Wowing auto transmission

[fubar]

Hi everyone I’ve owned my 100 for half a year or so 95k miles on the clock, a few minor repairs since buying it . nothing major. EGR block and driven about 5000 miles since

For a few months now have noticed an unusual sound phenomenon coming from the transmission from accelerating between 1200rpm to 1800rpm .. no unusual sound outside this rev range. The sound is a wowing, a steady and clear wow-wow-wow which disappears past 1800rpm.
If slipping into neutral the sound stops.
The fluid level seems ok but will check again. I’m doing a slow fluid replacement to synthetic after doing a full fluid change on my 80 ended in a flood on garage floor .. and ordering a new strainer to see if that helps but mystified what is causing the sound ..
any ideas anyone? Or any experience TC failure/damage
Thanks a lot

 

[uHu]

Not my specialty, but I do know how the fluid level should not be checked, which seems to be the problem in half the cases of LC auto problems. Is yours a 4 or 5 speed, dipstick or not?

 

[fubar]

Hello uHu appreciate the reply, it’s 4 speed 2001

 

[uHu]

Did you check the level on the dipstick while warm (normal operating temperature) and the engine running?

 

[fubar]

Fluid cold and engine running
when reinserting the cleaned dipstick and pulling out again the oil appears to thinly coat the dipstick up to hot maximum level but is that the real level? Will get tranny hot and check again .. the end of dipstick had a large drop on the end, probably just fluid collecting at end when pulled out not the level in the pan

 

[Ben Stratford]

Do you need to select each gear in turn when hot then return to N before checking level?
This charges the system first

 

[uHu]

Do you need to select each gear in turn when hot then return to N before checking level?
This charges the system first

Only if you have just changed (some of) the fluid. If you check level after a drive, which is the best time (while warm), there is no need to go through the gears again.

 

[fubar]

Will do a full fluid change plus strainer and report the results

 

[fubar]

New strainer fitted and no difference to the symptom noise but shifting between gears is crisp. Next step is a full on oil change, so far have added fluid to the existing using the change by dilution method,