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Discussion Starter #1
I’ve been looking through my X748 manual and can’t find the answer to this question. Does the rear PTO always turn at 540 regardless of engine RPMs, or does a 540 RPM PTO mean you have to be at WOT to get there?
 

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I don't know anything about X748s, but I can't imagine how JD would make a constant RPM PTO. So I'd bet it changes with engine RPM and needs to be WOT to run at 540.

Can you find someone to operate your tractor with something attached to the PTO and run it without a load? (Tiller lifted for example) Just watch while someone runs the throttle up and down and observe the speed of the attachment.
 

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The Magnificent
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Same as Leaon, I have no experience with x748s, but I have run a couple of New Hollands with hydrostatic trannies.

NH has a dandy little 540 RPM indicator lamp when the PTO is engaged. Also has an overspeed indicator lamp. 540 RPM on those TCs occurred well below WOT.
 

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Discussion Starter #5
Yeah, I'm pretty sure it is 540 at WOT. Didn't think about a non-contact tach. Thanks Harry. :fing32:
 

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Dont have my X yet but the JD 4410 tach shows a 540PTO icon at about the 2200 spot.
 

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Roy, I thought I remembered that there was a "PTO" indicator on the throttle. No?

Anyway, it definitely doesn't run at 540 regardless of engine speed. It should take the same (or nearly the same) engine rpm as for the mid/front pto. If there's no indicator on the throttle scale, then WOT is probably the answer.
 

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Yeah, I'm pretty sure it is 540 at WOT. Didn't think about a non-contact tach. Thanks Harry. :fing32:
Roy,

You just answered your own question.

Jerry
 

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Discussion Starter #9
Roy, I thought I remembered that there was a "PTO" indicator on the throttle. No? . . . .
Just went out to look and make sure. No indicator, just a turtle and a rabbit.
 

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Okay, I guess I was thinking of another tractor. Must be the hare, then.

One thing I have wondered about, is how they deal with PTO speed when they have different engines (gas/diesel) and different versions (your diesel/Minimax) that run at different rpms? Are they making some kind of adjustment in the transmission to correct for this?
 

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Discussion Starter #11
Okay, I guess I was thinking of another tractor. Must be the hare, then. . . .
Yeah, I'm thinking there is not a PTO indicator on the X700 series throttle because the rear PTO is an add-on. Any way, I ordered one of them fancy smancy non-contact tachometers, so it should answer the question when I get it. :fing32:
 

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For every tractor where I've seen it marked, 540 rpm on the PTO is achieved somewhere below WOT.
 

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Rabbit = @ 2,000 rpm mid-PTO, @ 540 rpm rear-PTO

The difference in gas or diesel engine RPM won't affect the PTO's enough for you to notice.
 

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Discussion Starter #14
Ok, I got me one of those non-contact tachometers (BTW, they are pretty cool) and run some tests. At WOT, the X748’s engine RPM is 3360 and the 540RPM rear PTO is turning 588 RPM! The PTO turns at 540 when the engine RPM is throttled back to 3100.

Since the X748 does not come with a factory installed tach, how and the heck are you going to know that unless you have installed an aftermarket tach?

So, if you are running a 540RPM attachment and the manual says “do not exceed 540 RPM” I guess you should throttle it back a little, or get a tach. :fing32:
 

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The Magnificent
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Glad you got it figured out, Roy. I guess for now maybe you can use a piece of tape to line the throttle up properly.

For what you gave for that x748, I would have expected a little more tech.
 

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Roy,

Thanks for the report. Good to know.

Did you try checking the pto rpm when it was under load, or just spinning freely?

Yeah, a tachometer is one thing I feel they really should have included on the X700 Series, right on the dash.
 

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Ok, I got me one of those non-contact tachometers (BTW, they are pretty cool) and run some tests. At WOT, the X748’s engine RPM is 3360 and the 540RPM rear PTO is turning 588 RPM! The PTO turns at 540 when the engine RPM is throttled back to 3100.

Since the X748 does not come with a factory installed tach, how and the heck are you going to know that unless you have installed an aftermarket tach?
Just ask here. :biglaugh:
 

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Discussion Starter #19
. . . Did you try checking the pto rpm when it was under load, or just spinning freely? . . .
I had a 3-point MacKissic Mighty Mac chipper/shredder hooked up when I did the testing. Wasn't feeding anything through the shredder.
 

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Ok, I got me one of those non-contact tachometers (BTW, they are pretty cool) and run some tests. At WOT, the X748’s engine RPM is 3360 and the 540RPM rear PTO is turning 588 RPM! The PTO turns at 540 when the engine RPM is throttled back to 3100.

Since the X748 does not come with a factory installed tach, how and the heck are you going to know that unless you have installed an aftermarket tach?

So, if you are running a 540RPM attachment and the manual says “do not exceed 540 RPM” I guess you should throttle it back a little, or get a tach. :fing32:
Good info Roy. :thanku: My non-contact tach was delevered but has not been used yet. A nice compliment to the Tiny Tach.:fing32:

Glad you got it figured out, Roy. I guess for now maybe you can use a piece of tape to line the throttle up properly.

For what you gave for that x748, I would have expected a little more tech.
Roy has added a Tiny Tach to Big Greene so does have engine RPM info available - no tape needed. :thThumbsU
http://www.mytractorforum.com/showthread.php?t=171364 with a cross post in http://www.mytractorforum.com/showthread.php?t=169137
 
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