I really love this little truck. Had it for two plus years now since about 180k miles. Changed out both cyclinder heads for leaky valves and it runs and generally drives very cleanly. Bit underpowered but that’s ok. Now the issue - I have seen dozens of threads but I don’t THINK they match my issue but the problem description hasn’t been specific enough so here goes

it’s hard to get into gear sometimes. Most often with 1st gear and sometimes reverse. To be really specific it’s the same engine running / stopped and moving / stationery.

it feels like the flats of the gear faces are not meshing and sliding into lock. There is no grinding or other sound like the gear synchro speeds are wrong. The clutch engagement is solid in gear and disengage is clean.

a lot of threads say Slave or master cylinder issues that fail to spin the disks to align - but wouldn’t that make grating sounds ? Willing to switch out the slave or master if the symptoms match that as the likely cause but I would rather not start work on it if I have a low expectation of success. It’s been this way since I got it and my guess was worn synchro with likely gearbox replacement if it got worse. But that’s a solid major job and investing 1500-2000 in a 17 year old truck worth maybe 5-6k seems whack.

we are at near 190 k miles so it isn t unreasonable that wear and tear have taken a toll

 

Transmission gears are connected directly to the rear wheels, so the gears spin at rear wheel RPMs
When stopped the gears are at....................0 RPM

The clutch disc, on the other end of transmission, spins at engine RPMs, 600-800 at idle

800 does not go into 0 very well, lol

The clutch disc is sandwiched in between flywheel and pressure plate, both are attached to engine directly so spin at engine RPMs always
When you press down the clutch pedal that should PULL BACK the pressure plate, releasing the clutch disc, so it can slow down to 0 RPMs so you can put transmission in ANY Gear when stopped
If there is ANY rubbing against flywheel or pressure plate then clutch disc can't slow down to 0 RPMs easily
Air in the clutch system is the usual problem, the pressure plate is not FULLY releasing the clutch disc, so it can't slow down on its own, you have to push the shifter into any gear which can slow down the partially released clutch disc
Some times its easier to put it in 3rd or 4th when stopped and then into 1st or reverse, once shifter is in ANY gear when stopped clutch disc is at 0 RPMs

But it reads like you have air in the system, it can hide at top of Master, very hard to clear that air because of the angle of the Master

 

I looked HARD at all those posts on leaking / air / water in the brake fluid - but no one talked about gear crunch feel / sound which I would have expected if moving gear has to engage with stationery gear (which is what I THINK the effect is of air or potentially water or a leak in the clutch system). No, I dont get any grating sounds - I know those and feel them every time my teenage learner does not quite get his clutch timing correct - and in my youth I have both used double declutch and no clutch gear changes, and even driven the old Fiat 500's with no synchro on reverse.... so lots of feel on driving and this is different (but these are newer systems than in my youth when I started with an NSU Super Prinz aircooled 600CC engine that I rebuilt at least a dozen times).

I am not saying its NOT this because I do sense a more solid '******' when the gear engages which would fit that the plate hasnt stopped spinning but maybe does when the gears engage - but that ****** ALSO happens in higher gears when the wheels are not stationery....but maybe again, same thing, its spinning the plate up if the shift is slow... I will have a look over the weekend and visit a clutch mechanic on Monday (hes busy today) for a chat about it but also check what I can myself this weekend.

Thanks for the comment - the ability to visualize helps - maybe I am feeling the engagement clunk rather than a gear skid / grinding. I kind of think because its similar in all gears its maybe not the gearbox itself (which would be a relief !) but in the clutch engagement process / mechanism

 

No grinding because the synchro's RPM match before the metal gear teeth can rub/grind, but synchros are what makes it hard to get into gear when stopped if clutch disc can't slow down easily to 0 RPMs, as you push the stick forward into 1st, for example, the 1st gear synchro is pushed against the gear, which is at 0 RPM which should slow down the clutch disc to 0 RPMs instantly.........IF its not rubbing
That's what sychro's do, they RPM match the selected gear with Clutch disc RPM for smoother shifting
Your M5OD-R1 has synchros on all gears including Reverse

But simple test is to see if it shifts in to 3rd or 4th or 5th when stopped without issues, if so then not clutch RPM issue


1st and 2nd do share the same shift rod and shift fork, worn shift fork or bushing could be causing a stiffness when sliding the rod and fork to 1st and 2nd

 

Yeah. Same in higher gears stationery so probably not the forks. Fluid full so probably not a leak.

 

Clutch disc is rubbing