PTO basic's?

[maineSS]

With respect to winch rpm vs engine gear, I don't think gear selection influences winch rpm on the OEM setup, it's engine RPM. The speed can be set with the hand throttle. The OEM PTO had a rating of 30 HP at 1700 RPM, and the output RPM differs according to whether the PTO output is turning the same direction as the engine, or counter to it (lower RPMs).

[712edf]

mo room fo mo mota!

I have to ask the question:

Why on earth would you want to downgrade your brake system from power to manual?

I want to "feel" the truck when I'm driving it.

I'm an odd duck.

Bucky

[712edf]

With respect to winch rpm vs engine gear, I don't think gear selection influences winch rpm on the OEM setup, it's engine RPM. The speed can be set with the hand throttle. The OEM PTO had a rating of 30 HP at 1700 RPM, and the output RPM differs according to whether the PTO output is turning the same direction as the engine, or counter to it (lower RPMs).

I was speaking about how my particular set-up operates. At a given engine RPM: higher transmission gear=higher transmission output shaft rpm's=higher t-case input shaft rpm's=higher pto rpm's. My PTO is off of the t-case. Some are not.

Yes higher engine rpm's=higher winch speed too.

Bucky

[MasterYota]

With respect to winch rpm vs engine gear, I don't think gear selection influences winch rpm on the OEM setup, it's engine RPM. The speed can be set with the hand throttle. The OEM PTO had a rating of 30 HP at 1700 RPM, and the output RPM differs according to whether the PTO output is turning the same direction as the engine, or counter to it (lower RPMs).

MaineSS - would you happen to know the pto rpm at 1700rpm on the engine? That would determine (for me) if the PTO adds any additional gear reduction to the winch drive system. If so, it could influence which transmission gear I select to operate the winch.

If I run my engine at 1700rpm while winching, I can set the PTO output speed from roughly 255rpm (1st gear) to 1700rpm(4th gear) with a corrosponding speed value for the other two gears. My concern would be turning the winch either too fast, and or, not enough gear reduction (via the PTO port) to make it pull accordingly.

Thanks for the Math guys, its all helping...

[maineSS]

There's a spec sheet at www.dodgepowerwagon.com/main/spec230.html that has some PTO stuff. It says that PTO rpm is 395 @ 1000 engine rpm, and the pto gear has 36 teeth. There are differing output rpms depending on whether the PTO is being driven the same direction as the engine (61/5% of engine RPM) or counter to it (47.5% of engine RPM) but this may apply to the side of the tranny the PTO is mounted on- left side is counter rotating, which would be the driverside if standard automotive practice is being used here. The output was listed as 35 Hp at 1700 rpm for rear tailshaft use. I haven't been able to find the gear ratio for the MU2 winch, but since it's a worm, the stepdown is substantial. If you know the number of teeth on the pinion gear, (say 20, for example), the ratio would be 20:1, as the worm is always 1.

[MasterYota]

So based on those numbers (with engine rpm at 1000, and pto rpm at 395) I presume that the PTO adds a reduction of about 2.53:1 to the winch drive system. This means that 2nd and 3rd gear in the trans should turn the winch at an appropriate speed without overwhelming anything. I have no idea what the HP would be at the front of a Tcase output would be. I'm going to presume its more than 30HP with a Big Block idling infront of it.

Is there anything like a fuseable link in the winch drive system (aside from ujoints or cable strength?). I'm wondering (as I'm not using a PTO box) if there are any shear pins etc... that I might need to design into the new drive system to keep it from grenading.

Thanks for the help guys, it looks like the PTO will be staying put at the moment.

[iranch]

pto basics

I think the ratios maineSS quoted are for the transmission mounted PTO. Transmission PTOs for winches are Bi-directional (forward-reverse) and always turn with the same relationship to engine RPMs, The forward side just engages a PTO gear to the cluster gear on the transmission, the reverse side has an additional gear in the drive between the transmission cluster gear and the PTO to get the reversal and because of size restrictions the ratio changes.

The transfer case PTO would have different ratios. Transfer case PTOs are usually single direction and depend on the transmission for reverse. Forward speed is a function of gear selection (1,2,3,4) and the ratio of the PTO.

I hope this makes sense for you.


Dennis

[Desoto61]

Is there anything like a fuseable link in the winch drive system (aside from ujoints or cable strength?). I'm wondering (as I'm not using a PTO box) if there are any shear pins etc... that I might need to design into the new drive system to keep it from grenading.

I just started tearing mine apart and the winch input yoke has a pin holding it to the worm shaft. It didn't look like a shear pin but it would be a weak link. You could probably install a shear pin there if you were worried about it.

[maineSS]

The winch u-joint has the shear pin- it goes thru the end of the winch shaft. Do NOT use hardened bolts for shear pins- you have a good chance of binding the worm and pinion "together forever", or splitting the case. The original shear pin is made of brass, and is carried by VPW.

[MasterYota]

Thanks alot guys!

Its this type of knowlegde that makes this place great! This was exactly what I was looking for.

Its good to know about the shear pin. I'll have to look into packing a few of them (or something comparable) in the boonie box just in case.

[maineSS]

I disassembled my MU2 for rebuild and found the pinion gear has 29 teeth- so the reduction factor is 29:1. The gears had sat in "miracle lube" (half 90 wt and half water) for who knows how long, allowing the worm to pit and really chew up the pinion. Now I'm looking for a good used set.

[MasterYota]

I disassembled my MU2 for rebuild and found the pinion gear has 29 teeth- so the reduction factor is 29:1. The gears had sat in "miracle lube" (half 90 wt and half water) for who knows how long, allowing the worm to pit and really chew up the pinion. Now I'm looking for a good used set.

Wow, that seems like such a minimal amount of reduction, I was expecting a ratio alot deeper than that...

Most newer winches are geared almost 10 times deeper than that, but I suppose they have alot less power to turn them if comparing apples to apples (being a 4-6hp electric motor vs. a 30hp pto...)

[maineSS]

You have two reductions, one being the PTO, the other being the winch. At the 395 rpm/1000 rpm tranny speed, you end up with 13.6 winch drum rpms @ 1000 tranny rpm (395/29), which is a 73.5:1 reduction. What is the typical electric motor rpm- all the reduction is being done at the winch, so a 1750 starting rpm will need more ratio.

[MasterYota]

As usuall MaineSS your math is spot on with your logic. Perhaps you can shed some light on a rumour I've heard as well. It goes something like this:

I've heard unsubstantiated rumours that the Military rated all their equipment to 50% of its civilian counterpart. In other words, a 3/4 tonne mill spec truck, would actually be rated as a 1.5 tonne truck in the civilian world. I've heard this is true for the winches as well, having been told that the M37 winch was rated at 7500lbs for mill spec service, but its actually closer to a 15000lb winch in real life. I would assume that this was done so that under battle field conditions, the GI's could get away with thinking they've overloaded a vehicle, but in reality its still be capable of performing its duty just fine.

Any thoughts? I keep looking at the MU2 and think that its just too big a winch to be rated at only 7500 lbs of capacity. If thats the case, has anyone out there found themselves in a situation where the winch hasn't been able to pull the truck out?

[712edf]

Seems like on other vehicles (civilian) the MU2 was rated at 10000lbs. Don't know who gave it that rating (Dodge, Braden?).

Bucky