Cat D6R Jerking into reverse? Newbie question

[BushWackerFarmer]

I'm looking for a farm dozer to clear some land. I looked at a 1997 D6R LGP today. I have a 210 Hyundai excavator so I know a bit about checking tracks and these ones are pretty good. Good enough for the 500 hours I'll need this machine for. It has fingertip controls and those seem to disengage and engage pretty smoothly. The problem is when you step on the decellerator and click it into reverse it sits there and as you let off the decellerator it sometimes gives a jerk into motion. Doesn't seem to do it going forward just starts creeping then moves nicely as you let off the pedal. It was about 0C (32F) today. I had it running about 15 minutes. The engine was slowly coming up to temp, the transmission would have been pretty cold. I think it could be 4 scenarios:
A: That's normal.
B: It's doing it because it's cold.
C: It needs calibration.
D: Run like hell from this machine.

Any thoughts?

 

[Nige]

Get all the systems up to normal operating temperature. You can do that by stalling it against the brakes. Does it still do it.?

Take a look at the transmission oil. Is it clear & bright or dark & cloudy.? Does it smell burned.?

It may need a clutch modulation valve calibration.

How many total hours on the machine.?
Transmission & pump original.?

 

[BushWackerFarmer]

Get all the systems up to normal operating temperature. You can do that by stalling it against the brakes. Does it still do it.?

Take a look at the transmission oil. Is it clear & bright or dark & cloudy.? Does it smell burned.?

It may need a clutch modulation valve calibration.

It's 4 hours away now. Was quite a drive today. Transmission oil looked new.

 

[Nige]

Total hours.?
Transmission, converter, & transmission pump original.?

 

[BushWackerFarmer]

14k hours. I don't know what if anything has been changed.

 

[Rustyshacklford]

First off I’m no mechanic, but if I recall I was running a couple 6R’s that were shifting very hard almost jumping even w the decel all the way down. The mechanic swapped out what I think was some kind of solenoid just above the transmission looking from the rear. Maybe nige knows what I’m talking about and can expit better.

 

[Nige]

14k hours. I don't know what if anything has been changed.

If they are original the powertrain components won't have a huge amount of life left in them. I suppose it all depends how many hours you plan on putting on it. Did I read it right in your OP - 500 hours.?
Some type of project I assume.?

I would need a Serial Number to check but IIRC there is an accumulator in the powertrain oil system whose sole purpose is to aid in smoother shifting. If the tractor you looked at has one and it is discharged that could potentially be the issue.

 

[Nige]

The OP supplied me a Serial Number and there is no accumulator in the powertrain oil system on that particular model, so that rules that out.

It's hard to suggest this because the OP has not bought the tractor yet, but draining the transmission oil and removing/inspecting the magnetic screen located in the transmission pump suction line might be revealing. The other option would be to take a sample of the powertrain oil and have it analyzed by the Cat dealer, especially for contaminants (a sign of clutch wear). It might probably cost CAD$50 @ Toromont.

I still think a re-calibration of the transmission clutch modulating valves should be the first planned step if the OP was to buy it.

 

[BushWackerFarmer]

Well I got 'er bought so I'll keep this updated. Talked to Finning Cat and the service orders were for jumping into park randomly. First call they swapped out the park switch in the seat. Second call a month later changed out the priority valve spool. Seems to have worked fine since then. No transmission oil change or calibration charges on either call. Last calibration service call was at least 15 years ago. Wish me luck.

 

[tctractors]

No Accumulator on the R Series but there is a priority valve under your left foot as sat in the Cab, to get to it you need to drop the Belly Plate is best then connect 2 pressure gauges (0-600 psi) on the test ports, at speeds bellow 1350 (I think?) you will see the mag coil re-direct oil into the trans to help with the low speed shift, the Accumulators that are fitted on the T series carry out this task.

