John Deere dozer hydrostatic drive rebuild

I was curious if any of you guys have attempted to rebuild your hydro final drives on the older John Deere dozer or loaders? If so how did it go?
 
Late 70s when the first 750s came out I could rebuild one and make it work but been some time since then. Back then they did not hold up well. Don,t think I ever went into and 850 but did several 750s. Parts are not cheap and knowing what to use and what is worn is touchy.
 
I just traded for a 79 755 loader that the cab caught on fire burnt the hydraulic hoses and wires underneath. Havent messed with an hydro before been reading up on them trying to familiarize myself with the way they work. Gonna go get to tomorrow.

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The very first thing you will have to address is moving it. We always just pulled the sprocket bolts and let the sprocket spin on the hub otherwise moving it you will just have to drag it. Next right under you feet the main steering control valve, get it off and drop it in a bucket of diesel right quick. If you are lucky you pumps may be ok but that valve is the real kicker. High to replace and has to be right. I built several of the burnt ones because in the Mississippi log woods they would burn. That one dose not look too bad. IF this is something you plan on keeping and running be advised that they are absolutely the hottest thing you will ever sit in. The oil tanks are up beside you and they get too hot in the loader. Running one for anything over an hour or so it punishing
 
Yeah have a manual for it. And it says the dang breaks are engaged with no hydraulic pressure? Im getting a wrecker a big wrecker and another big winch to help drag it on a trailer. Not sure how its gonna work hoping I can drag it up. Yeah those controls seem fairly complicated. I will do that. Any other suggestions shoot them my way. The controls on the transmission control valve seem to be froze up? Has been setting for the past 3 years none of the pedals will move. What about flushing the transmission? Would you use diesel? To me that would be better but the book says a 10 weight motor oil?
 
Spinning the hydostatic drive parts is not a good idea. You need to disconnect the drive to the tracks so it does not spin the hydro parts.
 
Is there away to disconnect the drives? Are you talking about disconnecting the 2 driveshafts that feed both final drives?
 
More less the crawler is an hr away. I have a manual but its 1k pages Im sure Im missing something. But if its something I can do in an hour or so Id like to do it. Just to move the thing closer to work on it without tearing too much stuff up I dont need to tear up.
 
You would think if those Hydros were bad i would have found the weak points. i did have and issue with a charge pump on it . I ran one of he first 750 J D's in the oil patch , equipped with a W6 F Hyster winch with 1 and 1/8 blue wrap drill line over the 7/8ths that was what was suppose to be on it it built on avg. of five drilling rig locations a week five entrance ways and atleast one drilling rig move . Once i figured out how to run it i was impressed with it . I had no mercy on it . When the charge pump went she had like 250 Hrs on it and when the mechanic from the deere dealership arrived also he had 6 people from deere that flew in with the parts and also dove in with the repairs as they had to pull parts from the line . I was on a drilling location build when it went down . I had moved in the 450C to try and get the job done as i was running out of time . when done the guys from Deere went thru the set up and told me it was done go try it out , vary first blade i tryed to push she had no getty up and go . Back over to where they were standing and told them that she was a DOG and did not have what the 450 has. This one deere guy and i got into it and i asked him if he could run it nd he told me he had over 400 Hrs running a 750 . Aske him if he knew how to cut a slot trench and he said yes , i said you take the 750 and i'll run the 450 as i have two slot trenches to make 200 feet lone and 6 feet deep and we will do this for 1/2 hour and we will see who can make the bigger pile of dirt a the end of the cut . we only ran for fifteen min.or so when i ran out of fuel and my pile was twice the size . They agreed that she was NOT running right that is when old Al said here let me check and he put the gauges back on and tweaked here and a tweak there and another tweak , NOW she would throw rooster tails off the tracks and never slow down . While we were talking the one engineer asked me what i thought would be and improvement to make it better , i told him that to run it to it's max the operator needed three arms and hands , ya needed one hand on the direction control one on the steering levers and one on the blade . BUT IF you put the steering on the feet then you can steer change direction and control the blade all at the same time . I only knew two position of the direction control , all the way forward and all the way back wide open throttle . I would use my elbow to knock the blade control into float as i was changing directions while turning into a new cut and by the time the blade was going into the ground i had it lined up for the cut and back on the blade control and the travel was already all the way forward , plum loved how it would do the ground speed to torque as the load came on and then pick speed back up when the load came off and you were carrying . For dragging trucks she was smooth . while doing a Frac job i could pull two and push one , i could winch and track all at the same time . Get into a tough spot i could kick the winch into free spool while still pushing the one and once thru lock the winch and start reeling the other two in and never stop moving . When i went to help a friend start a new company i bought for them 4 750's , 4 850's 4 550's and 4 D6 D's . All the Deeres were set up by Al and he Cat's were set up / turned up by Cat . Side by side the 750's along side the D 6 D's would eat the Cat's lunch.
 
