973 Straight drive

[BRHol]

Hello members,

I'm not a native speaker but I'll try my best.
I have an question about a CAT 973 ser. nmbr. 66G
The machine is strong and runs very well, unfortunately it drives not straight. It pulls to the left when driving straight (no steering pedal touched) I have to slightly press the right steering pedal to keep m straight. engine and transmission heated up and oil levels and filters are ok. In reverse it is more or less the same.
Is this normal for its age? and if not, what can i do about it? Is it possible to adjust the speed of the drivemotors individual?

Best regards,

 

[Nige]

You need advice from the Cat hystat loader expert @Cmark hopefully he will be along shortly.

 

[BRHol]

Ok thanks, hopefully Cmark knows

 

[sealark37]

The first place to check is the steering pedal pivot bearings. If corroded, these pivot bearings restrict the full range of motion for the pedals. The bearings are cheap, but it can be involved to replace them.

 

[BRHol]

Thanks for the advice.
I've placed new steering pedal bearings in the linkage, steering works much better and smoother now.
I was not be able to check the straight drive yet, I'll come back later if this was the solution

 

[nicky 68a]

Just finding someone that’s experienced enough to diagnose any traxcavator that’s hydrostatic that drives off in a curve is a major problem in it self.It’s also expensive to diagnose and repair.

 

[John Shipp]

I am no expert, but have experience of a D8H 68A tracking not straight. We verified that the sprockets were turning at same speed by marking with chalk and driving forward for a distance without touching any steering lever = chalk lines were still lined up.

We messed around measuring track alignment which seemed ok. We measured track wear, but we didn't believe that different wear in the tracks would make it track on such a curve. However, we swapped the tracks side to side and it then went on a curve the other way. We bought new matched length set of track chains and it drove straight.

So I would want to verify whether the sprockets are turning at same speed first, if you haven't done that already.

 

[ih100]

Just finding someone that’s experienced enough to diagnose any traxcavator that’s hydrostatic that drives off in a curve is a major problem in it self.It’s also expensive to diagnose and repair.

Not always. It can be as simple as requiring the hystat system to be calibrated, and that can be done through ET. Mind you, that doesn’t apply to the older hystat machines.

 

[Nige]

To be honest, once it was certain that the linkage was moving smoothly and everything was correctly lubricated, the next step for me would be to make sure the linkages were all correctly adjusted before moving forward. See the attachment.

 

[pittsburgh cat man]

A 66g does not have any electronic calibrations. every thing is hydro mechanical. The first thing I would do is locate the two speed valve it will have a t with two small lines one going to each drive motor cap lines off and see if it will track straight. By the way it will be very slow

 

[Nige]

Welcome to the forum.......!!
Anyone with expertise on Cat hystat loaders of any generation is always welcome.

 

[Nige]

To be honest, once it was certain that the linkage was moving smoothly and everything was correctly lubricated, the next step for me would be to make sure the linkages were all correctly adjusted before moving forward.

It goes without saying that the whole linkage should be inspected and any worn pins, spherical bearings, etc, etc, all replaced before starting on the adjustments.

 

[Mobiltech]

The straight travel on a 973 can be adjusted on the linkage that is internal under the top cover of the trans. There are plugs that have to be removed in the cover and then you use a 1/4 inch extension to reach in and adjust. You will need to study the testing and adjusting for transmission calibration to do this properly.
I would normally say you need to find a mechanic who is familiar with the adjustment process but I Think you would have a hard time finding one.
This is easy to do and doesn’t require any fancy tools.
The last one I did was probably 20 years ago.

 

[pittsburgh cat man]

I'm not big on jumping on adjusting nuetral and sync screws. A lot of things need checked first. Pull clevis pins on steering linkage at hystat notice free play on leavers then you will feel spring tension on levers pins should go in while its in free play range next check brake lever on main control valve with cab down there is a hole in lever and a threaded boss on valve a 5/16 bolt should screw in. L ast if some one could come up with a cat form number senr3193 it would be a big help for you . lastly word of caution 973s are the only ones I've had try to move with brakes in test postion be careful