 

[BushWackerFarmer]

Well I have the machine home and replaced about 100 loose track pad bolts. When it's warm it doesn't jump into gear. Everything is very smooth. I used it to push some trees for half an hour twice and everything was great. Just took it to the real bush today and it says the transmission is overheating. I walked it a mile in 3rd gear full throttle and it was fine. After I made the first pass through the bush the transmission temp got close to the red and the trans light and brake light came on. Active codes are 30 96F03 (fuel sending unit is disconnected at the tank) and 30 271F05. Also getting 30 819F02 and 30 821F04. Display data link erratic and display power supply short to ground. There's a bunch of inactive 113 codes that may be related to the previous park brake problems. Need to erase those and see what comes back. Could this be loose wires under the dash?

The transmission oil is at the full mark and clean/bright. Touching the dipstick doesn't seem that hot. The bottom of the big circle on the transmission is pretty warm as is the lower right and left corner sides of the transmission. You can keep your bare hand on them but it feels pretty warm. How warm does the transmission run normally? Is it just erratic monitor system? Hate to drive it with gauges running high.

Where is the service click box connector on this machine? Operators manual says it should be behind the seat but there is nothing back there. There is a connector on the engine side of the firewall. Is that it?

 

[Nige]

Where is the service click box connector on this machine?

On the floor behind/under the seat. The photos show the location with the seat removed which is not very helpful.



Regarding your transmission temps an infra red heat gun is your friend. Point & shoot, record some actual temperatures.

 

[BushWackerFarmer]

Ok, I've got a Fluke infrared temp gun. I'll try to find the hottest spot and record it.

 

[Nige]

Ok, I've got a Fluke infrared temp gun. I'll try to find the hottest spot and record it.

Shoot temps everywhere. Torque converter outlet, transmission cooler inlet/outlet, transmission case, pump, etc, etc. While you're at it shoot the temps of the radiaotr inlet/outlet hoses.

Also take a good look at the radiator. Have someone outside looking and shine a light from the inside of the engine compartment. Move the light everywhere, especially in the corners. That will give you a good idea of what % of the core is plugged.

 

[BushWackerFarmer]

Worked it hard as I could pushing trees for 30 minutes. Hottest spot I could find was at the rear bottom part of the transmission. 164 F. Gauge behaved and only got to the halfway mark. I think I have wiring issues in the dash. This machine has a heater core under the hood and a fan added on in the dash right behind the monitor box. The monitor module is protruding a couple inches out of the dash to make room for the fan I guess. I'll have to investigate if that is pinching wires.

Found the service connectors. Not behind the seat. Under the dash facing straight down on the left side.

 

[BushWackerFarmer]

Maybe the monitor module is getting too hot? It was about 20F today and with the fan on low it was cooking me out of the cab in a T-shirt. I could run the heater taps on the block half closed maybe.

 

[Nige]

Regarding the jerky engagement of the transmission. If you can get your ET to connect try running a calibration of all five transmission clutch modulation valves.

 

[BushWackerFarmer]

Now that I'm running it nice and hot it's shifting very smoothly. The fingertip controls with clutch and brake are really smooth. I don't think it needs calibration not that it wouldn't hurt to do it again as according to the service records it's been a long while.

 

[tctractors]

the hard shifting from forward to reverse will point to a fault with the forward modulation valve it will be hanging on incorrectly, your transmission would benefit from having the latest flash file installed I think it was from 2010, with a full clutch fill calibration, also check the foot brake position values, if you try to calibrate the transmission with a click box its common to find a modulation valve will not lift to the correct pressure value even if you fit a new CAT valve so best of luck, as you state it runs well when hot it would be telling me it needs all of the above.

 

[Nige]

Good point on the Click Box Tony. Nothing more than old school technology required to calibrate this old girl, even though ET maybe does it a bit easier. See Pages 1-7 of the attachment. Mode 6, submodes 31-35 & 40 are the relevant ones.

For more information click on the link for the Click Box thread.