D6C how to test transmission pressure s/n 10k4334

[Milner Forestry]

I read all the threads I could find on this type dozer, and found helpful information but not exactly what I am looking for. I hope someone can please help answer some questions for me.
I have gauges and I’m handy with wrenches just need some direction.

i recently chose to purchase a cat D6c.

what it’s symptoms are:
- on start up, I put it in gear and it won’t move, but after it warms up a bit I can give it about 3/4 throttle and it will start moving. Once I get it to go that first time it does pretty good and will work without the hesitation that it has that first time after startup.

- when Pushing dirt it does pretty good in first and second gear but if I shift into third it will lose speed and seems weak in third. I always push a heavy load in first gear but my question is, is this normal to lose speed/power when shifting into 3rd under a load?

- when I push up against a big tree that won’t move, it takes almost full throttle in first gear to spin the tracks, and won’t spin the tracks at all in second or third gear, is this normal?

so those are pretty much my issues, the machine is usable the way it is but if I’m missing out on more power that I could get out of it by changing the torque converter or the trans pump I want to do so. I just need some help understanding if what I’m experiencing is normal by someone that has ran these machines before (I never have, it’s my first dozer). and if it’s not normal what can I test and repair to get its full potential.
any help out advice will be greatly appreciated. Thank you
Daniel Sosebee.

 

[Nige]

Here are a few thoughts. Others may have differing opinions.

- on start up, I put it in gear and it won’t move, but after it warms up a bit I can give it about 3/4 throttle and it will start moving. Once I get it to go that first time it does pretty good and will work without the hesitation that it has that first time after startup.

How long are you giving it for the systems to warm up before putting it in gear the first time.? With a tractor of that vintage warm-up is important, 15 minutes or so maybe. A good idea is to do the daily greasing and inspections once you have the engine running - obviously check levels before starting.
Do you know what type/grade of oil is in the transmission.? When you check the level does it smell burned and is it dark in colour, or is it clear and bright.? How do you check the level.?

- when Pushing dirt it does pretty good in first and second gear but if I shift into third it will lose speed and seems weak in third. I always push a heavy load in first gear but my question is, is this normal to lose speed/power when shifting into 3rd under a load?

IMO the blade should be nowhere near the ground if you are in 3rd gear. Unless you are doing really light grading work it shouldn't be anywhere near the ground in 2nd either.

Attached are some specifications. Try testing pump, speed clutch and direction clutch pressures for a start and come back with your results. Pay special attention to how the pressure gauge behaves when you shift from neutral to any gear or between gears. Does it drop significantly (in which case how long does it take to recover.?) or does it simply flicker.?

 

[Mark250]

my thoughts on this
Has the filters and screens been checked? oil discolored/ burnt?
check your oil transmission oil level with machine running
remove floor plate under your feet and visually check for correct operation
remove linkages from transmission levers and confirm each detented position
if problem not found by this stage remove remove top plate from transmission and check spool adjustment as per instructions posted by nige in the test procedures
if ok install pressures gauges and perform transmission stall Test while watching the drive shaft between converter and transmission
usually with high hour machines the trans pump is weak or the suction hoses have gone hard causing prime issues

 

[John C.]

The pump is losing prime because there is an air leak between the suction frame and the pump. It could be a leaky hose where it connects to the rear frame, leaking suction strainer basket if it is mounted by the pump. Sometimes people pull the plate off the top of the strainer and forget about putting a new O ring back in there. Many times the pump itself is going bad and isn't very good about displacing the air. There is usually a plug in the pump used to plumb a gauge into. I have put a petcock in that and used it to bleed the air off. Start the engine and once you get a squirt of oil out the petcock, the pump will work. Having to do that usually means the pump needs to come apart for inspection and possible replacement. Doing the job right means pulling the belly pan and checking and possibly replacing all the hoses and clamps in the piping up to the suction port on the pump.

Good Luck!

 

[Nige]

Do you have any Operation/Parts/Service manuals for it.? If not then probably the first two ought to be top of your list with a Service Manual close behind them if you can pick one up at a good price.

Publication references so you can search for them. Prices are for a pdf download from Cat.
Maintenance - SEBU6662 ($30)
Parts - UE070095 ($124)
Service - REG00530 ($220 on CD. No download)

 

[tctractors]

The transmission filter should be drained down empty of oil before you remove the filter head along with the filter, on the top of the filter lid is a purge plug that needs removing to aid draining, this plug hole is a good place to hook in a pressure gauge (0 - 600 psi) as this would show you the top pressure, John C has the pump prime thing off pat as I would expect the bearings (bushings) are worn in your pump, it's only held on with 2 bolts and handy to get at, after market pumps often have the same warranty as CAT for way less coins, you can get the CAT bushings if they are found bad.
tctractors


p.s. keep out of 3rd gear, you never attempt work in this gear it is just for running light at reduced engine speed.

 

[Dave Neubert]

Check all your suction hoses make sure all clamps are tight I have tightened up the clamps before and fixed the problem also make sure the hosesare in good shape and the oring on the magnetic strainer is in good shape

 

[Milner Forestry]

Here are a few thoughts. Others may have differing opinions.
How long are you giving it for the systems to warm up before putting it in gear the first time.?

