Ford SD 6-speeds

mullins87

I have a low rpm noise in my tranny. The only way I can describe it is a "growl". This happens any time the engine is at or very near idle. It stops as soon as the rpm's begin to climb over appr. 850 rpm's. It never happens when the clutch is disengaged or when the tranny is in neutral. It happens when the clutch is being engaged, such as from a stop, or when I just slow down to idle speed and never touch the clutch. It does not seem to affect the noise what position the clutch is in, nor does it matter what gear it is in. I makes the noise whether the truck is empty or loaded. I have not taken the tranny out as I would like to rule out as many possibilities as I can before I wrestle that behemoth out of its mounts.

I've talked to several "experts" around here, but no luck. Can anyone help me with this?? Any suggestions will be appreciated.

0patience

Gonna need more info.
Like a year. 2 Wheel drive or 4x4?
When was the fluid checked in the trans?
Was it full?

mullins87

1999; 2 wheel drive; and it is full.

Someone told me I could fill it up to the top and since it is not a pressurized system that it wouldn't hurt to do that. I don't know about that, any comments?

0patience

Well, it won't hurt the gears, but it will push out the seals.
You see, as the fluid heats up, it expands, vapors form and the air around it expands. If the fluid were fill too full, then the pressure may be more than the vent can handle and push the fluid out the seals. Very messy.
Has it been checked for any metal in the case?
Isn't it under warranty?

mullins87

I don't think it's still under warranty, unless it goes beyond 100k. As for any metal, how do you do that without taking it apart? I figured the expansion of the automatic transmission fluid might be a problem. I most likely won't try it unless I can find someone who has done it without any trouble and can tell me how much extra fluid to add.

mullins87

Something interesting happened this week. The weather turned cold, below 40 degrees most mornings. When I first move the truck, no noise. However, the noise does return once the tranny begins to warm up. That suggests to me that the factory fluid, which is an automatic Mercon, is too thin for the application. Do you think a slightly heavier fluid might work and can you think of any reasons why Mercon would be used in this manual tranny??? One last thing, the tranny does have an automatic style cooler on it where fluid is pumped to the radiator and through a cooler. Other than the cooler, I can't understand why Mercon would be used. Just thought you might have some experience using fluids other than what is recommended.