I have seen plenty of answers to this question but none seem to fit my issue. As a result, I thought I would ask here: I have a 61 C10 Mod. It has a th350 behind a 350. I am having the age old problem of the transmission leaking, only after sitting for a few days. I have inspected every spot that would normally leak but only found one spot that is the problem. I put dye in and after it started leaking i.e. 3 days. It was leaking out of the kick down cable but not at the seal. It is actually leaking out of cable shield itself approximately 4-5 inches above the point where it goes into the tranny. Initially, I considered that the torque converter was leaking but there is no evidence when you take off the inspection where it bolts to the flywheel. No signs of leaking. I considered that the front pump seal might be bad but not sure that would create this problem since it is gear connected. So: What is your opinion and or knowledge expertise that is creating this problem. I will fix what ever it is but I don't want to pull the tranny out yet since I don't particularly like two piece drive shafts and besides, I am 73 years old and my body, although not leaking, is broken in many places. Too much time in, on, and around Helicopters that sometimes didn't fly. Thanks for the site and in advance, an answer to my question.
... My TH 350 has been leaking like that for years ... After sitting a day the torque converter drains down ... the fluid rises in the trans and leaks from the pump seal ... I only lose about a half a pint a year ... ... I like you have no desire to pull the trans to fix the problem ... so I keep a drip pan under it in the garage filled with oil dry ...
That is the same solution I have been using however, a leak is a leak and very irritating. If I get an answer that is valid, I will pull and fix just satisfy myself.
No Problem doing that but still don't understand WHY it would come out the kickdown cable unless fluid level too high. Is it normal for the torque converter to drain back and if not, what is the resolution? New Torque Converter and/or what seal?
It is pretty common for a TH350 to leak out of the highest point after a while. I don't know a sure fire way to prevent it...although I expect replacing the pump and converter, and making sure all the bushings and shafts inside are in good condition, will help. The 350 is notorious for wearing out pumps, shafts and bushings. And for leaking after sitting a while. The plastic on the cable housing gets brittle over the years, and starts leaking. A new cable should not leak.
I'll go with that and see what happens. May go to th400 later. Thanks for all the input. Have a good day.
My guess is that the converter is draining into the pan raising the fluid level thus leaking from the converter seal leak. My TH400 does the same thing after sitting for awhile.
Every th350 I had did this... My solution on my last one was to get into the car every day when I came home from work and start it and put it in gear for a min or so...keep everything moving and full. Sitting in the car listening to a small block run everyday was so much better than pulling the tranny. YMMV Chappy
My brother in law struggles with this and he's done a lot of research on it. We agree with the theory of the converter draining and then over filling the pan. A thought I had once was why couldn't you use a deeper pan in conjunction with the stock amount of fluid? Then when it drains back, it just would fill up the deeper pan rather than filling up to items where these leaks are occuring. The lowered pickup with the deeper pan would still allow fluid to be picked up as normal for operation.
The problem with running the stock amount of fluid in a deep pan is when accelerating or turning corners the fluid moves away from the pickup and then the transmission will slip just as it will when the transmission is low on fluid. That is not the way of correcting your problem. As far as I know there really not a way of stopping this from happening, and I built transmissions professionally for many years.
It was just a thought and you have a good point - didn’t think of that. Maybe some trap doors like some oil pans? Sent from my iPhone using H.A.M.B.
Jim, How many places where a T350 can leak from? Of course, the converter drains down. That's why you check them ,running. This one sounds like an easy fix
check the seal behind the shifter rod coming out the side of the trans, my leak for years till i was told this it was cheap fix
My three favorite spots to look for a leak - one you are past the typical spots - are the speedo cable 'O' rings, the shifter seal and the accumulator cover 'O' ring. The accumulator cover 'O' ring is very difficult to pinpoint because it is just above the pan rail and the fluid dribbles down to it. I stick my finger into the bottom of the recessed hole for the cover and see if its' damp, if it is then its an easy fix if you have the tool to break it down.
Tell me what’s the fix for the shift lever shaft leak? Two seals and mine still drips. Sent from my iPhone using H.A.M.B.
Most likely the torque converter is bleeding down. I had 3 different cars stored in my garage a couple years ago. a 350, 400 and 700r4. All 3 leaked during the winter. start them up and run them and good to go. Irritating, yes. What to do? Dont know.
put a big drain pan under the car when you park it for a while? the PG in my kid's car does this too. The best cure is to drive the thing all the time,
If you got deep scratches or cuts in the metal from getting the old one out, don't know what to tell ya
If the shift shaft is rust pitted or scratched up, it will leak.. A good used shaft or new shaft is needed. Sometimes the seal is cut when installed over the square edges. Hughes Performance manufactures a new shift shaft for the thm-350 trans. If the bore for the shaft is worn badly... the shaft side movement will cause leaks. A fix for that I have used is to machine a groove for an O-ring on the shaft to seal on the ID of the bore
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