# John Deere 450G Farm Dozer Clutch Problem



## bcavender (Jun 23, 2018)

I have a 1994 450G (793 991) Direct Drive dozer we use for general work around the farm for roads/drainage/etc. Engine/tracks are in good shape (5600hrs), but I have a transmission problem. The previous owner I purchased it from about four years ago told me he had the transmission "rebuilt" a couple years before I purchased it. His dealer confirmed the work. I didn't figure that I would see transmission problems for a good while since its use here is pretty low, but that was not our luck.

Transmission input supply pressure is 175-185psi. Forward clutch port pressure was 175, but the pressure on the reverse port falls off to 135psi when engaged. It will go forward, but not in reverse. Control linkages appear tight and functional. It seems that reverse clutch plates are likely cooked. I did find a few chunks in the suction screen that look like plate chips. I am 3-4 hours from the nearest Deere construction equip service center. Costs here are likely pretty significant between here and there.

*Has anyone here gone through the process of pulling the 450G direct drive transmission out the backdoor and replacing the clutch plates?* 

If so, what was your experience? Any big buck special tools required? Any complications that make it too big of a tech/time headache to DIY and it's better to have a dealer do the rebuild? _*Is this model prone to eating clutches? *Any suggestions about something I missed?_

I did find one video that showed some basics of the transmission install process that shows it sure isn't trivial, but probably not impossible with a bit of farm boy leverage and perseverance:






Any and all comments/guidance welcome!!!
Bruce


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## RC Wells (Dec 26, 2008)

The 450G is a very good crawler, but you do not want to run it with a sustained load in one direction or the other for a long period or it overheats the hydraulic fluid in the transmission and will cook the clutches and make them brittle. You also do not want to work it at all at partial throttle or it chews the clutches into pulp. And, never go from forward to reverse on the go, always come to a full stop when changing direction.
If you have the repair manual and a movable cherry picker, the transmission assembly is quite easy to pull and repair. It requires no tools beyond the usual complement found in most farm shops, and the manual lists all the required tools. I would not attempt removal without the manual, as it is quite prescriptive.
Where it gets a bit problematic is cleaning the internal transmission hydraulic system of the treated paper friction material. That hurdle does not usually occur if the screen and filter are sound, but if the pressure pistons do not move with air pressure, then I recommend just exchanging the unit for a rebuilt and swapping. Pay careful attention to the O rings on the hydraulic coupler, if one falls off one of the control lines the entire unit has to be pulled and O ring replaced.
You do want to do the hydraulic pressure tests outlined in the manual, as most often it is a control failure up stream of the transmission that leads to a clutch pack failing to engage (if the transmission has not been abused). Your problem may well be much simpler and easier to fix than you now believe.


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## bcavender (Jun 23, 2018)

RC,
Thank you for the good info! I sure would like to find a control system failure, but my luck doesn't seem running that way it appears.

Your point about not running the machine in a single direction for a long time is interesting on the overheat angle. 99% of my work has been short back and forth moves with no long runs. I always stopped before reversing, so that probably didn't enter into this. However, *I almost never ran the unit and full throttle.* That chewing clutches is a real head scratcher as the forces should be lower and would seem like a design flaw by Deere. Are you thinking, it is a result of lower clutch pressure at lower rpms and that allows slippage and plate damage?

I just got the TM1404 manual which is good on the transmission removal, but unfortunately it refers to the TM1403 manual for the steering clutch pressure measuring procedure _:^( _Those manuals are not cheap. Will look that up.

I had the suction screen off about 25 hr ago when I experienced a transmission low supply pressure alert. The screen was badly clogged, but intact and in good shape.










Cleaning that cleared the pressure alarm, but all the junk on the screen left me with a foreboding of trouble to come even though the machine operated fine. I was hoping that when the prior owner had Deere rebuild the transmission, the mechanic had failed to clean the screen. Now I am guessing this detritus is clutch material from the last rebuild.

You mention a "paper" friction material. ??? That sounds almost incredible that a machine as heavy as this would use a material like that deep inside a 584 lb transmission built like a brick outhouse.


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## bcavender (Jun 23, 2018)

Can you pass along more insight?

I would really like to know if this transmission is prone to repeated problems so I can make some sensible decisions about how I need to go forward. The rebuilt unit won't be cheap and I can't afford to burn up another one as a learning curve.

Thanks!

Bruce


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## DGargus (Nov 21, 2021)

I’ve got the exact same issue with the same tractor. What did the issue end up being and what did you do to fix the issue?


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