I have a 94 4Cyl with the Mazda 5-Speed Manual Transmission. Here's the deal...

I've owned this truck for the past 145K miles and the transmission has always leaked. I didn't worry about it in the beginning because the leak was very minor. Up until about a year ago I lost about 1qt about every 3 years, but now it is getting much more severe. I've cleaned the transmission several times and the leak seems to be coming from the cover on the top plate that holds the shift rails. I know there is a problem with the shift rail plugs, but not on mine (I've kept a very close eye on them and they seem fine). On halloween I changed my clutch and while the transmission was setting on the tailgate I decided that I would *fix* the leak! I took the cover off and spread some permatex around the cover (where the leak was) and also around the shifter (the one in the cab!). Since doing that the leak seems to be more severe. So...

Transmission Oil expands when hot, that means that the internal pressure inside the transmission increases...Is there a valve or something else that is used to release the increased pressure? In my mind, the pressure that is built up in the transmission by just normal driving would be enough to blow out a gasket (if it was completely sealed up), maybe I'm wrong I don't know.

Anyone have any ideas? Thanks

 

have you checked the shift rail plugs?

 

Well, I'd still focus on the shift rail plugs or the gasket on the top cover plate. As for pressure building up inside....naw, there's a vent somewhere to address that. You said "I took the cover off and spread some permatex around the cover (where the leak was) and also around the shifter". By that, do you mean that you had the top cover plate off? Regardless, why not try to tighten the bolts on the top cover plate down a bit more, assuming that is a suspect area. Yeah, I know, they are tough to get to and I know you can only give it your best shot.

Really, the shift rail plugs are the most common issue. You mentioned that you don't think your shift rail plugs are the problem; I'm just wondering how you ruled them out. Have you been up in there with a mirror and a flashlight after totally cleaning off the tranny?

 

Like the others said, shift rail plugs. On of Ford's worst designs ever. Over the years ths plugs harden and crack hense the leaks. I have heard that there is a "small parts kit" that replaces the plugs with metal caps. The other place to check is where you said you did, is the seal on the cap up top where the shifter goes in. Ther 3 torx bolts and a thin gasket under the cap.

 

The shift rail plugs are fine, I know there is an issue with 'em. But like I said, I've had the transmission on the tailgate and they look fine, doesn't even look like they have leaked a drop since Ford installed them. I think it's the top cover, just can't seem to get it sealed up too well. It's almost at 200k and still runs okay, guess I'll just keep adding oil!!!

Thanks guys

 

before you rule out the plugs, try to spin them around while they are in, if they spin at all, even a tiny bit, then they are bad. Good plugs won't budge at all.