Disappearing transmission fluid and poor gas mileage

[molehole]

Hi everybody. I am posting this for a friend. He has a 1997 Bonneville Sle with 135k miles. He was telling me that it seemed like the tranny had something wrong with it. To make a long story short it was 3 qts low on fluid. I put in the fluid and it was shifting great. Problem fixed right? No not so easy- I was talking to him today and I checked the fluid for him. Sure enough it was low on fluid again. I checked the engine oil and realized that it is at an elevated level. My question is, is there a vacuum modulator that can malfunction and cause this? I had this problem with a Ford Explorer and the modulator was bad and when repaired fixed the problem. Am I right in my reasoning or am I missing something? Thank you for any advice- Mike

[maxwedge]

Originally Posted by molehole

Hi everybody. I am posting this for a friend. He has a 1997 Bonneville Sle with 135k miles. He was telling me that it seemed like the tranny had something wrong with it. To make a long story short it was 3 qts low on fluid. I put in the fluid and it was shifting great. Problem fixed right? No not so easy- I was talking to him today and I checked the fluid for him. Sure enough it was low on fluid again. I checked the engine oil and realized that it is at an elevated level. My question is, is there a vacuum modulator that can malfunction and cause this? I had this problem with a Ford Explorer and the modulator was bad and when repaired fixed the problem. Am I right in my reasoning or am I missing something? Thank you for any advice- Mike

Faces forward on the front of the trans, pull the vacuum hose and look for oil, but this would smoke like crazy if it sucked enough out to overfill the crankcase ( not likely).

[GTP Dad]

I agree with maxwedge! Check the area around the seals and look at the back of the engine around the torque convertor. It sounds like there is a leaking seal somewhere that is causing this issue. I would also check the radiator for signs of transmission fluid.

[molehole]

Could 2 quarts disappear like that within a week? Seems a little extreme for just a leaking seal. I will check the vacuum lines when i get a chance.

[richtazz]

I've seen modulators leak that much, but they normally suck the fluid into the intake and burn it out the exhaust, not into the engine oil. Is there any oily residue on his tailpipe? Trans fluid burns pretty completely, so there won't be much smoke. I've used it in the past as a fuel system cleaner (1 pint to 15 gallons of fuel, and since it's as much detergents as lubricant, it works excellent. I'll bet the inside of his engine is nice and clean now. The biggest issue is if it's getting in his oil, it's thinning it out, which isn't good.

[molehole]

Thanks for the advice everybody. I will check it out tomorrow.