963B Hydro/ Hydraulic acting up question

[Jon S]

Hi all,

I recently purchased a 1998 963B for general farm work (fencerow clearing, etc). Does anyone know what condition would cause the hydro to slow slightly while the boom/ bucket function is cycled under a load? I have not checked (or changed) the filters, but it was supposed to be completely serviced recently. The people that I bought the machine from claimed that the pressure tests were within specs when they tested it. I was told that the bypass valve may the issue, or that the linkage may be out of adjustment.

And, since I'm asking questions, the bolt that holds the equalizer bar pin in is broke off in the housing. So, does anyone have any tried and true tricks that they would like to pass on regarding removing the broken bolt? I thought about drilling it out or possibly welding a small nut onto the bolt and using heating and cooling to extract the bolt.

Any input would be appreciated.

 

[Daewoo]

I have seen the problem with the hydrostat dropping out/slowing down caused by the underspeed valve in the hydrostat (left hand side, attached to throttle control linkage). Drive forward in the machine and slowly reduce the throttle and see if you hit a point where the machine speeds up.

 

[Nige]

Regarding the broken bolt the best way is to get hold of a good welder and weld something on to the end of it to get it out. There was a thread about broken bolt removal on here somewhere not long back, and that was the concensus opinion.

 

[WhyWhyZed]

I have seen the problem with the hydrostat dropping out/slowing down caused by the underspeed valve in the hydrostat (left hand side, attached to throttle control linkage). Drive forward in the machine and slowly reduce the throttle and see if you hit a point where the machine speeds up.

^ agree
definitely want to do all the external linkage adjustments first. In fact, you want to check them any time the cab has been up.

Aside from that, slowing of the hydrostat is not completely abnormal, the to systems are powered by the same engine after all. If the engine lugs, the machine will slow down.

Also, if the hydrostatic charge pump is weak, the slowing of the engine could be dropping the flow to a critical level where the underspeed valve is starved.

 

[Jon S]

I'm thinking underspeed valve issue or linkage adjustment. It's definetly not your run of the mill engine lugging issue. I got someone coming sometime soon that knows more than I do to check things out. It's really not a big problem and certianly is not standing in the way of progress, just one of those nagging type things. Thanks for the replies.

 

[pushcat]

One possible easy solution would be to make sure the throttle is pulled all the way back in the wide open notch. 100-150 RPM makes a huge difference. We had the same problem with a 953, all pressures checked out to within specs. I was slot dozing and it would just stall out, got pizzed at it, slapped the throttle with my hand, it went back 1/4 inch and the machine just took off, full bucket and all. Might be worth a shot.

 

[dirtfarmer]

I too have just bought a 963 with a few issues. I want to ask questions but since I just joined this site I have to post 3 times before i can create a new thread so I am replying to yours. Good luck with your cat.

 

[Daewoo]

Jon S....you still around? I would be interested to hear what ended up being the problem.

 

[dirtfarmer]

Yes, I hope someone tells what they found out because my 963 doesn't even try to move at the moment but I haven't had time to look into it yet. It has way too much oil in the gear-case and it's low on oil in the transmision. Is it posible for the trans to leak or blow oil into the gear-case(behind the motor)?

 

[Jon S]

Sorry guys. The CAT expert never showed up, so I basically went through the linkage adjustments and it seems to be working fine now.

 

[Daewoo]

Dirtfarmer,

It is possible, but not really likely...and you want to eliminate all other possibilities before you jump to that (trust me on this...pulling the hydrostat is a pain).

What exactly is it doing? Does the motor change at all when you put it into gear? Do the hydraulic systems work?

 

[Sunesis1]

At least the simple adjustments curred your problem. Great News!!!

 

[Daewoo]

Just FYI, I have a full set of service manuals on this machine, so if you need anything out of it let me know.

 

[dirtfarmer]

If you are talking to me about the manuals-----thank you. I will keep it in mind.

 

[Daewoo]

Actually it is for anybody who might need some information out of it or a few pages scanned.

 

[detroyt]

Just FYI, I have a full set of service manuals on this machine, so if you need anything out of it let me know.

I would love to know where all the filters are located

 

[dirtfarmer]

I finnally got time to check out my 963 and after a long process of elimination, I found out that the center foot pedal "the o-sh*t pedal", was out of ajustment. Lucked out-----so far !

 

[overworked]

dirt farmer, yes it is possible and does happen alot for trans oil to overfill pump drive ( gear case ). as for not moving there is a reset in the hystat that if you drop below a set pressure at the charge pump the hystat won't try to move untill u put lever back forward to stop, drain filter housing then remove filter and inspect for metal, brass or white and green plastic. get a guage and check charge pump pressure, let me know i can send u info on taking pressures. (easy). steel lines under top cover present most probles with packings in nuts, line to underspeed valve leaks, looses pressure and underspeed valve dosent rise and machine will not move, i have worked on many 963 and 973.

 

[overworked]

and yes tracks should slow as u work bucket/boom hard, it so engine rpms stay up and u have full power to hyd pumps, if u get into big pile and try to lift/curl and the tracks spin then u are out of adjustment and u are loosing hyd pressure to bucket and boom.

 

[Jon S]

I just adjusted the linkage a little. It seemed to fix the problem. Sorry for the delay in answering.