Hydraulic Drive Motor....Backwards?

[Jeffscarstrucks]

I removed the track drive motor from my machine to replace the output shaft bearings. I seperated the two motor segments from the output segment and did not disturb a thing on the motor sections. The bearing replacement went fine along with a new seal and O-rings and the motor went back together fine. Today was the big install (part of a bigger undercarriage rebuild) and the lovely thing ran backwards!(opposite of control input). It is a Danfoss 400 motor that runs the track drive. I have posted this here because I know that nearly all of the folks on this forum read this section and have helped me with Bobcat isues before. I have only guessed at possible problems and the hoses are on as before. It never fails that it would happen on a Friday evening! Thanks in advance, Jeff

 

[sterlclan]

the drives on mine are timed with a valve plate inside the motor perhaps when you reassembled yours you moved the plate?worst case disassemble motor retime and put it together...or switch the hoses around.Good luck... Jeff

 

[Jeffscarstrucks]

the drives on mine are timed with a valve plate inside the motor perhaps when you reassembled yours you moved the plate?worst case disassemble motor retime and put it together...or switch the hoses around.Good luck... Jeff

Thanks, I have run it over in my mind and I don't think I moved anything. I am sure that I will end up taking it apart again. I should just change the hoses but I won't as I would ratherknow what I screwed up...lesson for next time I guess. Thanks Again, JEFF

 

[Fishfiles]

Thanks, I have run it over in my mind and I don't think I moved anything. I am sure that I will end up taking it apart again. I should just change the hoses but I won't as I would ratherknow what I screwed up...lesson for next time I guess. Thanks Again, JEFF

look to the easiest things first , could you have possibilly put the hoses on backwards when reassembling , I 'd check hose routing first ------I done quite afew bobcat drive motors and never seen that one , I have seen it happen with gear driven motors like commercial sheering where indexing or seal placement will change the direction --- I'd swop the hoses -- freakieeeeeee

 

[Tazza]

look to the easiest things first , could you have possibilly put the hoses on backwards when reassembling , I 'd check hose routing first ------I done quite afew bobcat drive motors and never seen that one , I have seen it happen with gear driven motors like commercial sheering where indexing or seal placement will change the direction --- I'd swop the hoses -- freakieeeeeee

Its probably timing, you only need to be out one hole for it to run backwards.

 

[skidboy]

Its probably timing, you only need to be out one hole for it to run backwards.

Is this a Bobcat ? If so what model

 

[Jeffscarstrucks]

Is this a Bobcat ? If so what model

Tazza, I think that you are dead on...I took the motor back off today and disassembled completely. I am sure that when I lined up the inside shaft that it must have moved now that I see the big picture. It is always better to learn the hard way as you NEVER forget! Now I am not sure how to time it other than trial and error...a 50-50 chance.. Thanks guys and I will let you know how it goes, JEFF

 

[Tazza]

Tazza, I think that you are dead on...I took the motor back off today and disassembled completely. I am sure that when I lined up the inside shaft that it must have moved now that I see the big picture. It is always better to learn the hard way as you NEVER forget! Now I am not sure how to time it other than trial and error...a 50-50 chance.. Thanks guys and I will let you know how it goes, JEFF

Skidboy - the earlier machines had motors that needed timing, my 731 and 743 both need timing if you open them up. There is a valve plate that needs to line up at the back to direct the flow in the rite sequence. They ran eaton bearing-less motors if thats any help.

 

[skidboy]

Skidboy - the earlier machines had motors that needed timing, my 731 and 743 both need timing if you open them up. There is a valve plate that needs to line up at the back to direct the flow in the rite sequence. They ran eaton bearing-less motors if thats any help.

There is a lot of knowledge on this forum,but it seems to me that an awful lot of time is wasted by people not telling us the make and model of the machine that they magically want others to diagnose ! my 2c worth

 

[Tazza]

There is a lot of knowledge on this forum,but it seems to me that an awful lot of time is wasted by people not telling us the make and model of the machine that they magically want others to diagnose ! my 2c worth

I do agree, its much better for people to give a model and year if known for all questions.... I wonder if we should setup guide lines for posts? but most people do whatever they want around here, posts in the wrong sections etc but its all easy to fix.
I'd just rather it not be like other forums i have been on, they are really strict with guide lines like that. Around here we are pretty easy going.
I may start a thread in suggestions

 

[73Eldo]

I do agree, its much better for people to give a model and year if known for all questions.... I wonder if we should setup guide lines for posts? but most people do whatever they want around here, posts in the wrong sections etc but its all easy to fix.
I'd just rather it not be like other forums i have been on, they are really strict with guide lines like that. Around here we are pretty easy going.
I may start a thread in suggestions

In his first post he implied that this issue was not on a bobcat and he posted in this section because more people read and respond here vs. the other sections. It does seem to be true, look at the number of unanswered posts in the other sections, even when they seem to be basic engine and hydraulic questions.

 

[Tazza]

In his first post he implied that this issue was not on a bobcat and he posted in this section because more people read and respond here vs. the other sections. It does seem to be true, look at the number of unanswered posts in the other sections, even when they seem to be basic engine and hydraulic questions.

