4.0L Engine Revs and Rear-End Quiz...

[Jim Cissell]

Recently I had my tires 'trued' by a local tire center. They recommended the procedure due to some scalloped wear on the tires. While up on the rack, they said they needed to take the tires to 70 MPH to provide a quality balance. On the front tires, they used an electric-motor wheel spinner to do the trick. On the rear set, they simply put the Jeep in gear and rev'd it to the proper 'speed'. As many of you know, this spinner-device had a blade that trimmed the tires to true.

My first question is, did taking the engine to the RPMs required to simulate 70 MPH put the engine in a potentially damaging situation? I don't recall the revs sounding too high, but I was wondering if they had to push it in the 'high zone' to get to the 70 MPH?

My second question concerns an odd 'groaning' sound produced during the spinning of the rear-end. The technician said it was 'gear clash' due to the rear-end not being under load while spinning that fast. It didn't sound terrible, but it was indeed a noise that I never heard before, and was troublesome to me.

Is this so-called 'clash' normal under such a situation, and more importantly, was it a signal of a gear-damaging situation on my Dana 35 rear-end?

Thanks for your insight into these concerns...
Jim

 

[Curious Kid]

As far as rev's, nothing more than if you were to drive the vehicle on the road at 70 mph - it's geared.

Concerning the odd noise, the logic seems right in that it would sound different as the diff is not under load and thus "oil film-mesh play." I can't imagine such a short run would cause anything to come of it.

This whole procedure of truing is something new to me. Aside from the scalloping, were you experiencing any straight-line driving issues that lead one to think this procedure was required.

 

[Greaser]

If you read your owners manual spinning axles over a certain mph (60 I think)with-out load will damage your gears.These guys sound like Larry,Moe,Curly had girlfriends in AL. and mating was succesfull

 

[Jim Cissell]

Where exactly in the manual does it say not to spin the rear-end over 60 MPH without a load? What kind of damage do you think will occur?

Thanks,
Jim

 

[Greaser]

quote:

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Originally posted by Jim Cissell:
Where exactly in the manual does it say not to spin the rear-end over 60 MPH without a load? What kind of damage do you think will occur?

Thanks,
Jim

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I could run out to my Jeep and get the exact wording (somewhere in driving in snow & spinning wheels or off-roading section)from the owners manual but can't leave my computor right now.Causes severe heating of bearings and gear faces.Post a question on here about this (excessive wheel spinning) and see what happens?I've seen people spin their tires trying to get up a rock face on Jeep Jamboree's till all you could see was a blue cloud of tire smoke...kiss that axle good-bye in a couple of months..My hunting partners' Dana 35 on his Grand Cherokee bit the dust due to someone spinning the snot outa it...

 

[Jim Cissell]

Does no-load spinning effect the gears more negatively than under load?

 

[Greaser]

quote:

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Originally posted by Jim Cissell:
Does no-load spinning effect the gears more negatively than under load?

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I'll post the question for ya

 

[medic]

I think that may be a different situation, where only the wheel with the least amount of traction is spinning, while the other is not moving. In this case, both wheels are spinning and there is no load at all.

It sounds like they are balancing the tires on the vehicle. Instead of using lead weights, which may be knocked off or fall off, they are removing rubber. It makes sense to me, but I have never heard of this before and I am not going to advocate this practice without reseaching it first.

 

[Jimbo]

The owners manual warning assumes that you are looking at the spedo in the dash and have one drive wheel stopped. The spinning wheel is turning twice the indicated speed. 70 mph at the tire is no problem, 140 on an all-terrain tire might be, but without any load on it, probably not. You did not state that they "locked" one wheel and let the other one spin.

Jim

 

[Greaser]

quote:

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Originally posted by XS650:

quote:

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Originally posted by Greaser:

quote:

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Originally posted by Jim Cissell:
Where exactly in the manual does it say not to spin the rear-end over 60 MPH without a load? What kind of damage do you think will occur?

Thanks,
Jim

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I could run out to my Jeep and get the exact wording (somewhere in driving in snow & spinning wheels or off-roading section)from the owners manual but can't leave my computor right now.Causes severe heating of bearings and gear faces.

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That because when you spin one wheel, the spider gears spin like crazy. They are meant to either not turn at all (straight line driving) or turn slowly like when you are going around a corner. The spider gears and their bearing surfaces aren't intended for high speed operation.

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Thats what it was..my buddies spider gears were almost welded to-gether due to wheel spinning...we opened his diff cover and a grey paste came out..what a mess!He had a complete axle rebuild and it's fine now.I was told never to "air-spin" a set of bearings clean with an air compressor before repacking them, they can & will separate from their cages if spun to quick under no load.

 

[XS650]

quote:

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Originally posted by Greaser:
Thats what it was..my buddies spider gears were almost welded to-gether due to wheel spinning..

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It's not a bug it's feature. A free limited slip

 

[Greaser]

quote:

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Originally posted by XS650:

quote:

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Originally posted by Greaser:
Thats what it was..my buddies spider gears were almost welded to-gether due to wheel spinning..

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It's not a bug it's feature. A free limited slip

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Actually thats a way some guys get a cheap spool,welded spiders,but thats not what my friend wanted

 

[Jim Cissell]

I got pretty concerned, so I called the Dana Corporation and talked to the drivetrain division, technical info line, and told the scenario to the guy there. He said as long as there was a proper fluid level in the differential, there wouldn't be a problem on a no-load spinning situation such as this.

Jim

 

[Greaser]

quote:

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Originally posted by Jim Cissell:
I got pretty concerned, so I called the Dana Corporation and talked to the drivetrain division, technical info line, and told the scenario to the guy there. He said as long as there was a proper fluid level in the differential, there wouldn't be a problem on a no-load spinning situation such as this.

Jim

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Then you're probably allright.I was thinking of the one tire spin scenario from the owners manual and spider gear burn-out..sorry to give you a scare.Doing a little reading and a groan at high speed can be loose specs on a gear-set or a bad bearing.

 

[theguru]

I would be concerned as to why the tyres needed trueing in the first place.

Sounds like the shockers are not too healthy.

 

[XS650]

quote:

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Originally posted by medic:


It sounds like they are balancing the tires on the vehicle. Instead of using lead weights, which may be knocked off or fall off, they are removing rubber. It makes sense to me, but I have never heard of this before and I am not going to advocate this practice without reseaching it first.

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Some tires shops used to offer that service back in the olden daze (1950s). The cutting was just to true the tire and make it round. They still used balance weights to balance the tire. The story was that it took less weight to balance a trued tire. Probably true in most cases.

Truing might be worthwhile to salvage some wear out of a severely cupped tire, but if a new tire is out of round enough to need truing, it's a defective tire and you shouldn't buy it.

It sounds more like a scheme to get extra money from their customers and leave their tire tread on the tire Shop floor so they can $ell you new tires $ooner.

[ July 18, 2005, 12:28 PM: Message edited by: XS650 ]

 

[XS650]

quote:

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Originally posted by Greaser:

quote:

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Originally posted by Jim Cissell:
Where exactly in the manual does it say not to spin the rear-end over 60 MPH without a load? What kind of damage do you think will occur?

Thanks,
Jim

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I could run out to my Jeep and get the exact wording (somewhere in driving in snow & spinning wheels or off-roading section)from the owners manual but can't leave my computor right now.Causes severe heating of bearings and gear faces.

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That because when you spin one wheel, the spider gears spin like crazy. They are meant to either not turn at all (straight line driving) or turn slowly like when you are going around a corner. The spider gears and their bearing surfaces aren't intended for high speed operation.