753 C steering to right

[BobcatBob]

Just bought a 753C with a known issue of slightly steering to right. The problem corrects itself when right stick is fully exteneded forward, though the machine labors as if under significant load. Any ideas where to start? Newbie

 

[Fishfiles]

Forgetting about the laboring to start with , the steering can be adjusted to make it track straight with an adjustment of the four flat steering bars that are held together with two bolts thru each set right in the middle of the machine , it is good to mark the bars where they are now before moving them to give a reference point , loose the two bolts and slide the bars a little to compensate for the drift ---you can jack and block the machine off the ground , raise the cab , spray paint lines on the two front tires and be able to spin the tires and see if they are in sinc with each other -------------the laboring issue could be another ball game , while it jacked up I'd check wheel bearings and the oil in the chain case to start

 

[BobcatBob]

Forgetting about the laboring to start with , the steering can be adjusted to make it track straight with an adjustment of the four flat steering bars that are held together with two bolts thru each set right in the middle of the machine , it is good to mark the bars where they are now before moving them to give a reference point , loose the two bolts and slide the bars a little to compensate for the drift ---you can jack and block the machine off the ground , raise the cab , spray paint lines on the two front tires and be able to spin the tires and see if they are in sinc with each other -------------the laboring issue could be another ball game , while it jacked up I'd check wheel bearings and the oil in the chain case to start

Thank you. I'll adjust the linkage and "pray" that works.

 

[BobcatBob]

Thank you. I'll adjust the linkage and "pray" that works.

Unfortunately, same damn problem. Linkage was not the issue. I think it's a control valve issue. Symptom's: Steers to the right after about 10 min's of use. Works fine in reverse. Pushing right stick HARD forward will engage right wheels about 25% of time (the 4th time is the charm)....machine jumps a bit, then with both sticks forward, machine starts turning to the right. When right does engage , the hydraulic's makes a quick"grunting" noise as if it is someone kind of surge (i.e. a lot of hydraulic fluid release, then normal). I brought the machine to the local dealer for a tune up, resolution on this issue.....they stated the hydraulic lines were good, no hydraulic/hydrostatic issues (lots of $$$$ for this "tune up"). Problem remains (and a line let go after 10 minutes of use....solved at a local hose shop for cheap) Any help would be appreciated (as I'm not sure I could financially handle another trip to the dealer). Thank you

 

[Tazza]

Unfortunately, same damn problem. Linkage was not the issue. I think it's a control valve issue. Symptom's: Steers to the right after about 10 min's of use. Works fine in reverse. Pushing right stick HARD forward will engage right wheels about 25% of time (the 4th time is the charm)....machine jumps a bit, then with both sticks forward, machine starts turning to the right. When right does engage , the hydraulic's makes a quick"grunting" noise as if it is someone kind of surge (i.e. a lot of hydraulic fluid release, then normal). I brought the machine to the local dealer for a tune up, resolution on this issue.....they stated the hydraulic lines were good, no hydraulic/hydrostatic issues (lots of $$$$ for this "tune up"). Problem remains (and a line let go after 10 minutes of use....solved at a local hose shop for cheap) Any help would be appreciated (as I'm not sure I could financially handle another trip to the dealer). Thank you

What did the dealer do to 'resolve' the issue?
It almost sounds like the levers that attach to the pump is loose. They are alloy and can wollow out if they get loose. It would make the hydraulics jumpy. They have a square section milled into them to hold on the arms that come out of the pump its self.

 

[BobcatBob]

What did the dealer do to 'resolve' the issue?
It almost sounds like the levers that attach to the pump is loose. They are alloy and can wollow out if they get loose. It would make the hydraulics jumpy. They have a square section milled into them to hold on the arms that come out of the pump its self.

