4x4 lead/lag stress on drivetrain...what's the dif

[RickB]

For Woodbeef

I am a professional mechanic at a New Holland dealership. I have attended New Holland, CaseIH, Kuhn, and Gehl service training over the last 9 years. One of my current projects is a NH8670. Previously, I operated farm equipment and tractors up to 200hp with MFD. I don't know everything, but I am on firm ground here.I did not dispute the perils of mismatched tires on the same axle. Matching loaded radii to original spec will eliminate lead/lag related problems, period. Different brands or tread style WILL NOT cause driveline wind-up if selected properly; using tires with the incorrect loaded radius will. You should realize we are saying substantially the same thing!

 

[RickB]

Re: 4x4 lead/lag stress on drivetrain...what\'s the dif

Not absolutely sure, but I suspect the TC's have a small lead ratio, for the reasons stated in my original post.

 

[CTyler]

Re: 4x4 lead/lag stress on drivetrain...what\'s the

Just my thoughts...
It seems lead would be easier on the drive train than lag. With lag your essensialy trying to turn the front wheels backwards while your driving forward. Obviously they are not going backwards but its the same effect to a much lesser degree.

With respect to the last post on NH. If its auto sensing it probably doens't matter, with respect to drive train wind up, since there is a desparity in tire speeds anyway. There is obviously pleny of give in that situation.

 

[BillyP]

Re: 4x4 lead/lag stress on drivetrain...what\'s the

One other thing to remember. Keep the tire pressure where it should be. This is more important on a MFWD, since it affects the lead/lag of the front tires. Low front tire pressure causes the front tires to lag. It's just like having mismatched front tires.

 

[thcri]

Re: For Woodbeef

Ok Rick,

I got a good question for you. TC29D with Supersteer Auto Sensing. When I rapidly turn the steering wheel sharp to make a tight turn I will rip up the grass with R4's. But if I make that same turn but gradually turn the steering wheel to make the turn I will not tear up the grass. My comparison would be going at the same speed just turning the steering wheel faster or slower. In other words if I prepare more for the turn my turning ealier I won't rip up the grass.

Now if you tell me Im goofy, for the most part I would believe you. I didn't believe myself until I learned with supersteer that you have to turn that way. Is it because sensi-trac is kicking in?

Murph

 

[Woodbeef]

Re: For Woodbeef

Hey RickB,

True we are both basically saying the same thing on the tire size aspect I guess you could say in the long run.

But as for the number of lugs,I've seen it happen with 3 different tractors. First was a mfd CIH 1494,that was bought used and dealer threw a better front tire of the same size,but different make on the front. Tractor had a noticeable binding feel to the drivetrain in mfd. Dealer went over tractor top to bottom trying to find problem. Retired mechanic stopped by one day for a chat,and spotted it right off. 3 more lugs on on side of axle. Dealer swapped both tires for a matched set. No problems after that. Then I saw it with a mfd Ford 8600,and a mfd JD 3140. Informed owners about the tire differences,once matched ones were put on,problem disappears. Now like I said earilier might only be certain brands. Both the Ford and the Deere had a ZF axle. Not sure about the CIH might have been either a Dana or a Carraro. So you're saying that it was the size of the tire not the amount lugs that made the difference? Could be possible. How much out of spec then would make this difference do you figure?

 

[RickB]

Sensitrak

I haven't had an opportunity to fiddle much with the sensitrak clutch, but here's what I <font color="blue"> THINK </font> may be happening. Steering angle determines the amount of tension applied to the clutch via a cable. When you turn abruptly, the spring-loaded cable puts pressure on the jaw clutch sooner in terms of feet travelled than it does if you steer gently. The further you travel around a curve in 4WD, the more the driveline 'wraps up' Steering sharply allows the cable to disengage the clutch before it is bound up by driveline windup. Steering slowly allows the clutch to be bound up to the point where the external spring stretches rather than pulling the jaw clutch apart, disengaging the axle. The short answer hidden in this long post is try adjusting the cable sheath AWAY from the clutch to pull the spring more, and disengage the axle sooner.

 

[RickB]

Back to Woodbeef

Yes, my experience is that it is all about radius. We may also be talking about two different problems. I was thinking more in terms of driveline windup. You may be, too, but the idea of having one new tire on the front causing problems also could be related to a limited slip differential. ZF and Carrera use a limited slip diff in many applications. These can be noisy and aggrivating as the diff loads up and slips. I believe these symptoms would also relate more to radius than anything else. Putting new tire(s) on the front OF THE PROPER SIZE could also shift the lead ratio into the trouble zone if the rears are worn enough. Seems to me anything over about 7% lead will cause noticable handling characteristics. I have driven New Holland compacts with turf rears and ag fronts that performed well. I also installed new turfs of the proper size on a 1720 with worn turf rears and had trouble disengaging the front axle due to wind up. I had to inflate the rears and deflate the fronts nearly to extreme to get the tractor to perform just barely to my satisfaction. Of course, the owner did not want to hear about replacing the rears, which would have cured it. (I wouldn't have either) Most problems start with the replacement of fronts which increases the lead ratio. if rears wore out quicker than fronts , there would be less of these problems.

 

[thcri]

Re: Sensitrak

Rick,

So in other words, Im not goofy then. This really is happening.

 

[RickB]

Re: Sensitrak

I can't tell for sure whether or not you are goofy, or how much. I can tell you the TC is not a major contributing factor!