Why so hard to shift gears

[Lumbar Jack]

Hi All,

I recently bought a 1952 M37 from a fire department. It runs and drives, but I’m struggling with how rough and sloppy the gearshift is. Such a workout to change gears, I expected to find no oil in the gearbox, yet it’s full. Not the first time I’ve driven an old truck, I have a ’70 Pinzgauer and a ‘80 Series III Rover. I thought the Rover was rough to shift, but it’s easy compared to the M37.

I’m working on my double clutching.. is that necessary only from 1st to 2nd, or in higher gears too? Trying to figure out: do I just need more practice, or does this indicate something wrong with clutch or transmission? Maybe both? At this point, I'm glad to park the truck after a 10 minute drive.
Appreciate any suggestions.
Thanks!

 

[John Mc]

I don't find my M37 difficult to shift - either before or after the transmission was rebuilt.

1st and 2nd gear are not synchronized, so you will need to double clutch to shift into them .- Or you can "rev match" (shift into neutral, then get the engine going at the RPMs it would be if you were already in that gear, then shift. Done right, you can shift without using the clutch at all. I find it easy to do shifting up from 1st to 2nd, but it take more practice to do when downshifting.) 3rd and 4th gear are synchronized, so there is no need for double clutching.

 

[G744]

There is a pin that locates the shifter lever and keeps it from 'wandering'.

It is located at the top of the shift tower, perhaps yours is broken or missing.

DDG

 

[Mullaney]

Hi All,

I recently bought a 1952 M37 from a fire department. It runs and drives, but I’m struggling with how rough and sloppy the gearshift is. Such a workout to change gears, I expected to find no oil in the gearbox, yet it’s full. Not the first time I’ve driven an old truck, I have a ’70 Pinzgauer and a ‘80 Series III Rover. I thought the Rover was rough to shift, but it’s easy compared to the M37.

I’m working on my double clutching.. is that necessary only from 1st to 2nd, or in higher gears too? Trying to figure out: do I just need more practice, or does this indicate something wrong with clutch or transmission? Maybe both? At this point, I'm glad to park the truck after a 10 minute drive.
Appreciate any suggestions.
Thanks!

.
Mine has some "slop" in the shift pattern, but after the first ten or fifteen minutes that I drove it - it shifts like a dream. It isn't a Hurst Shifter or a VertiGate Shifter either. The pin that @G744 mentioned is a good place to look.

 

[Lumbar Jack]

There is a pin that locates the shifter lever and keeps it from 'wandering'.

It is located at the top of the shift tower, perhaps yours is broken or missing.

DDG

Could you post a picture of that pin, so I'll know where to find it, and what it should look like? Thank You !

 

[CMPPhil]

Hi

A question what is the idle RPM? I've noticed with straight cut (non synchro) transmissions that if they are idling to fast they are hard to shift up through the gears. Also have noted that when double clutching down if the accelerator is weak and the engine is slow to burp up it is harder to match speeds to shift down.

This problem is compounded with ethanol gas as it ages, it doesn't let the engine idle down to 400 or 500RPM and at the same time when try to burp the engine up to down.

Cheers Phil

 

[Lumbar Jack]

Hi A question what is the idle RPM? I've noticed with straight cut (non synchro) transmissions that if they are idling to fast they are hard to shift up through the gears. Also have noted that when double clutching down if the accelerator is weak and the engine is slow to burp up it is harder to match speeds to shift down. This problem is compounded with ethanol gas as it ages, it doesn't let the engine idle down to 400 or 500RPM and at the same time when try to burp the engine up to down. Cheers Phil

Hi All,
Thanks for the suggestions. Shifting is gradually getting a bit easier, with practice. If anyone could post pictures of the pin that locates the shifter lever, that'd help. RPM level is about right, I think. Here's a new but related question: In 4th gear, something feels wrong, it feels like the clutch is slipping.. the truck just doesn't respond like it should. No sign of that in gear 1, 2, 3. But why would the clutch slip only in 4th? I'd expect slippage in low gears, which have higher torque. Maybe it's not clutch slippage I'm feeling? Something's wrong in 4th. Suggestions?
THANKS!

 

[CMPPhil]

Hi

Do you have access to a clip on tachometer, like a timing light? If so take the truck up a gentle hill in 4th gear and floor the peddle at about 30 MPH
If the tach picks up faster the road speed the clutch is slipping.

Now why would this be more noticeable in 4th than lower gears, simple the gear reduction of the lower gears means torque is multiplied in the transmission after the clutch. In 4th the torque produced by the engine is the same as delivered to the drive shaft. The only thing that can slip is the clutch.