I always let it warm up for a decent amount of time before operating it, it didn’t really seem to make a difference on having to rev it up to get it to start moving. But I have some good news and an update. I finally got around to do some of the testing the guys recommended on this thread. First I cleaned the magnetic strainer and changed trans filter. This solved the hesitation from it going into gear that first time and having to rev it up to get it to start moving. That problem went away by changing the filters.

With a tractor of that vintage warm-up is important, 15 minutes or so maybe. A good idea is to do the daily greasing and inspections once you have the engine running - obviously check levels before starting.
Do you know what type/grade of oil is in the transmission.?

the oil looks decent, I think probably a 10wt motor oil is what it is, I’m not certain though I haven’t changed it yet.

When you check the level does it smell burned and is it dark in colour, or is it clear and bright.? How do you check the level.?


It doesn’t look or smell burnt, I’m checking it with the engine running and in gear.


IMO the blade should be nowhere near the ground if you are in 3rd gear. Unless you are doing really light grading work it shouldn't be anywhere near the ground in 2nd either.

Attached are some specifications. Try testing pump, speed clutch and direction clutch pressures for a start and come back with your results. Pay special attention to how the pressure gauge behaves when you shift from neutral to any gear or between gears. Does it drop significantly (in which case how long does it take to recover.?) or does it simply flicker.?

I done this test and used your attachment to find the ports. Thank you very much for that.

here are my results:
- Pump tested at the Filter housing plug is 150 low idle, 350 just above idle. Drops to 100 when shifting for just a second and jumps right back up to 350.
-Speed clutch test has the same results as the pump test.
-Directional clutch at low idle is 90 and just above idle is 290, when switching gears drops to 100 then jumps right back up to 290.
I took it a step further and decided to do the torque converter output test the results from it are: With no load at low idle is 19psi just above idle is 25// under a load and stalled out in 3rd gear at half to full throttle I get a solid 22 psi. According to the attachment you sent me 22 psi is low for the torque converter output. If I get this output up to spec will it push harder?

Just another update from my original post. Ive been using this machine, it’s not weak I’ve just never ran any other dozer so I don’t know what I should be getting. I just think it should be stronger. I am able to stall it out on a tree in first gear at wide open throttle.
I shouldn’t be able to stop the tracks from spinning should I?

 

[Milner Forestry]

my thoughts on this
Has the filters and screens been checked? oil discolored/ burnt?
check your oil transmission oil level with machine running
remove floor plate under your feet and visually check for correct operation
remove linkages from transmission levers and confirm each detented position
if problem not found by this stage remove remove top plate from transmission and check spool adjustment as per instructions posted by nige in the test procedures
if ok install pressures gauges and perform transmission stall Test while watching the drive shaft between converter and transmission
usually with high hour machines the trans pump is weak or the suction hoses have gone hard causing prime issues

I haven’t checked the linkages yet but I will if you think I really need to. It shifts into all the gears

my thoughts on this
Has the filters and screens been checked? oil discolored/ burnt?
check your oil transmission oil level with machine running
remove floor plate under your feet and visually check for correct operation
remove linkages from transmission levers and confirm each detented position
if problem not found by this stage remove remove top plate from transmission and check spool adjustment as per instructions posted by nige in the test procedures
if ok install pressures gauges and perform transmission stall Test while watching the drive shaft between converter and transmission
usually with high hour machines the trans pump is weak or the suction hoses have gone hard causing prime issues

I haven’t checked the linkages yet because that seems to be working correctly to me it shifts into each gear and back into neutral like I think I should but if you feel strongly like this could effect my pushing power I will check it. One of my original issues of it not moving when I first put it in gear without Erving it up to get it to start moving went away after changing the filters. Now I’m just dealing with I want it to have full pushing power, everything I can get out of it. I can stop the tracks from turning by pushing on a tree in first gear at wide open throttle I’m don’t think I should be able to stall it out but I’m not sure do you know?
I decided to do the transmission stall test because you told me I needed to check it. My results were: Torque converter stall test- with no load and at low idle I have 19psi and just above idle I have 25// when stalled out in 3rd gear I get a solid 22psi even at wide open throttle. According to a pdf nige sent me this is low. Would this effect my pushing power? If it get this pressure up would it be stronger? How do I get it up?

 

[Milner Forestry]

The pump is losing prime because there is an air leak between the suction frame and the pump. It could be a leaky hose where it connects to the rear frame, leaking suction strainer basket if it is mounted by the pump. Sometimes people pull the plate off the top of the strainer and forget about putting a new O ring back in there. Many times the pump itself is going bad and isn't very good about displacing the air. There is usually a plug in the pump used to plumb a gauge into. I have put a petcock in that and used it to bleed the air off. Start the engine and once you get a squirt of oil out the petcock, the pump will work. Having to do that usually means the pump needs to come apart for inspection and possible replacement. Doing the job right means pulling the belly pan and checking and possibly replacing all the hoses and clamps in the piping up to the suction port on the pump.

Good Luck!