WHen I spoke with the repair shop manager, we reviewed all items serviced (engine mounts, cab shocks, harness bar safety tabs (plastic had rotten out), fluids,tires, etc......and steering issue to right). He stated the linkage was fine and when they tested the machine, no steering to the right was found (not sure how long he ran the machine, but it does act up after about 10 minutes). I'm nervous as this doesn't appear to be a hydraulic motor issue (works fine in reverse). Possibly a worn spool? No fluids are leaking anywhere (knock on wood). Machine's about 15 years old.....wondering if there are any worn o-rings......fluid might be getting by inside the control unit (as it does surge, moving forward straight for a brief moment, then continues to turn to the right). I have not worked on hydraulics (since taking a '78 nova transmission apart to replace the clutch about 20 years ago....STEEP learning curve). Any ideas would be of great help. Thank you

 

[Tazza]

WHen I spoke with the repair shop manager, we reviewed all items serviced (engine mounts, cab shocks, harness bar safety tabs (plastic had rotten out), fluids,tires, etc......and steering issue to right). He stated the linkage was fine and when they tested the machine, no steering to the right was found (not sure how long he ran the machine, but it does act up after about 10 minutes). I'm nervous as this doesn't appear to be a hydraulic motor issue (works fine in reverse). Possibly a worn spool? No fluids are leaking anywhere (knock on wood). Machine's about 15 years old.....wondering if there are any worn o-rings......fluid might be getting by inside the control unit (as it does surge, moving forward straight for a brief moment, then continues to turn to the right). I have not worked on hydraulics (since taking a '78 nova transmission apart to replace the clutch about 20 years ago....STEEP learning curve). Any ideas would be of great help. Thank you

It doesn't use a spool for the drive. Its done with a vairable displacement piston pump, one for each side mounted inline. The more you move the stick back or forth the more or less fluid is pumped my the piston pump. As it runs fine in reverse i'd doubt the motor is an issue either. I guess it could be a high pressure relief in the pump... They have allen head sockets on them, they simply screw out. I am not sure if the one you need to look at is on the top or bottom of the pump though. If you download one of the manuals for a 753 or 751 have a look at the pump. It will show high pressure relief valves, 5000 PSI i guess one of them could be acting up causing your issue, but only after 10 minutes of operation seems odd.
There really isn't a whole lot to the drive system, pump, motor levers. Only one direction does seem to point to the relief or possible the shuttle valve in the drive motor... There will be an allen head plug, this is your shuttle valve. Its only a guess it could be sticky.

 

[BobcatBob]

It doesn't use a spool for the drive. Its done with a vairable displacement piston pump, one for each side mounted inline. The more you move the stick back or forth the more or less fluid is pumped my the piston pump. As it runs fine in reverse i'd doubt the motor is an issue either. I guess it could be a high pressure relief in the pump... They have allen head sockets on them, they simply screw out. I am not sure if the one you need to look at is on the top or bottom of the pump though. If you download one of the manuals for a 753 or 751 have a look at the pump. It will show high pressure relief valves, 5000 PSI i guess one of them could be acting up causing your issue, but only after 10 minutes of operation seems odd.
There really isn't a whole lot to the drive system, pump, motor levers. Only one direction does seem to point to the relief or possible the shuttle valve in the drive motor... There will be an allen head plug, this is your shuttle valve. Its only a guess it could be sticky.

I just opened the manual and looked at the schematic. We'll give it a try and see if that provides a direction as to the cause. Unfortunately, it's sitting in our yard with an air/fuel problem....troubleshooting. Thank you for the support. I'll report back as soon as we get er going again.

 

[Bobcat Trouble Shooter]

I just opened the manual and looked at the schematic. We'll give it a try and see if that provides a direction as to the cause. Unfortunately, it's sitting in our yard with an air/fuel problem....troubleshooting. Thank you for the support. I'll report back as soon as we get er going again.

working on a customers 753C with the same trouble. Shudders like crazy once it warms up and you push the right lever forward. Reverse works fine. Full fluid and filter change including the case return filters. Some crud in the right case return filter but not that bad. Replaced both high pressure (5000psi) Replenishing valves on the bottom of the pump and the problem persists (pump does not have to be removed for this like the book recommends). At this point thinking it may be the right drive motor shuttle valve or possibly a small air leak causing cavitation within the drive motor (unlikely because reverse is fine though). Bobcat techs I know have no suggestions after replacing HP Replenishing valves. We'll see...

 

[Tazza]

working on a customers 753C with the same trouble. Shudders like crazy once it warms up and you push the right lever forward. Reverse works fine. Full fluid and filter change including the case return filters. Some crud in the right case return filter but not that bad. Replaced both high pressure (5000psi) Replenishing valves on the bottom of the pump and the problem persists (pump does not have to be removed for this like the book recommends). At this point thinking it may be the right drive motor shuttle valve or possibly a small air leak causing cavitation within the drive motor (unlikely because reverse is fine though). Bobcat techs I know have no suggestions after replacing HP Replenishing valves. We'll see...

