980B driveline vibration

[Cmark]

I've never seen that chart before. I would imagine they would put 23.5 on a 980 so Mickey Rooney could reach the first step on the ladder Is that and A model or B?

I got it from the OMM for a 980B. I can't see it in an OMM for a 980C so we have to assume it applies to a straight 980 (no such thing as an A) and 980B. I wouldn't think there's anything stopping someone fitting something other than 29.5s on C and later machines, apart from the fact that it would mess up the speedometer readings.

 

[Nige]

Well judging by the photos you've found the first thing that needs to be eliminated as a possible cause.
Heed John C's words about lifting the front wheels off the ground to get rid of potential wind-up before loosening any u-joint bolts.

Also back to Cmark's suggestion regarding taking a good look at any play in the rear axle trunnion support bearings. It can be done using the machine but maybe better to jack up the rear end slowly while someone watches for movement in the location shown by the arrow in the photo below. You're looking for movement between the nose end of the differential (inside) and the support (outside with the ring of bolts in it). Note this photo is NOT from a 980, your machine may differ slightly physically but the principle is the same.

 

[oarwhat]

We have 4 980B's. Two have 26.5 x 25's and 2 have 29 x 25's.

 

[ssrider]

Thanks for the tip on releasing any driveline preload. So a few of you have warned me that the rear yolk is a slip on and can fall off. Is there any reason that I can not just pull the yolk off before test driving without the rear driveshaft?

 

[John C.]

We always called the straight 980 an A model to prevent confusion around here. You can check for play in the rear axle trunnions just by backing up slow and suddenly hitting the brakes. The axle will rock in the trunnions making a bumping sound and you can see it from the cab.

 

[kshansen]

We always called the straight 980 an A model to prevent confusion around here. You can check for play in the rear axle trunnions just by backing up slow and suddenly hitting the brakes. The axle will rock in the trunnions making a bumping sound and you can see it from the cab.

Agree on the "A" designation for just about all Cat equipment. I've always done the same thing, guess it's just easier that having to type out "Plain 980" or "Original 980" or what ever!

Another thing that may show up in the "fast stop test" could be loose center pins and bushings. There are a lot of "normal" bumps and jerks that someone who has been around these machines could see by a very short time in the cab. They sure could do all kinds of things when things get worn a bit!

 

[Cmark]

Is there any reason that I can not just pull the yolk off before test driving without the rear driveshaft?

The oil will start running out. (If it's at the correct level)

 

[kshansen]

The oil will start running out. (If it's at the correct level)

And dispite what one of my bosses believed, long story there for another time, if oil can come out dirt can get in. That is not a good thing for those bearings on the pinion gear and elsewhere in the axle.