Thats good to know! Sounds like there a good piece of equipment if there all lined out and running good! I have never ran a big dozer yet. I have a 350b that I really like iv had for a few years and its a dang good little dozer and parts arent crazy expensive for them. Hoping I can get this one working again. Have 80 acres and wanting to make a road to part of my property but to do it I need a big piece of equipment to move dirt then come back with the little dozer to clean It up. And wanting to build a pond also have a ton of stumps to pull out.. Will see how it goes. I got it as a trade the guy Im getting it from says it ran good before it caught fire. Really like the rippers think I could really tear some stuff up with those. Another project to fix and toy to play with!
 
No I told you the easy way just pull the sprocket blots they will spin on the hub. Pulling the shafts to the spliter box is not going to stop but no worry about spinning the hydros because the spring brakes are going to be set
 
Ok sounds good. Thats what I am hoping for just to drag it. Thanks gonna bring tools if need be to pull the sprockets if the tracks start spinning.
 
Before you can drag it you need to release the brakes and this can be done manually , under the floor boards is a hand pump that you stick a bar in and pump off the brakes for towing . There is a section in there about moving a dead machine . I use to know this but it been a long time since the late seventys and early eighty's when i was around them . It has been i'll bet fifteen years since i was last on a dozer and it was a 750 J rental that i ran for a friend making the new free stall barn location for him . I did in four days with one dozer that five excavating companys gave bids on said it would take a week and a half with two dozers and two pans the one said , the next said his big 300 excavator and two rock trucks and a dozer and roller . we did this with the one dozer one 2255 Oliver tractor pulling the back half of and old f-600 Ford dump truck made into a trailer filled with dirt for compaction and his kid running it . When done i was with in one inch of being dead on all across a 350x 275 pad. with no laser or GPS.
 
Like i said there is a hand pump under the floor boards to pump up and this releases the brakes . had to do that with one that got swamped in a blow pit . Nothing like working in pit water elbow deep . a new Hire that said he knew how to squeeze a pit , backed out into the middle of a blow pit with water a foot over the floor plates setting ontop of drill cuttings dropped the blade and went to move . and he was STUCK and shut it off . That 750 was two weeks old . Took two 850's to drag it out . We were down one dozer and operator . Read in the operators manual on who this is done .
 
Yes just take that rim of bolts that mounts the sprocket to the carrier and the sprocket will stay right in place inside the track then it will role with the sprocket turning on the carrier. Moved several burned ones like that. Lots easier that the grease in the brakes thing.
 
You are going to need a ton of high dollar parts send me an e mail and I will give you a guy that can help .
 
I did see it in the manual but I wasnt wanting to spin the sprockets so I left it alone. Didnt wanna suck all the debris from the fire into the final drives or hurt them in anyway the tracks slid. Im sure the wrecker company didnt like it but its done now. Plus Im pretty sure everything in the cab is froze up. I couldnt move any of the foot pedals nor most of the levers, for setting 3 years it sure has a lot of frozen parts. I have my work cut out getting it running again. If it doesnt cost a small fortune.
 
Pretty much a specialty like excavator finals, not really something to tackle by most mechanics. How old of machine is it, most of the problems with our 450 deere have been with the transmission control computer that controls the hydrostat they are mounted in a way that holds moisture and corrode the circuitry
 
Its a 1978 Deere 755 pretty much everything under the seat caught fire. And is burnt to a crisp before that it supposedly was a good machine. The motor still looks good they where able to get the fire out before it burnt. I am curious what adapters I will need to hook up gauges to the pumps and drives. Definitely going to need some costly parts.But no less I will get it running again. Already invested in it. Doesnt look to have a ton of hours on it carriage still looks good so do the pins and bushings.
 
Hey do you guys know if I can bump the motor to see if it will turn over. Without hurting the transmission or drives?
 
Go and take the drive shaft out after the splitter box and you can crank the motor if you want
 
Well then it sounds like your going to need a CASE of Zep penetrating fluid . Personally been usen that stuff for going on 53 years now and i have found nothing that even comes close . Hard to find and it ain't cheap but it works . Last year the salesman called to get my yearly order and they had a promotion going if you bought one case at the promotion pice of 118 buck ya got a second case for free . I ordered two cases and got four , two went to the farm and two stayed at the house . Now i have cans EVERYWHERE . I am telling ya this stuff is almost good on toast .
 
Haha yeah Im gonna need a ton of lubricant. I ended up getting a pump up sprayer. Made my own concoction of diesel fluid,automatic transmission fluid and a gallon of pb blaster. After I power washed everything the finals dont look bad at all. Think all the caked up oil and grease might have saved them. But the hydraulic pump for the loader looks like it got pretty toasty the splitter drive shafts are shot. And a ton of hoses and cables are in need of replacing. Gonna widdle away at it. Got the shafts out. Now gonna figure out how to see if the motor will turn over. The starter got a little hot so not sure if its good or not havent gotten that far yet.
 

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