Volvo 240 m46 problem with 1 gear grinding when engaging

[Echo1975]

So this problem happened again where if I am moving and try to put 1 gear in, it won't go in easily and I can hear gear grinding and when I push on it harder it goes in.

This happened around 6 months ago and it stopped happening in 2 weeks and only came back now.

More in depth when slowing down lets say in 2 gear and I press the clutch in and try to engage 1 gear, I feel no resistance in the shifter and just hear gear grinding until the gear goes in.

I'm baffled considering it went away on its own the last time and it's back without me doing anything.

What could this be?

[RedArrow]

1.
I would start by checking and replacing the transmission mount AND the engine mount as well (especially focus on the left side engine mount).

There`s a chance that these wear-item parts of the unit reached a point where the overall alignment is not 'comfortable' anymore for the tranny, the engine, or both. Bad mounts can make shifting into 2nd/1st very hard or "impossible" at times.
I`ve been there multiple times when my mounts were badly worn, sometimes invisible though, and I could slowly, gradually feel the tranny not wanting to be shifted into 2nd, more and more as months passed by, until I finally installed a new tranny mount/Left engine mount/or both.

BTW. I never, repeat, NEVER shift into 1st gear when the car is still rolling. I put the shifter into 1st gear only after a complete stop. This may sound as crazy as it sounds but this is how I do it, maybe it helps, (maybe it doesnt help) to reduce unnecessary wear in my m46 tranny.
Plus, the 1st gear is simply way too short anyways.. and I hate to hear when/if the engine doesnt like the 1st gear coming from a rolling stop.

Indeed, my shifting troubles , started either in 1st or in 2nd gear, usually when I slowed down and tried selecting 2nd or 1st gear at a stop sign or traffic light... appeared most of the time if the car was still rolling.
Multiple times these issues disappeared right after I installed a new tranny mount but often my car wanted the engine mount to get replaced as well.

2.
Also, check the fluid level in the tranny but I doubt that it is that what`s causing your shifting troubles this time.
Although, my tranny once had only HALF of the fluid that was supposed to be in there but it did not cause symptoms you were describing. Adding fluid definitely helped with the smoothness of the gears, especially when I replaced all of the fluid (and even topped it up above the high mark, just by a little).

3.
Other times, my shifting (into 1st or 2nd) troubles were also caused by extremely worn shifter bushings which really made sense to me when I went under the car to inspect them. They looked shot. Immediately after adding those two little plastic craps, shifting gears felt 'night-and-day' and shifter slop disappeared. It used to wobble a lot, even at idle.
make sure to not strip the hex-head down there. Easy, fun project with good results when/if they happen to be worn, definitely worth a check, and won`t hurt the check...

These 3 things come to my mind as things to check, because it literally costs nothing to check on them. Parts are cheap and fixing these 3 seems to be a very easy thing to do even if you only have just a few hours to work on your car.

What is the history of your car, the tranny, and, do you 'gently abuse it" sometimes?
Let`s hope that your shifting troubles are not caused by an internal failure and wear. These m46 trannies are very durable if cared for. Usually they do last at least as long as the engines do. There are exceptions
Use the proper fluid if you decide to change it.

Report back to us after you found the source of the problem!

4.
Small adjustment is also possible near/under the shifter, done from inside the car but it is mainly for making a comfy 'track' for the shifter (when I adjusted here it took the 1st gear better, especially the Reverse--- the bracket was limiting the shifter from reaching out enough to the left side towards the Reverse gear)
I would not do this unless very very obviously necessary. Maybe see all else first and try to figure it out without thinking this adjustment will make any difference.

5.
Clutch cable adjustment
See the clutch cable unit under the car, it is easy to figure out what to do. As the clutch wears, you may need to readjust the cable here.

Questions to ask from yourself;
Have your shifting problem developed somewhat slowly and gradually (throughout at least a couple of weeks of driving),
OR is it something very `new` to you?
How does the clutch pedal feel compared to how it used to feel? etc
Any changes in that, anything to mention about how and 'where' it engages?
Does it ever 'throw out' 1st or 2nd gear sometimes? Once engaged, does it hold it really well even at higher revs in a moving car? etc.
Without overthinking much, I would strictly focus on 1,2,3,5.

My clutch pedal used to feel kind of soft and only engaged at the very bottom of the floor (at the very end of the pedal`s path) so I never really liked it but it is what it is, cable adjustment somewhat helped, it improved a slight bit.
If you cant figure out what is grinding, do not use the 1st gear at all. Grinding has no benefits

[RedArrow]

Originally Posted by Echo1975

try to put 1 gear in, it won't go in easily and I can hear gear grinding

and when I push on it harder it goes in.

On the clutch pedal or the shifter?

[Echo1975]

Originally Posted by RedArrow

On the clutch pedal or the shifter?

The shifter.

The issue suddenly appeared. The car works normally except for the grind. I've had no issues with the transmission other than first gear grinding and overdrive wiring issues.

Both engine mounts and the transmission mount were replaced months ago.

I've replaced the fluid 3 times.

Bushings are quite worn seen by wobbly shifter but alla gears go in nicely and I never miss gears.

I drive the car harder than most people would. It's a NA diesel so not much power to break anything. It has good enough low end torque to get going in 2 with just the clutch similarly how a gasser would get going with using the throttle so don't need first gear that much haha.

I think the only thing that could cause first gear grinding would be a syncro fault like dirt or mechanical issue but considering the issue went away on it's own the last time has me baffled.

It surely can't be mechanical damage because that shouldn't go away without doing anything.

[Goteborg Vapenfabrik]

Have you ever had the M46 gearbox out to be able to examine the clutch components such as the pilot bearing, pressure plate, clutch disc or release bearing? If not is there any history of clutch component replacement?

[RedArrow]

Originally Posted by Echo1975

The shifter.
I've had no issues with the transmission other than first gear grinding and overdrive wiring issues.

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)?

[Echo1975]

Originally Posted by Goteborg Vapenfabrik

Have you ever had the M46 gearbox out to be able to examine the clutch components such as the pilot bearing, pressure plate, clutch disc or release bearing? If not is there any history of clutch component replacement?

I haven't examined the clutch and it probably has been over 25 years since anything was done to it considering the car had sat for 2 decades when I bought it.

[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