cat d8l transmission trouble

[naheed]

serial number 7yb 00800.
having major issues with my dozer. stopped using it because it was unable to work.
as you shift into first gear, it doesnt engage you need to rev it quite abit to engage it and move and once its moving if you reduce rpm the gear feel like its gone back into neutral.
touched the transmission pump it was quite hot, i feel the pump has lost pressure!
checked the transmission filters at the back they were ruined looked like the pressure had sucked them in.
any ideas what could be wrong?

 

[naheed]

something wrong with the torque converter?

 

[Nige]

Remove the floor plate in the cab. Below it you will see a short drive shaft between the torque converter and the transmission. with the transmission in neutral the shaft should be rotating, when you engage gear it should stop turning immediately. Does it..?

 

[naheed]

yes i did notice that and yes prop shaft turns when in neutral and immediately stops when any gear is engaged.

 

[Nige]

So that would appear to rule out a slipping transmission clutch and suggest that the problem might lie in the converter.

 

[Bob/Ont]

Go through everything you describe in first post, watch the drive shaft between converter and transmission and tell us what happens.
Later Bob

 

[Nige]

Just reading your first post again. The oil goes from the outside of the filters to the inside, so a blocked filter will collapse inwards if the bypass spool is stuck or if it has the wrong spring in it for the filter Part Number you are using. Did you replace the filters with new ones..? Did you try cutting the old filters open to see what type of material was inside them..?
Try checking the filter bypass valve to ensure that at least the spool moves smoothly.

 

[naheed]

could you please direct me where the bypass spool is?
i will check that. my dozer got a job outside the city so im back today, old filters where numbered 1R-0719 paper type so the local cat dealer suggested i buy 4T-3131 they are metal type filters which i will change tomorrow or thursday when i go back.
checked the filters havent seen anything in them
cheers for the help much appreciated!

 

[naheed]

for future keep im also looking for a workshop manual

 

[Nige]

could you please direct me where the bypass spool is?
i will check that. my dozer got a job outside the city so im back today, old filters where numbered 1R-0719 paper type so the local cat dealer suggested i buy 4T-3131 they are metal type filters which i will change tomorrow or thursday when i go back.
checked the filters havent seen anything in them
cheers for the help much appreciated!

Dealer is talking BS in my opinion. If a 1R-0719 is collapsing a 4T-3131 will collapse just the same way despite the metal structure. Also a 4T-3131 is designed for fire-resistant (water-based) hydraulic fluid. Regarding the old filters, you will need to cut a section of the filter media out and squeeze it in a vice to expel all the oil. Once the oil is out then open the pleats of the media up and look in the bottom of them for any type of material. If you find anything post photos so we can see what the material looks like.

Here is a typical illustration of a D8L transmisison filter. Yours may be slightly different but it will be similar. The bypass valve spool is #10, you find it behind the big plug #9. Just make sure it's free to move and the spring is not broken.

 

[naheed]

back tomorrow to the dozer.
yes i agree the filters also say for fire resistant oil, unfortunately thats our local dealers advice i will put in a complaint about that.
so should i go ahead with the 4T3131 filters? will they work with normal tc-30 oil?
thanks for the bypass info will check on valve before i put in the filters and start and also check for any particles in the old filters.
anything else i should look at while checking the above?

 

[Nige]

I would use the 1R-0719 if it was my tractor but before starting the engine for the first time with new filters installed I would be looking at the bypass valve in both filter housings.
I would also remove the screen at the bottom of the torque converter housing and check it for any material that might be blocking it. See below circled in red.

 

[naheed]

greats thanks will be on it tomorrow

 

[naheed]

wow big big relief huge thanks nige!!!!!!!!
checked bypass valves was hoping they were jammed but they werent thus put in the new 4t3131 .so checked torque converter strainer, it was clean and found 2 more strainers one was under the transmission pump a large one, that was clean aswell but the one at the back bottom of the transmission was completely clogged up looked like heated o- rings all around the strainer,cleaned that put in some new tc-30 oil tested the machine and ran superbly.transmission seems good running well with full power.
just had some issues with the dip stick at times it shows oil in operating range at low idle and sometimes it shows oil level about 4 to 5 inches above operating level!abit of confusion there trying to figure out why that happens?

 

[Bob/Ont]

With a clogged screen like that I think you have a transmission repair in the near future.
Later Bob

 

[lantraxco]

Just FYI, the dealer I worked at back in the late 90's, I was told that the filters for the fire resistant fluid were routinely installed as "cleanout" filters before CAT started making an explicit cleanout filter. They should just have a smaller micron rating to catch smaller particles, usually used after a contamination event to catch any missed contaminants remaining in the system. YMMV

 

[Nige]

Post a photo of what you found in the transmisison screen ......

If the trans screen was full of material then the filters were full also. Even if the filter bypass valve was in good working condition if there was enough material plugging the filter the bypass valve would not have enough oil flow capability to handle what couldn't go through the fiulter element. Ergo the filter collapses inwards under excessive pressure, it all fits the symptoms that you have experienced.

As Bob says, gird your loins - you have a transmission to pull ......... the only possibility I can see of the fact it's not an impending transmission failure is if the screen is full of material from a previous failure and was never cleaned at the time of failure/repair. A long shot but possible I guess.

As a suggestion let the new filters you installed run for a week or so then remove one of them, cut a section out of the filter media, squeeze it in a vice, then look in the bottom of the pleats and see what you can find. Here is a "how to" video. https://www.youtube.com/watch?v=3V-c-vAyrwo

Don, the 4T-3131 is for fire-resistant fluid but it's not listed as a cleanout element, that would be 4T-3132.

 

[naheed]

wow hopefully i will not have to do that soon as machine has been hired out for 2 more months!

 

[naheed]

unfortunately as i got back form the office the my mech had already cleaned the filter before i could take the picture.
but you can see some on the left side at the end. the whole strainer was covered in what seemed like melted rubber like material with some orings around it. dozer running perfectly now, as earlier i had noticed as you shift it into anygear youd have to get the revs up to get the gear engaged but now at even low idle the gear immediately engages as soon as you shift the gear lever!

 

[Nige]

All I can suggest is cross your fingers, change the filters again in a couple of weeks and see what you get out of them. See YouTube link in post #17 above for the method.

I hope you tried to "repair" the screen in order to get it back to a pretty-much circular condition before reinstalling it..?