8N Mowing Problem?

[WI Dave]

I've been using my 8N to mow again with a 5' finish mower, after 2 years of it being "semi-retired". It's a 1952, still 6-volt, it starts easily, and runs good. I mow in 2nd gear, and it takes well over 3/4 throttle to get it to 540pto rpm, so I tried it in 3rd gear, and it was at 540rpm well UNDER 3/4 throttle. The tractor doesn't run rough, or smoke, and it's not bogging down, but I can't mow in 3rd gear. It'll bounce the tractor apart, or bounce me off the tractor! It had a broken governor back when I bought it, I put a new gov. assembly from nnalert in, and it worked fine. Any help or suggestions are appreciated.

 

[R Geiger]

I run about 3/4 throttle to get 540 PTO rpms regardless of what gear I am in. PTO rpms are tied to engine RPM, not what gear you are in. Only difference I see is that the different gears lug the engine down a bit differently. Seems to me a higher gear would lug engine down more requiring a bit more throttle in some conditions. IMHO

 

[WI Dave]

I was almost at full-throttle yesterday in 2nd, but in 3rd gear, it was closer to 1/2 throttle.

 

[R Geiger]

Do you have a Sherman gear box in it?

 

[Tom N MS]

Rough ground U need to be in 2nd gear anyway.

 

[WI Dave]

It's got a Sherman Combination tranny. It's in "standard" gear range.

 

[Jess Pidlin]

I don't understand different RPM with different gears and the [u:5855460505]same throtle setting[/u:5855460505]. As has been previously stated, RPM (revolutions per minute) is a measurement of [i:5855460505]motor[/i:5855460505] speed and has nothing to do with the transmission.

I mow with a '51 w/sherman over/under in 2nd, switching to 1st for tall stuff with the same throtle settng (which is approximately 3/4 open).

Something sounds funny with 3rd gear.

Jess

 

[DON TX]

I can't mow in 3rd or I get bounced out of the seat. Maybe because I weigh 145 soaking wet. 2nd full throttle is as fast as I want to go. Thick stuff may take me down to 1st uphill. HTH
DON TX

 

[R Geiger]

A Sherman in stepdown WIll reduce PTO Rpms and you would need more throttle to get the 540 PTO setting. That said I don't know what is going on with yours.
Good Luck

 

[WI Dave]

I know the engine speed determines pto rpm's, and trans. gear doesn't matter. That's what's strange about this!

 

[Jock (OR)]

The "throttle" lever is actually a governor RPM control. If you have it set in the same place, the governor will try to keep the engine RPM's at that speed. 3/4 on the quadrant should always result in the same engine speed. The governor will change the throttle setting in an attempt (sometimes unsuccessful) to return to the RPM setting selected.

How are you determining the PTO speed? It is highly unlikely that the PTO output speed is the same while the "throttle" quadrant is in a different position.

 

[jackinok]

fyi 3/4 throttle IS the proper position on quadrant for operating your pto at 540 .thats where it should run at and be operated at for most things.dont believe it? check your proof meter and see if 1500 - 1550 or so rpm doesnt =540 pto rpm.NOW IF you have a aux transmission,it depends on how its set,high,low, standard etc as to what pto rpm speed you get at what engine rpm.IF, and this is what its there for,you can get 540 pto rpm at half throttle with aux in high,and have power to mow then you'll save fuel.thats what a sherman and nearly ever other aux transmission was designed to do ,save fuel by lowering engine rpm..keeping pto rpm up to run equipment and still matching ground speed to terrain.

 

[jackinok]

how exactly are you determining pto rpm?in std gear throttle should not change to keep same pto rpm.it will however change in either step down or step up,are you positive your in std? center (nuetral) position on shifter,pull out to the left side of tractor and then back.are you sure sherman is shifting?if a fork was broken or something in sherman, shift lever "may" move and not change gears internally (maybe???)i think i would put sherman in high,then shift it to low and see if ground speed changed,if not thats likely your problem.other than wear in linkages i dont know what else would change,wear could make it flaky for sure,check for side play on gov arms.a lot of play there makes a lot of difference but you should notice that on engine rpms as much as pto.governor worn internally might cause that also but they ,at least the one ive seen, tend to hang and then jump loose when balls move and engine will rev suddenly on its own.