Re-engine a 425?

Bob999 · Jan 3, 2005

When the oil gets very hot and your driving up hill, one or both front wheel will get spinning and the rear wheels don't seem to be doing anything. It's like, cool oil= 4wd and hot oil+1 or 2wd. 

Can anyone offer an explanation why oil at an elevated temperature, and presumable thinner, would drive the front wheels but not the back wheels?

I have observed that on steep hills the front wheels are the first to spin but always assumed that was because the weight shift to the rear when climbing a hill, combined with the weight of the engine, simply loaded the rear wheels more than the front and gave the rear wheels more traction.

bubenberg · Jan 3, 2005

One question is is your attachment engaged or not when your front tires are slipping. Cure lift the attachment or disengage your action and the slipping should stop.

We found this out during our four winters of sometime high snow, when we had to start to plow coming off the 20 foot trailer, that we needed more traction. By only moving part of the height of the snow we reduced the slipping of the front tires. /forums/images/graemlins/grin.gif

good luck

Bob999 · Jan 3, 2005

One question is is your attachment engaged or not when your front tires are slipping. Cure lift the attachment or disengage your action and the slipping should stop. 

Hans,

You may recall I have an 1845 with draft control. I use the draft control at all times and still get the behavior I described. My assumption is that the back wheels carry more weight even with the draft control when moving up a steep hill (greater than 20 degrees).

johara1 · Jan 3, 2005

i put chains on the front.ended all bad things. remember that a pt is a loader,like all loaders you put them in float they tend to ride up on the arms taking weight off the front....... /forums/images/graemlins/crazy.gif take it out of float and pick a little weight with the control and that will help. chains stop it all, front end spin,crabing,works for me /forums/images/graemlins/laugh.gif

MossRoad · Jan 3, 2005

The draft control should be taking some of the weight off the arms and transferring it to the front tires for him when needed.... I think /forums/images/graemlins/crazy.gif

Schultz · Jan 4, 2005

It sounds like the draft control isn't working properly, or maybe you could adjust it to pick up more weight?

FOURTEEN · Jan 4, 2005

"" While the oil tank on your machines maybe too hot to touch, that may not be too hot for normal operation. ""

The PT-425 far exceeds these recommendations !!!! Amsoil is specifically designed for Hydraulic use!! It is NOT Motor Oil!!

/forums/images/graemlins/frown.gif /forums/images/graemlins/frown.gif /forums/images/graemlins/blush.gif /forums/images/graemlins/blush.gif

Bob999 · Jan 4, 2005

It sounds like the draft control isn't working properly, or maybe you could adjust it to pick up more weight? 

The draft control works fine. My point was that even with draft control engaged and working that I get wheel slip on the front wheels before the rear wheels when going up hill. A previous post had ascribed this to hot hydraulic oil and I asked how hot hydraulic oil could differentially affect the front and rear wheels. No one has offed an explanation how that could happen.

The previous post was by RegL and said in part: Your correct as long as you don't include hill climbing as normal operation. When the hyd oil is cool all wheels seem to pull evenly and traction is good. When the oil gets very hot and your driving up hill, one or both front wheel will get spinning and the rear wheels don't seem to be doing anything. It's like, cool oil= 4wd and hot oil+1 or 2wd. I think the oil pt uses in the hydraulics looses it's viscosity at high temps and passes through the wheel motors under heavy load.

RegL · Jan 4, 2005

( It sounds like the draft control isn't working properly, or maybe you could adjust it to pick up more weight? 

The draft control works fine. My point was that even with draft control engaged and working that I get wheel slip on the front wheels before the rear wheels when going up hill. A previous post had ascribed this to hot hydraulic oil and I asked how hot hydraulic oil could differentially affect the front and rear wheels. No one has offed an explanation how that could happen.

The previous post was by RegL and said in part: Your correct as long as you don't include hill climbing as normal operation. When the hyd oil is cool all wheels seem to pull evenly and traction is good. When the oil gets very hot and your driving up hill, one or both front wheel will get spinning and the rear wheels don't seem to be doing anything. It's like, cool oil= 4wd and hot oil+1 or 2wd. I think the oil pt uses in the hydraulics looses it's viscosity at high temps and passes through the wheel motors under heavy load. )

 I don't think I explained my point very well concerning PT performance with cool verses hot hyd oil.( Sometimes it's hard to type what I'm thinking /forums/images/graemlins/mad.gif. The front wheel spinning that you and I both described is correct when climbing forward. If you turn around and try to back up, you will find that the rear wheels will break loose first. clearly, what ever end of the tractor is pointing up hill has the least amount of traction.
The point I was trying to make is that when the hyd oil is cool, the wheels that have the most traction, and therefor the most load, will keep pulling and take you up the hill. When the oil gets to hot the wheel motors under the same load will stall. The uphill wheels will stall also if they have enough traction but usually they just break loose and spin.
The way my PT is plumbed, the front and rear wheel on each side is in series so the same fluid is running through both wheel motors. That's why I believe when the oil gets hot, it thins out to a point where it just passes thru the wheel motor with the most load with out turning it but can still spin the other wheel that doesn't have as much traction. I think the cure will be either better cooling or a different oil that doesn't loose it's viscosity at hotter temps.( I think it's refered to as viscosity shearing).
OK, I hope that was clearer. If not, maybe someone can read my mind and post it for me.LOL!

cqaigy · Jan 5, 2005

RegL

Well thought out post. Your logic looks to hold together. It seems that the thinner oil would flow thru the hydro motors easier providing less thrust. Also it would make sense that condition would also contribute to the heating of the oil.

I,ve seen similar effects even with directly coupled drives i.e. 47 CJ1 when climbing steep hills. You can see the front wheels slipping more then the rear wheels where there is more weight and traction. Even the effect is small it's still noticeable.

I have to say, it sure is interesting to read the PT forum. There are alot of very smart people contributing here and they do a good job reasoning and explaining things so that people like me can understand them.