Too much tranny oil & Diff Oil?
07-17-2006, 07:23 AM
#4
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If you do the oil change procedures properly, there shouldn't be any problem. The fill hole is your full line in both cases, so filling the reservoir to that level (oil will start to come back out of the hole at some point) is all that you need. More is not better because you have to allow for foaming space (just like in your engine) in the tranny and differential. Most gear oils have foam suppressants in their un-adulterated state, but the full level should be maintained and respected as an added precaution.
07-17-2006, 07:35 AM
#5
Originally Posted by INDYMAC,Jul 17 2006, 08:23 AM
If you do the oil change procedures properly, there shouldn't be any problem. The fill hole is your full line in both cases, so filling the reservoir to that level (oil will start to come back out of the hole at some point) is all that you need. More is not better because you have to allow for foaming space (just like in your engine) in the tranny and differential. Most gear oils have foam suppressants in their un-adulterated state, but the full level should be maintained and respected as an added precaution.
My gut feeling is AP1 trannys do better with a little extra (100-200cc) of tranny oil under extreme conditions. I very seldom hit extreme conditions but still I push it every time I drive it.
The rearend will blow it out the vent if there is too much and you will know from the mess. I manage to get about 50cc more in there.
07-17-2006, 07:37 AM
#6
Here's my take on this. Unlike the engine crankcase, the tranny and rear diff internals baths in the fluid anyway. An overfill in the engine results in the "big end" coming down and smashing into the top portion of the oil. This is what promotes foaming. In the tranny and diff, since the fluid is naturally covering parts of the internal components, there is no high impact of metal parts onto the surface of the fluid. Foaming is not nearly as prominent. We don't have any sort of high pressure pumping system in either casing. The tranny has a very low pressue, low output pump and the diff has none. The diff also has a breather hole on top in the event of too much fill. So far, in my overfills, no fluid has appeared in this vent.
In particular, our rear diffs are pretty small for what it's asked to do. It has considerably less fluid in it than most other rear diffs. We also know that heat can be one of the biggest enemies of the rear diff. I believe that a little overfill will act as a better heat sink and heat transfer mechanism.
Of course, "officially", I would tell you that "by the book", fill it only to the bottom of the fill hole, with car on level.
In particular, our rear diffs are pretty small for what it's asked to do. It has considerably less fluid in it than most other rear diffs. We also know that heat can be one of the biggest enemies of the rear diff. I believe that a little overfill will act as a better heat sink and heat transfer mechanism.
Of course, "officially", I would tell you that "by the book", fill it only to the bottom of the fill hole, with car on level.
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07-18-2006, 02:05 AM
#8
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Driving to work this morning I was thinking about this post....
As you can see there is a large "hole" connecting the rear of the diff to the front pinion bearing.
Note that the diff is lying up-side-down in the picture.
I'm thinking the ring gear is acting like a "sling-shot" and throws oil towards the front pinion bearing, acting a bit like an oil pump.
The oil level is below that ridge I think.
So IMO there is some oil circulation in the diff.
This only works driving forward.
Just a little more oil circulating in there sounds good to me.
(I did that too)
When you jack up the car at the driver side the filler hole is a bit more up in the air and its easy to get a little more oil in.
("driver side" works for left hand drive only )
As you can see there is a large "hole" connecting the rear of the diff to the front pinion bearing.
Note that the diff is lying up-side-down in the picture.
I'm thinking the ring gear is acting like a "sling-shot" and throws oil towards the front pinion bearing, acting a bit like an oil pump.
The oil level is below that ridge I think.
So IMO there is some oil circulation in the diff.
This only works driving forward.
Just a little more oil circulating in there sounds good to me.
(I did that too)
When you jack up the car at the driver side the filler hole is a bit more up in the air and its easy to get a little more oil in.
("driver side" works for left hand drive only
)
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