With one of my initial issues being resolved being that it won’t move without 3/4 throttle initially to get it to start moving was fixed by changing the filters, do you think I still may have a suction issue? Now mainly what I need to do is get the machines full pushing power out of it. It’s pretty strong but I think it should do more. I can stop the tracks from spinning in first gear at wide open throttle, is this normal? If it is it maybe it’s good to go I just feel like it should have more.

 

[Milner Forestry]

Do you have any Operation/Parts/Service manuals for it.? If not then probably the first two ought to be top of your list with a Service Manual close behind them if you can pick one up at a good price.

Publication references so you can search for them. Prices are for a pdf download from Cat.
Maintenance - SEBU6662 ($30)
Parts - UE070095 ($124)
Service - REG00530 ($220 on CD. No download)

I don’t have any yet, but I think you guys have enough knowledge to help me get the old girl up to par.

 

[Milner Forestry]

The transmission filter should be drained down empty of oil before you remove the filter head along with the filter, on the top of the filter lid is a purge plug that needs removing to aid draining, this plug hole is a good place to hook in a pressure gauge (0 - 600 psi) as this would show you the top pressure, John C has the pump prime thing off pat as I would expect the bearings (bushings) are worn in your pump, it's only held on with 2 bolts and handy to get at, after market pumps often have the same warranty as CAT for way less coins, you can get the CAT bushings if they are found bad.
tctractors


p.s. keep out of 3rd gear, you never attempt work in this gear it is just for running light at reduced engine speed.

I hooked the pressure gauge in this pressure port and I’m getting: Filter housing port test- 150 low idle, 350 at just above idle. It Drops to 100 when shifting gears for just a second and jumps right back up to 350
Does this sound good or bad what do you think?

 

[Milner Forestry]

The transmission filter should be drained down empty of oil before you remove the filter head along with the filter, on the top of the filter lid is a purge plug that needs removing to aid draining, this plug hole is a good place to hook in a pressure gauge (0 - 600 psi) as this would show you the top pressure, John C has the pump prime thing off pat as I would expect the bearings (bushings) are worn in your pump, it's only held on with 2 bolts and handy to get at, after market pumps often have the same warranty as CAT for way less coins, you can get the CAT bushings if they are found bad.
tctractors


p.s. keep out of 3rd gear, you never attempt work in this gear it is just for running light at reduced engine speed.

I hooked the pressure gauge in this pressure port and I’m getting: Filter housing port test- 150 low idle, 350 at just above idle. It Drops to 100 when shifting gears for just a second and jumps right back up to 350
Does this sound good or bad what do you think?

 

[Milner Forestry]

Check all your suction hoses make sure all clamps are tight I have tightened up the clamps before and fixed the problem also make sure the hosesare in good shape and the oring on the magnetic strainer is in good shape

it’s possible one of those orings was sucking air, I thought changing the filters solved my issue of it not moving until I give it 3/4 throttle but could have been the orings.
Now I need to get it to push at its full potential. I think I have a low torque converter output pressure, would that make it not push to its full potential?

 

[Milner Forestry]

I tried to respond to everyone not sure if that’s the best way to go about using a forum like this if not I’ll get better.
i just want to thank everyone for sharing knowledge with me.
I want to get this thing to push hard. I’m thinking possible torque converter issues but I’m not sure. I read in a different thread that there is a relief valve that I can add or remove shims to get the torque converter output pressure up, it is currently at 22psi stalled out in 3rd gear at wide open throttle and I think that is low. Any advice or knowledge about this or what I should try next will be greatly appreciated.

 

[Nige]

I don’t have any [manuals] yet, but I think you guys have enough knowledge to help me get the old girl up to par.

You mean to say you can't afford $30 for a Maintenance Manual.? You'll be telling us next you can't afford to put fuel in it.

With one of my initial issues being resolved being that it won’t move without 3/4 throttle initially to get it to start moving was fixed by changing the filters, do you think I still may have a suction issue?

It's always possible. Did you remove and clean the suction screen while you were draining the transmission oil and changing the filter.? You did put new oil in it I hope.?
Checking the suction connections while cleaning the suction screen is easy and simply ticks off another box of "things done" to help further narrow down the possiibilities.

I decided to do the transmission stall test because you told me I needed to check it. My results were: Torque converter stall test- with no load and at low idle I have 19psi and just above idle I have 25// when stalled out in 3rd gear I get a solid 22psi even at wide open throttle. According to a pdf nige sent me this is low. Would this effect my pushing power? If it get this pressure up would it be stronger? How do I get it up?

You should get far more pushing power with a TC Out pressure that's closer to specification than the 22psi you have right now. I'd suggest to start by making sure you don't have any suction leaks. Once that box is ticked it will be time to move forwards.

I think I have a low torque converter output pressure, would that make it not push to its full potential?

You most definitely have low TC Out pressure. As above, start by fixing the suction side and cleaning the screen, or at least eliminating the chance there are any problems in that side.
Did you measure the converter inlet pressure or not.? I don't see any readings for that. Eliminate any possibility of leakage in the pump suction side then do the TC IN pressure would be my suggestion.