mystery AT fluid loss

[johnsongang]

I just picked up a 90 B2 with a 2.9 automatic and I am experiencing a transmission fluid leak, but no detectable place where its coming from. Everyday, I need to add 2-3 ounces to keep it in the cross-hatched area on the dipstick. One theory I have: its been sittin for close to 7 years beforeI got it and I'm thinking a seal has dried out somewhere. I've wiped everything down, parked it on cardboard overnight and still cant find out where the fluid is leaking out. Can it be internal somehow?

 

[kimcrwbr1]

If you have a 4X4 it could be leaking into the transfer case check it for overfull otherwise keep an eye on it it will show it`s face.

 

[kimcrwbr1]

Is there a leak at or around the radiator or oil in the coolant?

 

[tcranger]

also idk if that trans has got it but some trannys have a vacuum modulator on them for a load signal from the engine if the diaphragm is ruptured or leaking the engine will pull trans. fluid into the engine and burn it and you will never see a drip

 

[johnsongang]

Is there a leak at or around the radiator or oil in the coolant?

No, I checked the trans cooler lines and they are completly dry and no trans fluid in the radiator.

 

[Earl43P]

also idk if that trans has got it but some trannys have a vacuum modulator on them for a load signal from the engine if the diaphragm is ruptured or leaking the engine will pull trans. fluid into the engine and burn it and you will never see a drip

^^^ Exactly.

The modulator is on the side of the transmission.
It has an engine vacuum line going into it (rigid tube, then rubber hose connection).

 

[blh0007]

yeah i had the same problem... i replaced the modulator and problem solved... by the way since we have brought up these vacuum modulators. i have an adjustable one. what does it adjust when you turn the screw in vs turning it out? sorry to jack your thread.

 

[dentond]

Hey, I was curious if you have figured this out, sounds just like the problem I am having. I don't think my truck has the modulator though. I think I read somewhere they don't use them anymore but correct me if I am wrong.

Just picked up the truck from a guy who owned if for 10 years (and said it had no problems... my butt).

The truck is a 1994 Ford Ranger 4x4
4.0L V6 with a A4HL Tranny

 

[hondaxr650]

yeah i had the same problem... i replaced the modulator and problem solved... by the way since we have brought up these vacuum modulators. i have an adjustable one. what does it adjust when you turn the screw in vs turning it out? sorry to jack your thread.

I have an adjustable one in the C4 in my Fairlane. Turning the screw in raises the shift points, backing it out lowers them if I remember correctly. Haven't driven or messed with it in 15 years or so but I think that's how it worked.

 

[dentond]

@Johnsongang

Turns out my truck does have a vacuum modulator. I found it last night and pulled the vacuum line off and sure enough transmission fluid ran out.

I think it would be a good idea just to pull the vacuum line if you have one and see if fluid comes out.