I think my manual transmission fluid is low. The gears grind at low RPMs when the car temp is cold. So I want to switch it out completely and replace it with reline mt-90. I don‘t know what the previous transmission fluid was, but is it necessary to do some kind of flush? Or should a simple drain and refill be enough.
It is far more likely you need a new clutch than it is you need transmission fluid, changed or not changed. Manual transmissions will run just fine on spit or a spoon full of fluid. Nearly every car with a manual transmission that was ever built went to the junk yard having never had the TX replaced and never having any fluid added or changed. Just for fun, the mechanic and I opened both gear boxes on my 1992 Suby with 230,000. Both were full and dripped fluid as clean as pure honey. Unlike your engine oil, no water, hydrocarbons or dirt are getting in and the fluid itself is not wearing out. Forget it and get the clutch replaced. Not a DIY. Tell mechanic you want the kit to be American made and plate ground smooth.
I commend you on your desire to do a thorough job on your manual transmission fluid change. There is no need to flush a manual transmission, simply drain and refil with the desired, highly over priced lube of your choice. Then, and perhaps only then, will you realize that changing the fluid will have absolutely no impact on the operation of your transmission. But, it will be fun hoping it will, and perhaps the placebo effect of the lube change will sustain you until the synchros finally fail entirely. Enjoy!
Drain and fill is all there is for a manual transmission. All the oil drains out, as opposed to less than half for an automatic. Be sure to loosen the fill plug before draining the oil to avoid the embarrasment of having an empty gearbox with a jammed fill plug! As others say, it sounds more like the clutch dragging. Testing is easy - with the engine and transmission cold, put the transmission in first gear, hold down the clutch and start the engine. Keep the clutch down while you shift into neutral and gently try shifting back into first. If the gears grind the clutch is dragging. If not, the trouble is in the gearbox.
it should be something not installed correctly. Re do it and see if it fixs your poblem.
