Thicker gearbox oil?
 

Hi,


I have an '03 R53 with a six speed gearbox. I changed the oil to Redline MTL. It shifts okay, but shifts noticeably smoother when it's cold than warm. Since it has 150,000 mile on it, I'm wondering if some slightly thicker oil might help. Is there something slightly thicker than MTL that wouldn't be too thick for the gearbox?


Thanks,
Eric

When it warms up, how does it act? Does it seem to grind gears at all? I do know that if you get grinding once the fluid has warmed up, it's a good indication that it's breaking down too quickly. What Red Line fluid did you use? The 75w80? How did it shift when you had the MINI fluid in it?

It acted about the same with the Mini oil. It's really difficult to shift into gear and change gears after its warmed up. I put in Redline MTL in it. I called Redline asking about using MT85 or MT90. If you look on their website, they're slightly thicker. The Redline tech said the thicker oil might help, but he said it could be clutch drag.

I've driven stick cars all my life, previously I had a 1991 Miata with a hydraulic clutch and several Hondas with cable operated clutches. I've also ridden a lot of motorcycles. The Mini clutch is very stiff and engages about an inch from the floor. It's always felt this way. It has 150,000 miles on it now. It had about 110,000 miles on it when I got it. As far as I know it had the original oil in the gearbox when I changed it a few thousand miles ago.

The Redline tech said that a dragging clutch would be especially hard to get into reverse. I haven't really noticed this. I did have the slave cylinder go out on the Miata and I seem to recall it was tough to get into gear, especially into reverse.

I don't notice the idle rpm dropping when I shift into gear when it's being hard to shift into gear, which I've seen with motorcycles when the clutch is dragging. I've taken the clutch apart probably 30 times on my Norton motorcycle over the years so i have a pretty good idea what clutch drag and slip feel like, at least on a bike.

Hm, personally, I wouldn't rule out a possible clutch issue. How many miles are on it? I've only really run into gear grinding issues when it's fluid related. I have a current vehicle of mine that acts the same and it gets tough to shift into some gears. I have to muscle it in at times. Definite sign that we will need to be replacing the clutch in it sometime in the near future. Not saying this is your issue, but just something I have dealt with. I'd also possibly suggest you check our your shifter cables and make sure they don't look damaged/corroded.

https://www.northamericanmotoring.co...-to-shift.html
https://www.northamericanmotoring.co...-engaging.html

seems very strange, would also think more clutch/engagement related vs fluids/gearbox

Know that a few folks have tried thicker MTL...
issue is shifting is very hard till it warms up in cold weather...
And I would fear that the lube is not getting where it needs to go...starving the bearings of lube...till the oil thins...

Going to a thicker oil imo is not the fix...

Think the clutch...and flywheel getting hot, expanding....is getting your shifts smoother...
+1 on getting to be clutch time....

Fixed my problem!
 

Hi,

I had noticed that the engine moved a lot when I loosened and tightened the drainbolts on the transmission. It looked to me like bottom motor mount was bad. I changed out the bottom motor mount and the top one. The top one I think was okay but I could see a crack or two in the rubber. The rubber in tgee small end of the bottom motor mount was pretty much shot. Changing the motor mounts transformed the shifting. I guess the engine/transmission was moving around and was tugging on the shifter cables, etc. The shifting is the best it's ever been. I got the car at 110,000 miles. It has 154,000 miles currently.

It is amazing how much of a difference properly working mounts will make on shifting and power transmission.

It really is.

Recently changed 2 mounts on my 5 speed Accord and it made feel like a completely different car.