Help! Need FMX trans leak opinions please.

[tkelley72]

I need opinions on whether or not to spend the time and money trying to fix a leak on my FMX transmission. From what I have read here and other places this seems to be a common problem. It's the typical "leaks after sitting for long periods without driving" and then suddenly stops. I've read that the torque converter bleeds down, filling the trans body above the shift shaft bushing and seal, and leaks out from there. Once the level gets below that point the leak stops.....makes sense to me. I have also read where several people have gone to the trouble of replacing the bushing and O-ring only to have it leak again in relatively short period of time. So my dilemma is this.... I'm not as young as I use to be and am unable to crawl around under these things like I use to so I would have to pay to have this done. I'm sure the cost to do this would not be cheap. I know the parts are cheap ($10 bucks or so) but not the labor at a trans shop. So is it really worth the gamble that 6 months down the road I could be right back where I started? Sorry to be so "long winded" but I wanted to put out there what I know about the problem. Any and all opinions would be greatly appreciated. Thanks everyone!

 

[TheRktmn]

My FMX did that, as does my C6 if it sits for long periods (like a New England winter). My 85 GMC with T350 will leak too. Starting and letting them idle to refill the converter seems to prevent that.

 

[Ron Tanzi]

I have the same issue with my FMX. I have had the seals for over a year but have not pulled the trigger on fixing it. Otherwise for a 50+ year old transmission with 158K mikes on it and that has never been apart it works fantastic. I am reluctant to drop the valve body which is required to replace the shaft seals. I have a surplus of cardboard for now to keep my garage floor from getting trashed. To your quandary re: will it leak again in 6 months. If the selector shaft is badly worn where it contacts the seal it could leak again unless the shaft is either reconditioned (if possible) or replaced (not easy to find one). You will only find that out if you take it apart. If it leaks really bad I would roll the dice and have it done.

Ron

 

[jscott]

Mine also...................but with old rides................if it ain't leakin it must be empty!!

 

[giantpune]

You could think about it like a math problem.

How much will it cost to pay somebody to fix it? Shop probably wants $500+ just to crack open your transmission.
How much does it leak in transmission fluid if you just park the car and let it leak?
How much does it cost in gas to crank your car up and let it idle often enough to keep this from happening?

Of those 3, the cheapest option is probably crank the car up every so often. Next would be just do nothing and let it leak, then spend the $5 and put a quart of fluid in it each spring.

What you could also consider is one of those vacuum fluid pumps. Drop the tube down your dipstick hole and pump out a couple quarts before you park the car for the winter. That way you dont have to clean up any mess next spring.

I'm all for fixing things the right way. But if you're gonna pay all that money for labor with no guarantee it'll fix the problem long term, I'd probably consider one of the other options instead.

 

[Sheriff41]

I'm not a big fan of additives but K&W TransX worked well in my old C6 when it had a small pump seal leak. Not a permanent fix but may hold you over until you can repair the transmission. I agree with starting and running until the fluid is warmed periodically.

 

[steves73]

Mine leaks from there too. I leave an oil change pan in the right spot to catch it. It's clean, so I could re-use it, but I just top up with new fluid.

 

[Tnfastbk]

https://www.napaonline.com/en/p/BK_...TvbjBx3wswviEAQYAyABEgJS-vD_BwE&gclsrc=aw.ds&

 

[tkelley72]

Wow... all great responses. I have been leaning towards leaving well enough alone as I have been doing for years now. The leak isn't horrible, and I keep a shallow baking pan (my wife was excited about that!) under it at all times. Guess I'll just keep doing that and top it off when needed. Other than the leak the trans performs perfectly. Thanks to everyone for your opinions. Think I'll keep my cash for crusing.....

 

[Mac]

I can feel your pain. Having lived with a car that had a trans leak that kept getting bigger. Searched around locally for dealers/repair shops for help and being turned down, I decided to bite the bullet and give it a try while we were all staying home due to covid.

Never worked on a trans before, but I figured to give it a try. Jacked my car up on jack stands in my garage and got out my digital camera. Ended up writing a "how to" article mainly to help myself put things back together later.

Really wasn't too bad to do using regular hand tools to take apart and reassemble. Worst part was getting the shifter poppet in place as it is held in place with a spring behind it and its upside down so you are working against gravity.

Total cost was about $80 (seal, o-ring, pan gasket and trans fluid). I did this in May of 2020 and so far no leaks and the trans shifts just fine.

If your interested, look at my write up. It's in the General Maintenance Forum on the web site under Changing a shifter seal and o-ring on FMX trans written by "Mac".

Good luck,
Mac

 

[tkelley72]

I can feel your pain. Having lived with a car that had a trans leak that kept getting bigger. Searched around locally for dealers/repair shops for help and being turned down, I decided to bite the bullet and give it a try while we were all staying home due to covid.

Never worked on a trans before, but I figured to give it a try. Jacked my car up on jack stands in my garage and got out my digital camera. Ended up writing a "how to" article mainly to help myself put things back together later.

Really wasn't too bad to do using regular hand tools to take apart and reassemble. Worst part was getting the shifter poppet in place as it is held in place with a spring behind it and its upside down so you are working against gravity.

Total cost was about $80 (seal, o-ring, pan gasket and trans fluid). I did this in May of 2020 and so far no leaks and the trans shifts just fine.

If your interested, look at my write up. It's in the General Maintenance Forum on the web site under Changing a shifter seal and o-ring on FMX trans written by "Mac".

Good luck,
Mac

Thanks Mac......I'll take a look at it.