Greetings all. I have a question about the dangers of putting too much gear oil in a manual transmission. I know that overfilling an engine with too much oil is bad, but does the same apply to a manual transmission. I recently changed the gear oil in my '99 Maxima, took it for a test drive and the car drove great. However the next day the car felt a little sluggish.
Unfortunately, I'm a courier for my job and put about 80 miles on it that day before I realized what I might have done. To to change the gear oil I had to use a pair of ramps that I have not had to use for over 10 years. I poured in about 5 quarts of redline mt-90 into the transmission. I know it takes 4 and a half. While pouring the mt-90 in, the hose I used moved and alot of it went on the ground. Also none of it overflowed from the transmission after pouring in the 5th quart.
Later that day, on level groud and not using ramps, I drained the excess from the transmission. The car seems to drive better, but I was wondering if any damage had been done. Thank you for any comments.

 

Highly doubtful anything bad. First of all I'd be shocked if 5 quarts vs. 4.5 is bad, even long term. That's not much extra lube. In regards to engines, I think the problem is that parts of the engine are smashing around in the oil at very high speed, and it froths up. That's bad. In regards to a manual tranny though, pretty much everything is bathed in fluid anyway. I suspect that too much oil may reduce splashing of oil (think about when you shoot a hose in a bucket it squirts everywhere, but once the hose is submerged, it doesn't spray around as much), but over 80 miles you're surely fine.

Half a quart too little, or half a quart too much has got to be within safety.

 

in a manual transmission you have to fill until the fluid flow out.

 

It's impossible to overfill the manual trans.

 

It may not be bad for it, but it can definitely be overfilled above the drain plug, if you've got the car on ramps when you fill it up - you could squeeze at least an extra half quart in there. Hell, if you hang the car from its front bumper you could fit a couple of extra quarts in it.

 

I stuffed 5 bottles of 75w90 series2000 amsoil in my tranny, and there have been no problems.

 

But why would the car be on jacks when filling it up when you fill from the top of the trans through the engine bay? Also, 5qts is TOO much as well so I guess you can overfill it.

 

hmm, I guess it depends if you have a long enough funnel tube. Personally I had to jack my car up, so that I could get my wheels extended from the fender a bit, and then I managed to fit my funnel in a hole there and fill like that (the tube was fairly short). Then when i was full to the point it was dripping out I lowered my car so that it was on a perfect flat. Then when the dripping was finished I jacked it up again to put the fill screw in.

 

Can you explain to me how it is too much? What are the concequences?

 

It can't be overfilled because the manual tranny is NOT under pressure. Look at the tranny and you will notice a breather hose coming up to the front valve cover and attached to it by clips.

 

According to the 97 FSM the range to fill the M/T is 9.5 - 10.125 pts, which is 4.75 - 5.05 qts.