3CX transmission issues?

UnclejakeNZ · Post #1 by **UnclejakeNZ** » Mon May 29, 2023 9:09 am

Folks, I have a non turbo black cab JCB 3cx ~ 1988. It has about 5,000 hours on it as has been receiving some love lately, but there is obvious blow-by from the engine crankcase so I assume the compressions (untested) are low. I live on a remote island and it can take six or seven weeks to get even simple parts.

One job yet to be started is investigating poor driving thrust. The machine needs a great deal of throttle and revs to climb even a gentle slope. I don't have a working speedometer (yet) but I estimate full speed on the flat to be about 20kmph. The forward/reverse shuttle seems to operate perfectly. The four mechanical gears all seem OK and 4x4 works too.

The previous owner says he replaced the transmission fluid the week he sent me the machine but the workshop manual is a bit ambiguous regarding trans fluid levels. I have ordered trans filters and some ATF but they will not be here for weeks

Question: On a cold machine with the engine not running the ATF level is perfect on the dipstick (hard to read as the trans fluid is so clean), but checking the warm fluid level within 15 seconds of shutting down the engine shows no ATF on the dipstick. I wish I could just top up the transmission fluid and rre-test drive performance but I have virtually none available. Could the 'weak' drive be caused by something as simple as low trans level?

essexpete · Post #2 by **essexpete** » Mon May 29, 2023 3:01 pm

@agrimax may be along to advise but I think you check that era of syncroshuttle with the engine stopped. I think you could use any good quality ATF if the spec one not available.

agrimax · Post #3 by **agrimax** » Tue May 30, 2023 1:10 am

That's right pete. Checked when cold with the engine off.When the oil is low,they usually just don't drive at all. You could remove and wash the internal suction filter (adjoined to the flat plate with two bolts down below the spin on filter) and see if it helps but poor pushing power is more likely to be from a weak torque converter and transmission pump.

UnclejakeNZ · Post #4 by **UnclejakeNZ** » Tue May 30, 2023 9:11 am

Thank you gents. Not quite what I had hoped to hear, but I am grateful for the advice.

UnclejakeNZ · Post #5 by **UnclejakeNZ** » Fri Jun 02, 2023 10:17 am

To update the thread: Adding some ATF to the system to bring the fluid level up to the top mark 15 seconds after engine shut-down did nothing to improve trust.

Next step = pulling out and cleaning the suction filter Agrimax mentioned, but I am not optimistic.

The last step will be just putting up with lousy thrust until the machine just doesn't move. Ha!

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