PTO neutral on M51A2

[Seq]

I can't find neutral on the PTO on my M51A2. I've removed all the linkage and can move the upper and lower shafts (not the output shafts) in and out but nothing keeps the rear output shaft to the hydraulic pump from turning. I can get the front shaft (for non-existent winch) to stop. I took the inspection plate off the PTO and everything seems to move freely. What am I missing?

I just became aware of this as I was replacing the u-joints on the shaft to the hydraulic pump. Pump is leaking bad and needs to be replaced.

 

[holley68]

The neutral position is one click down from the top.

Mine did the same thing. It is a residential spin. It will stop when there is resistance, say from a PTO shaft.

 

[Seq]

It still spins when hooked up to the hydraulic pump.

What do you mean by one click from the top? There are 2 shafts that move in and out of the PTO housing. One on top and one on the bottom. The one on top only move maybe a 1/2" in and out with a definite click. The bottom one slides 4-5 inches back and forth. I can feel it engage gears (and saw it when we took the cover off).

 

[gringeltaube]

See below diagram....

Unscrewing 5 cap screws (#37) is all it takes to remove the whole rear auxiliary drive unit and take a look inside.
It should come off easily; if not then the front nose of the output shaft (#40) could be stuck in the corresponding shaft assembly #4 and that would already explain your issue.
Otherwise check for a loose set screw #55; a bent shift fork #54 and a full 1/2" travel of the shift shaft #47.

 

[holley68]

Sorry, I misread your problem.

 

[Seq]

I'll take if off and take a look.

 

[holley68]

Your rig looks nice. Are those 16s tires. I need to change my tires, trying to decide what to do. How is your speed with those tires?

 

[Seq]

Tops out just under 60

 

[holley68]

Have you loaded it down? I normally haul but nothing to heavy most of the time.

Oh, you have the Mack. The old multifuel might not have the ability your does with the 52s.

 

[Seq]

Have you loaded it down? I normally haul but nothing to heavy most of the time.

Oh, you have the Mack. The old multifuel might not have the ability your does with the 52s.

Hauled 5 yards of drain rock last week. Wasn't bad except for 1 big hill. Need another gear between 3rd and 4th.

It's got the LDS, not the mack.

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[Seq]

And here she sits until I get a new hydraulic pump and figure out my PTO problem.

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[gimpyrobb]

I know I'm late to the party. Pull the auxiliary pto off the back with the 5 bolts G pointed out. Its a self controlled unit that shouldn't rely on the main pto. Also, try starting out in low range, shift through the gears, pull up 5he Tcase to high range and hit 4th and 5th again. Its like a 7 speed.

 

[Seq]

How difficult is it to replace the shaft and shift rod seals in the PTO? Figure I might as well get that done while I have it off.

 

[gringeltaube]

How difficult is it to replace the shaft and shift rod seals in the PTO? Figure I might as well get that done while I have it off.

Not difficult at all!
Maybe read this old thread showing seal numbers. Also post #8 in that same thread. (much easier to change seals and dust boots with the shaft removed, of course.)

The correct seal for the rear (aux.) output shaft would be Timken #254287 (1.25" hsg.bore; 7/8" shaft diam.; 0.25" seal width).

 

[holley68]

Seq, I thought it was a Mack because that is the air filter setup (teapot) for them.

 

[Seq]

Got it all apart tonight and figured out my problem. Just wasn't pulling the shift rod back far enough. Pulled to 1st click and figured that was it.

I'm assuming the aux shaft needs to be pressed out.

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[fasttruck]

Reference post 15: a M51 is gas, a M51A1 is the ENDT673 Mack, the M51A2 has the multifuel engine. Same suffixes for the cargo trucks and tractors. Depending on the engine, a direct drive or overdrive transmission would be furnished, otherwise they are identical except for parts that hook up to the engine as the accessories are in different places.

 

[holley68]

The teapot filter setup was for the Mack, per members of this forum. My M51A2 does not have the teapot. That is what made me believe it could have been a Mack. The orginal poster also stayed the engine was replaced, in his recover post of the truck.

 

[gringeltaube]

Got it all apart tonight and figured out my problem. Just wasn't pulling the shift rod back far enough. Pulled to 1st click and figured that was it....

It really shouldn't be able to move-in much past that 1st notch. Could it be that the retaining snap-ring #53 is missing? It goes in the groove, in the splined end of shaft #4 and stops the shift collar #38 before it bottoms out at the end of the splines, on shaft #4.

I'm assuming the aux shaft needs to be pressed out.

Well, yes - if you mean the output shaft #40 - because that makes it easier to replace the seal.
But don't forget to remove either retaining ring #39, before going near a press...!

 

[Seq]

Thanks, I'll have to take a look tonight. It does seem like that collar moves too far forward.

Any idea if the boots on the shift rods would be available at a local parts store or are they a specialty item? I figure I can get everything else locally (seals & gaskets) and am hoping to have this put back together by the weekend.