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Any risk to overfilling transmission fluid?


westslope
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I know that overfilling motor oil is bad but how about overfilling transmission fluid?

 

I recently had the transmission flushed and refilled with synthetic GL-4 gear oil. It appears that the mechanic added ~0.8 litres of fluid above and beyond the recommend 5.1 litres of fluid.

 

Any risks? Should I empty some of the fluid?

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I don't think there is too much harm. A lot of ppl add and extra QT of redline to thier manual trans(after its already full) to make cold shifting smoother. The fill pulg will only let you fill so much before it spills back out of the tranny so overfilling requires lifinging one side of the vehile higer than the other, an overfil spout (aftermaket part that you prolly don't have) or remove the shifter (manual) and pour in form the top. chances are your mechanic did none of these he just filled to the plug and that ammount was "~0.8" more than the minimum reccmended level.

I'm sure other will agree that your fine.

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Yes overfilling a transmission is bad but I don't know how much over is bad...now I don't remember what the volume for nissans is (i know they misplaced the fill plug and you have to fill it from the top side to get the correct level)...so you may be at the right level

 

but if you overfill it increases friction/heat and I guess you could end up blowing some seals out too from reading around...I think its worse on an auto but not as severe on a MT...I know when I was working at FTL we had a lot of transmissions burn up from overfilled transmissions, most were auto but there were a few MTs in there but I am not aware of the mileage they had on them either.

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I talked to a bunch of people. Many reasoned that as long as the vent works and the fluid is close to ambient pressure, there is no danger of blowing out seals, or causing other kinds of damage. That was also the reasoning of the mechanic who thought that 5.1 litres was not enough.... and after glancing 2 seconds at the hard copy of posts and TSBs I printed from here, filled the manual tranny to a little shy of 6 litres.

 

He also claimed that since the Technical Service Bulletin (TSB)--which I showed him prior to flush and refill--targeted transmission whine, that 1990-1995 pathfinders with manual transmissions not exhibiting those symptoms, did not need to be filled beyond the 3.8 litre amount.

 

Frankly, I was not entirely impressed. Think about it. You wait for the problem to occur and then you fix it?

 

To the best of my knowledge there has been zero leakage from the transmission. So the 5.8 or so litres stay in.

 

Thanks for the feedback everybody. BTW, the 4th gear still sticks slightly unless I'm very careful to allow the RPMs to drop completely before shifting into 4th.

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my 95 was stubborn sometimes about going into 4th on a quick shift and sometimes about going into 1st...but after about 2-3 weeks of driving I figured out how she liked it and gave it to her that way...just like 2nd gear on my 87 in the winter time...have to go towards 4th and then into 2nd or she just wont go but once shes warm no problems at all

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Ours is smooth as butter when cold, and then may slightly stick going into 4th if one is not careful to drop the RPMs and hesitate slightly.

Edited by westslope
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I recently had the transmission flushed and refilled with synthetic GL-4 gear oil.

 

LOL, no... I too read your post and thought WTF? Nope, never seen a Pathy MT with a dip stick or an auto that runs on GL-4... :D

 

:itsallgood:

 

B

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I know that overfilling motor oil is bad but how about overfilling transmission fluid?

 

I recently had the transmission flushed and refilled with synthetic GL-4 gear oil. It appears that the mechanic added ~0.8 litres of fluid above and beyond the recommend 5.1 litres of fluid.

 

Any risks? Should I empty some of the fluid?

 

 

HEHE

 

It was the 'transmission fluid' that threw me off. Should have paid more attention to the GL-4 :itsallgood:

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