Maybe, but i personally look all the way down for new posts. The reason the other brands don't get as much attention as they aren't as popular so there aren't as many people with experience that can offer advise. Like they have a pump problem, i have never opened a pump that wasn't off a bobcat so i really can't comment. Same with the engines, all diesels are essentially the same but there will be differences, you don't want to give advise that may be wrong or cause more problems than there were before. Well thats just me.

 

[Jeffscarstrucks]

Maybe, but i personally look all the way down for new posts. The reason the other brands don't get as much attention as they aren't as popular so there aren't as many people with experience that can offer advise. Like they have a pump problem, i have never opened a pump that wasn't off a bobcat so i really can't comment. Same with the engines, all diesels are essentially the same but there will be differences, you don't want to give advise that may be wrong or cause more problems than there were before. Well thats just me.

I agree that it is important to have specific info on any machine and the ASV MD 70 that I am working on now is no different. I asked this generic hydraulic question because a motor doesn't really know what color paint it is pushing around. I know that most readers and contributors are Bobcat owners as I have been and will be. The majority of the expertise is here and that is what I was hoping to tap into as an every day reader. I really didn't mean to offend and thanks to all. I will let you know how it goes as I just reassembled the motor for the machine and will try it again as soon as I get a chance. Thanks again, Jeff

 

[Tazza]

I agree that it is important to have specific info on any machine and the ASV MD 70 that I am working on now is no different. I asked this generic hydraulic question because a motor doesn't really know what color paint it is pushing around. I know that most readers and contributors are Bobcat owners as I have been and will be. The majority of the expertise is here and that is what I was hoping to tap into as an every day reader. I really didn't mean to offend and thanks to all. I will let you know how it goes as I just reassembled the motor for the machine and will try it again as soon as I get a chance. Thanks again, Jeff

That is true, but the biggest problem is some parts are made specifically for bobcat like my 751 and 753 drive motors are made by eaton for bobcat. Most of the parts are generic and i agree paint colour means nothing.

 

[Jeffscarstrucks]

That is true, but the biggest problem is some parts are made specifically for bobcat like my 751 and 753 drive motors are made by eaton for bobcat. Most of the parts are generic and i agree paint colour means nothing.

It is always an adventure learning all of different intricate mechanicals when working on all kinds of machines. Taz, Do you think that one could retime the motor by moving the center plate in the input (fluid) section by going through the 'A' port with a tool and moving the plate about two thirds of the way between two feed holes on the plate? (is that clear....). I am assuming that if it runs backwards that this would be the fix, To redirect fluid flow per given input. I am trying to figure this out on the fly as I don't seem to find anything on the net. It seems that this Danfoss motor uses an Eaton final drive (similar to Case) with two tapered bearings that oppose each other like car wheel bearings. Thanks, JEFF

 

[Tazza]

It is always an adventure learning all of different intricate mechanicals when working on all kinds of machines. Taz, Do you think that one could retime the motor by moving the center plate in the input (fluid) section by going through the 'A' port with a tool and moving the plate about two thirds of the way between two feed holes on the plate? (is that clear....). I am assuming that if it runs backwards that this would be the fix, To redirect fluid flow per given input. I am trying to figure this out on the fly as I don't seem to find anything on the net. It seems that this Danfoss motor uses an Eaton final drive (similar to Case) with two tapered bearings that oppose each other like car wheel bearings. Thanks, JEFF

You could try that, i'm not 100% sure how the timing actually works as i haven't had to pull a motor with a valve plate that needs timing, the ones i have done were all set with a dowel. I thought i had details online but don't seem to.
I can't see a problem if you move the plate a bit of a turn to work out where it should be.

 

[sterlclan]

You could try that, i'm not 100% sure how the timing actually works as i haven't had to pull a motor with a valve plate that needs timing, the ones i have done were all set with a dowel. I thought i had details online but don't seem to.
I can't see a problem if you move the plate a bit of a turn to work out where it should be.

the plate on the drives I have are splined onto the shaft......one tooth either way will reverse direction I have a pdf for assembly I can email it if you like let me know.....Jeff

 

[Jeffscarstrucks]

the plate on the drives I have are splined onto the shaft......one tooth either way will reverse direction I have a pdf for assembly I can email it if you like let me know.....Jeff

Sterlcan and Taz, I am happy to report that it went together and ran the right direction tonight. I wish that I could say that it was an educated move but it was really just luck. I would love to have your assembly pdf so that I can print it for my files as mine is the same design. I tried to find that info but worked from some other info on the Danfoss site. I would really appreciate it. My e-mail is [email protected] . I do not like to own things and not know how they work (common here I would guess) so thanks again for steering me right on this problem and to all who contribute here as I look forward to checking it every day. JEFF

 

[Jeffscarstrucks]

Sterlcan and Taz, I am happy to report that it went together and ran the right direction tonight. I wish that I could say that it was an educated move but it was really just luck. I would love to have your assembly pdf so that I can print it for my files as mine is the same design. I tried to find that info but worked from some other info on the Danfoss site. I would really appreciate it. My e-mail is [email protected] . I do not like to own things and not know how they work (common here I would guess) so thanks again for steering me right on this problem and to all who contribute here as I look forward to checking it every day. JEFF

Sterlcan, Got the info, exactly what I needed, Thanks, JEFF