switch is reachable without lowering the engine/tranny. It is a tight space but it is very doable without any specialty tools.

Once I find a new 4th gear switch, I will reverse this 8-sp wiring project to get back to how it originally was, a 4speed with pushbutton OD.


Any progress on figuring out what causes your shifting problem and grinding (1st and 2nd gear)?

I love the idea of having 8 gears and luckily I have managed to drive without many issues. The only problems with my 240 that haven't been caused by me are really the transmission and electrical system issues such as having to mess with the fuses sometimes and bad grounds etc.

I have a few small issues with my OD like for example if I pull the shifter to the left it turns off so you have to keep your hand away from the shifter when in OD and I also got that issue where when it's really cold it won't engage for a while.
It recently hit -2f and I couldn't engage OD for 4 miles but I don't mind unless it stops working completely.

With the cold weather came snow and it's been a blast because I've got the dana powerlock lsd and that works brilliantly. Makes me feel like a pro drifter

Been getting pretty good mileage too. No matter how I drive, I seem to always get 31 mpg.


The grinding hasn't gone away but I checked the transmission fluid and found that I was about half a quart low on oil. The transmission is leaking very slowly from somewhere and I don't bother fixing that.
I doubt the low fluid caused my issue because when it last occurred half a year ago or so I wasn't low on fluid.

[RedArrow]

I had the very same issues with my OD, even intermittently turning off at bumps on the road, including at high speeds of 75-80mph (annoying!!!), delayed use in lower temps when I had to "wait" for miles and miles until I was able to turn it on...just to learn that it would keep popping out soon after... lots of holding the shifter to the right side while driving... stupid and dangerous. Later this would worsen too, holding shifter to the right wasnt enough...it happened more and more often after hitting less and less bumps or regular road vibration or even a slight tilt in the roadway was enough to trigger the unwanted cut-out.
I thought the OD internals were failing but now I know all is fine.

I think your 4th gear switch in transmission is worn out.
If you decide to go under the car, disconnect the 4th gear contact switch on the top of the tranny by removing the single wire that runs to it. Not the one with two wires, that is the Reverse light switch. Find the single- wired one on the right front side of the top of the tranny. Google some pictures before it.
Just unplug it carefully... Try to not break the plastic. Ground this wire to the negative on the tranny or to the negative tab on the solenoid. Dont mix the polarity it must be a negative.

If you do this mod, you will be able to turn it on EVERY time in ANY GEAR. yes even in reverse so be careful DONT ruin the tranny. IDK if using od in gears other than 4th gear can hurt it or not.
Avoid forgetting OD on, use it ONLY when intended: in 4th gear!! Avoid accidentally using it in Reverse gear.

If your OD will work fine with this mod, you will know what to order: 4th gear contact switch, also called an overdrive interruptor switch; pictured above earlier.

My OD never popped out of 5th gear ever since, not even once. And it's been years, operating fine. I should finally buy the damn switch and turn it into the tranny. An easy project, no lowering of tranny is needed but it is a hard to reach spot.

[RedArrow]

My m46 has a noticeable little seeping at the rear output seal. There is no leak but it looks a little shiny there so I know.
This explains why I missed fluid when not checking for so many years. Use the proper fluid only! I tilted the car and slightly* overfilled to compensate temporarily.
(I will tackle the output seal project hopefully in Summer.)

When I replaced fluid I also removed the square OD cover for a perfect draining then cleaned the filter in there, also removed the little pistons and parts for inspection and cleaning. Found grey metal paste in filter, it was worth checking!

The pan gasket is still available to order, I already bought one. Very careful when tightening drain plugs and the four small bolts holding overdrive lid. It is just an aluminum cover, not the crank nut

[RedArrow]

Originally Posted by Echo1975

checked the transmission fluid and found that I was about half a quart low on oil. The transmission is leaking very slowly from somewhere and I don't bother fixing that.
I doubt the low fluid caused my issue because when it last occurred half a year ago or so I wasn't low on fluid.

A half liter/quart of tranny fluid in just half a year is not "leaking very slowly"