RPM fluctations

vajper · #1 28th January 2021, 08:21 AM

This winter I have experienced some RPM fluctuations that I for some reason have associated with the gearbox. What I experience is that the motor RPM is moving between 1400-1600 rpm when driving on gear 3 and 4. It may be present on gear 5 too. This happens both when using cruise control and having my foot on the throttle.

The phenomena seems only to present after start, after driving for 15 minutes or so it seems to be gone. I have no fault codes that seems to be related to this (even though occasionally get an EGR fault code on one of the valves).

The gearbox is JEF, it has 280kkm on it and I'm pretty sure the transmission fluid never have been changed. I'm now considering my options. Can low fluid level result in these fluctuations?

If level indeed is low (plan to check that), should I consider changing the fluid? Not that keen on a full flush and not sure if it is worth it on this old car. OTOH I plan to keep it for a few more years.

steamship · #2 28th January 2021, 11:00 AM

Can't comment on the symptoms, but if it is low on oil, then best to top it up in accordance with proper procedures (temperature range), even if it doesn't eliminate the problem. As to doing a full flush that's a tricky one to answer. Some would say that the car has done 280k km and doing a full flush may dislodge gunk that could wreck the transmission, so best to leave alone.

ainarssems · #3 28th January 2021, 03:15 PM

No harm in checking fluid level or doing fluid change. Don't think you get any gunk settling in D3 boxes, modern fluids are keeping all the **** suspended in the oil, was only problem in older boxes that used older versions of gearbox oils.

I think it's just a software disengaging torque coverter lockup clutch as rpm drop. I have noticed on mine too but I would say more like 1200-1400rpm and more noticeable before it's warmed up while the fluid is thicker. Fluid has been changed on mine.

vajper · #4 8th February 2021, 08:13 PM

Thanks for the input, will check the fluid when the weather gets a tad less cold....

vajper · #5 12th February 2021, 07:45 PM

Looking at the instructions for checking the level it seems like one could change the fluid and filter while on it. Only part that seemed hard was how to get the wheels off the ground while running it in.

vajper · #6 27th February 2021, 08:36 PM

Have been driving the car in a tad warmer temperatures now and it's obvious the transmission doesn't change gears as it should when doing up-shift. It is like it is releasing the the torque converter but instead of shifting to next gear it keeps slipping too long which results in running this non-locked converter mode with too high motor rpm (lower gear).

Changing fluid is of course a good first thing to do but is there anything else I can prepare or check out to be prepared when doing the change? Anything else that commonly fail on these gear boxes like valves or anything? Have no fault codes when checking with VCDS at least.