Now before you take out the clutch, check the adjustment of the pedal just a little out can make slip also check the clutch housing for signs of oil. I don't know on M37 is there an fording plug and inspection plates? I've had the problem you are describing with some of my WWII trucks and was able to solve the oil slip by removing the bottom cover depressing the clutch (engine not running) an spraying the clutch disk down with break cleaner. Delayed replacing clutch disk for a couple of years, important because it let me find what else needed to be done.

Keep us posted on what you find.

Cheers Phil

 

[Mullaney]

Hi All,
Thanks for the suggestions. Shifting is gradually getting a bit easier, with practice. If anyone could post pictures of the pin that locates the shifter lever, that'd help. RPM level is about right, I think. Here's a new but related question: In 4th gear, something feels wrong, it feels like the clutch is slipping.. the truck just doesn't respond like it should. No sign of that in gear 1, 2, 3. But why would the clutch slip only in 4th? I'd expect slippage in low gears, which have higher torque. Maybe it's not clutch slippage I'm feeling? Something's wrong in 4th. Suggestions?
THANKS!

.
Definitely agree with @CMPPhil ...

Slippage of the clutch happens in the higher gears first. Accelerating up hill, you will hear the engine speed up and you will smell that burnt clutch smell eventually...

 

[Lumbar Jack]

.
Definitely agree with @CMPPhil ...

Slippage of the clutch happens in the higher gears first. Accelerating up hill, you will hear the engine speed up and you will smell that burnt clutch smell eventually...

Phil and Mullaney,
Thanks for the excellent advice, much appreciated. I'll try to get a look at the clutch and clean it off.

 

[Lumbar Jack]

Got the clutch pan off today. Lots of black dust in there, I haven't cleaned off the disk yet, but I suspect there's a new clutch in my future.. Where can I buy the parts? Does anyone offer a kit? Thanks!

 

[CMPPhil]

Hi

Try www.vintagepowerwagons.com they list them I think.

 

[fasttruck]

Clutch pedal has the specified free play listed in the TM? The M 37 here is distinguished by having fairly short gear lever throws' when moving front to back like between 3rd and 4th gear. However, the neutral gate is so wide you think you are pushing the lever out the passenger's door when shifting from 2nd to 3rd gear. Any synchronizers in the transmission don't work very well so I usually double clutch mine for all moving gear changes.

 

[Karl kostman]

I have ordered or should I say TRIED to order parts for Vintage over the last 6 months and they have been out a whole lot of stuff, Great guys but having a bit of trouble. I have been using Midwest Military as a very good backup and John has never let me down!

 

[Mullaney]

I have ordered or should I say TRIED to order parts for Vintage over the last 6 months and they have been out a whole lot of stuff, Great guys but having a bit of trouble. I have been using Midwest Military as a very good backup and John has never let me down!

.
White Owl in Kenston NC is another possibility for older parts and equipment.
They know and understand these trucks well enough to talk by phone and help you get the right parts.

 

[OutpostM37]

.
Definitely agree with @CMPPhil ...

Slippage of the clutch happens in the higher gears first. Accelerating up hill, you will hear the engine speed up and you will smell that burnt clutch smell eventually...

When I purchased my '63 M37, it was a mish-mash of parts from other trucks. Mine had a crash box from a 1 ton Dodge in the truck. See photos with cutout in floor board and transmission. Yours should have the NP420 (New Process) which is synchro'd in 3rd and 4th gears. I have a pic of the NP420 transmission with a red arrow showing the pin. I believe that on some early 420's there was a pin on only one side? Maybe someone can confirm this. Hope this helps.

 

[Lumbar Jack]

When I purchased my '63 M37, it was a mish-mash of parts from other trucks. Mine had a crash box from a 1 ton Dodge in the truck. See photos with cutout in floor board and transmission. Yours should have the NP420 (New Process) which is synchro'd in 3rd and 4th gears. I have a pic of the NP420 transmission with a red arrow showing the pin. I believe that on some early 420's there was a pin on only one side? Maybe someone can confirm this. Hope this helps.

Many thanks for those pictures, and for everyone’s advice, much appreciated. I took the bell housing off the clutch, intending to clean the friction surfaces with brake cleaner. But I can’t really see what’s going on inside the cover, can’t see any interface to be cleaned (with or without pressing clutch pedal). Around the perimeter I can see black crumbly material, like charcoal, presumably the edges of the friction disk? Three pictures attached.

 

[Roller]

The later transmission had two pins in the shift tower.

Frank

 

[GopherHill]

It's replacement clutch parts time. Looks like the friction disk has come apart. Things will be better after this repair.

 

[OutpostM37]

It's replacement clutch parts time. Looks like the friction disk has come apart. Things will be better after this repair.

X2 on the disc disintegrating. Buy the kit that includes the pressure plate, disc and throw out bearing. Your flywheel will most likely need to be resurfaced. Don't cut corners, do it correctly once. That way there is smooth clutch engagement and pedal feel. This jack worked great on the removal/install of my NP420 transmission of the M37.