Discussion in 'Early CJ-5 and CJ-6 Tech' started by garage gnome, Mar 17, 2019 at 9:31 AM.
Which gear would give the PTO a speed of 540? I’m assuming it would be first gear.
Well, that's going to depend on the engine speed and the transmission gear ratio...
I read The gears in the rear housing are also interchangeable so your ground speed can vary a little to the PTO.
Going by the FSM, 2,000 rpm for the F-head and 1st gear gives 536 pto rpm. It doesn't mention which T90 1st gear ratio but the manual is from '69 so it could be the lower, T90-C.
I figured there would be a bunch of variables involved. I have a shaft tachometer I use for my engines, so I’ll check it with that.
Just curious, why the 540 rpm needed, what u powering?
Whatever I want. That’s the optimum speed for running any pto driven implement.
I would like to put a finish mower on eventually.
Per JW60's post you have to take into account the reduction ratio, if any, of of the rear gear box. Some do, some don't.
540 rpm is the standard rpm for measuring power per SAE, other than that I'd expect there's a fair range of speeds most things will operate at.
If my memory serves me correctly, the rear pto gearbox has 2 gears of different tooth count which can be installed in either position to give a slight underdrive or overdrive (relative to the input shaft rpm) depending on application.
Found ground speed/rpm/gear/range charts over on the CJ2A Page. These charts are based on the 20 and 24 tooth gears in either setup position.
Unusual Rear PTO Gearbox
Have a link on FarmJeep.com to this site Willys PTOs Lots of good info.
Not to hyjack, but anyone know of a rear mount garden tiller?
I've used that page several times when trying to determine what model of pto I have. Very useful! I would love to get a governor for my cj5.
I would start by searching craigslist.......
I had my finish mower hooked up to my old 62 and i want to say i putzed around in 2 low with no problems. Only drawback is you need a big field to work good. The turning radius on the cj's isnt the best.
A zero turn mower it's not
Here’s the jeep at an idle. The pto spins around 175 rpm. Guessing the gears are setup for the under drive which is perfect.
And here it is revved up. I had to switch scales. It’s turning at 750 rpm at half throttle at the engine.
When you die can I have your tachomete?
Found it on eBay.
I did some math and determined that the values listed on the chart I posted a link to above are for a T90A transmission with gear ratios of 2.79, 1.55 and 1.0, 1st, 2nd and 3rd, respectively. A T90C has lower 1st and 2nd gear ratios so pto shaft speed will be lower, as well as ground speed, for what it's worth.
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