If you suspect a shuttle valve, its not a bad idea to try swapping motors over, see if the issue moves.

 

[Bobcat Trouble Shooter]

If you suspect a shuttle valve, its not a bad idea to try swapping motors over, see if the issue moves.

Finally found the problem. It was not the shuttle valve. It was an internal crack in the drive motor housing. Had to look very carefully as it was hidden under a sealing ring. Looks to me to be a design/casting flaw as the casting is very thin at that location. As the machine warmed up the crack would open and and the condition would worsen. Best part is that Bobcat has a superceeded replacement drive motor with a completely different housing. I wonder why. They may be aware of a casting problem. Hope this helps someone else.

 

[Tazza]

Finally found the problem. It was not the shuttle valve. It was an internal crack in the drive motor housing. Had to look very carefully as it was hidden under a sealing ring. Looks to me to be a design/casting flaw as the casting is very thin at that location. As the machine warmed up the crack would open and and the condition would worsen. Best part is that Bobcat has a superceeded replacement drive motor with a completely different housing. I wonder why. They may be aware of a casting problem. Hope this helps someone else.

Glad you found the problem, not so good that it was no doubt an expensive fix.

 

[Skidder Dave]

Glad you found the problem, not so good that it was no doubt an expensive fix.

Darn - I realize this is a very old (2011) post thread, but I am having almost exactly the same problem with my 753H that I call "Bob". I was hopeful that changing out both Relief/Replenishing Valves (Item 5 on the hydraulic schematic) might solve this. Haven't tried it yet. But this post discussion is not encouraging. I will post whatever I try and the outcome. (Yes, I have tried adjusting the linkage). My problem sounds identical, except it occurs right after startup - no warmup required. Bob is still functional enough to use, but fighting the steering gets very old after while. If anyone out there in the forum thinks changing out the Relief / Replenishing Valve IS (or IS NOT) a viable solution worth trying, please advise your thoughts. Special thanks to SSF - I appreciate the helpful advice received here, and I donated $$$ today in appreciation. You help to keep my dinosaur running!

 

[Skidder Dave]

Darn - I realize this is a very old (2011) post thread, but I am having almost exactly the same problem with my 753H that I call "Bob". I was hopeful that changing out both Relief/Replenishing Valves (Item 5 on the hydraulic schematic) might solve this. Haven't tried it yet. But this post discussion is not encouraging. I will post whatever I try and the outcome. (Yes, I have tried adjusting the linkage). My problem sounds identical, except it occurs right after startup - no warmup required. Bob is still functional enough to use, but fighting the steering gets very old after while. If anyone out there in the forum thinks changing out the Relief / Replenishing Valve IS (or IS NOT) a viable solution worth trying, please advise your thoughts. Special thanks to SSF - I appreciate the helpful advice received here, and I donated $$$ today in appreciation. You help to keep my dinosaur running!

And again, an earlier post said probably not the drive motor, cause it worked fine in reverse. Same as my situation. BUT it ultimately WAS the drive motor. Hmmm... WTH???

 

[Tazza]

And again, an earlier post said probably not the drive motor, cause it worked fine in reverse. Same as my situation. BUT it ultimately WAS the drive motor. Hmmm... WTH???

There are seals in teh drive motors that can fail, it can cause high pressure to by-pass giving power in one direction only. The best place to start is always the motors, they are the easiest to access and open up to look at.

 

[Skidtech]

Darn - I realize this is a very old (2011) post thread, but I am having almost exactly the same problem with my 753H that I call "Bob". I was hopeful that changing out both Relief/Replenishing Valves (Item 5 on the hydraulic schematic) might solve this. Haven't tried it yet. But this post discussion is not encouraging. I will post whatever I try and the outcome. (Yes, I have tried adjusting the linkage). My problem sounds identical, except it occurs right after startup - no warmup required. Bob is still functional enough to use, but fighting the steering gets very old after while. If anyone out there in the forum thinks changing out the Relief / Replenishing Valve IS (or IS NOT) a viable solution worth trying, please advise your thoughts. Special thanks to SSF - I appreciate the helpful advice received here, and I donated $$$ today in appreciation. You help to keep my dinosaur running!

I have repaired three different 753’s with the same issue. All three steere to the right. All three had a small crack in the volute section of the right drive motor. The motors had to be disassembled to find the crack. I have never seen this problem on the left. I am guessing this is why Bobcat only sells a retrofit kit which utilizes a larger drive motor with a thicker casting. Inspect the case carefully. Rubbing alcohol sprayed on the casting will draw attention to any cracking.

 

[Tazza]

I have repaired three different 753’s with the same issue. All three steere to the right. All three had a small crack in the volute section of the right drive motor. The motors had to be disassembled to find the crack. I have never seen this problem on the left. I am guessing this is why Bobcat only sells a retrofit kit which utilizes a larger drive motor with a thicker casting. Inspect the case carefully. Rubbing alcohol sprayed on the casting will draw attention to any cracking.

Interesting, something to keep an eye out for.
I wonder if it's due to most of the hard work is done in forward, so that side of the motor may have a slight flaw allowing it to fail over time, as the left side rotates the opposite way under most of the load, the issue does not surface.

 

[Skidder Dave]

Darn - I realize this is a very old (2011) post thread, but I am having almost exactly the same problem with my 753H that I call "Bob". I was hopeful that changing out both Relief/Replenishing Valves (Item 5 on the hydraulic schematic) might solve this. Haven't tried it yet. But this post discussion is not encouraging. I will post whatever I try and the outcome. (Yes, I have tried adjusting the linkage). My problem sounds identical, except it occurs right after startup - no warmup required. Bob is still functional enough to use, but fighting the steering gets very old after while. If anyone out there in the forum thinks changing out the Relief / Replenishing Valve IS (or IS NOT) a viable solution worth trying, please advise your thoughts. Special thanks to SSF - I appreciate the helpful advice received here, and I donated $$$ today in appreciation. You help to keep my dinosaur running!

To all 753H owners with “steers to the right / ok in reverse” issues - after years of tolerating the problem, the RH drive on “Bob” finally crapped out completely in forward. I could only do donuts to the right in forward, but reverse was fine. So I backed my way back to the barn. Researched a new (upgraded) Bobcat final drive - $2600-ish - UGH! Researched rebuilt and used motors $500 to $800-ish, IF you can find one. UGH! Finally ended up watching maybe 3 or 4 YouTube videos on how to do a seal kit rebuild on the drive. Bought the kit for $220-ish. Took a couple hours to rebuild - shoulda been a half hour job but I was ultra careful. Found a couple disintegrated internal orings. Worst part was the reinstall. Do yourself a favor - a make a couple 1/2-13 x 5 inch long dowels to thread into the chain case motor mount to easily guide the motor into place. Buy extra flat face fitting orings in advance - you WILL bugger up one or two. Also pre-align the motor male spline shaft prior to pushing the motor into place. It’s really not a difficult job, but I was sweating bullets. “Bob” drives GREAT now - in a straight line too! Success! Woohoo!

 

[Tazza]

To all 753H owners with “steers to the right / ok in reverse” issues - after years of tolerating the problem, the RH drive on “Bob” finally crapped out completely in forward. I could only do donuts to the right in forward, but reverse was fine. So I backed my way back to the barn. Researched a new (upgraded) Bobcat final drive - $2600-ish - UGH! Researched rebuilt and used motors $500 to $800-ish, IF you can find one. UGH! Finally ended up watching maybe 3 or 4 YouTube videos on how to do a seal kit rebuild on the drive. Bought the kit for $220-ish. Took a couple hours to rebuild - shoulda been a half hour job but I was ultra careful. Found a couple disintegrated internal orings. Worst part was the reinstall. Do yourself a favor - a make a couple 1/2-13 x 5 inch long dowels to thread into the chain case motor mount to easily guide the motor into place. Buy extra flat face fitting orings in advance - you WILL bugger up one or two. Also pre-align the motor male spline shaft prior to pushing the motor into place. It’s really not a difficult job, but I was sweating bullets. “Bob” drives GREAT now - in a straight line too! Success! Woohoo!

Seals can and do go bad, i have a 753 that had no power on ons side, after cracking it open, the orings were like powder.
At least now you know what to do if/when the other side goes. If one went bad, there isa a good chance the other will not be too far behind.