jpc647

So a couple of weeks ago, I flushed out the radiator and it was decidedly very dirty.

Now I'm jumping into replacing a speedometer cable leak on a 1972 th-350. I can see it coming out of the cable. It drips. The wierd part is if I drive the car 200 miles and check it, it's fine. But when it sits for a week, there is a puddle on the ground.

If it sits overnight, no leak. 3 days or more, leak. Very Strange.

1) Where do I get the required seal(s) for this tranny?
2) Should I buy a can of the trans flush crap to get any crap out?
3) How many quarts of Transmission Fluid should go back in after I drop the pan. I assume some will stay in the torque converter, unless I have a drain on it. I'll drop the inspection cover to check, but I doubt it.
4) What transmission fluid do y'all recommend?

jaunty75

I've experienced this. I think what happens is that a seal that is starting to fail shrinks to the point that it allows leakage if the car sits for a few days with the transmission cold. But if you drive it every day, and the seals are heated regularly, expand, and then don't contract to the point that leaks start because you're in the car and driving it again before they've had time to contract too much, they do a better job of sealing.

This is one of the million reasons I give my wife when I tell her that cars like to be driven.


Have you tried your local auto parts store? This is a very common transmission.

http://www.autozone.com/autozone/par.../N-iptsnZ6o216

All I've ever done with transmissions is drop the pan and replace the fluid. Unless the transmission is failing and tearing itself apart, there shouldn't be any "crap" in the transmission. Where would it come from? It's not like combustion is happening in there and you've got combustion products accumulating. I can see replacing the filter if that's part of the normal transmission fluid change process. But if your transmission is working ok, I would just drop the pan, throw out the old fluid, put in new, and get on with life.

This should be easy to find in your car's owner's manual or certainly the factory service manual, which you can find at wildaboutcars.com. It'll tell you how many quarts are needed for a simple fluid change and how many for a full overhaul.

The manuals will tell you this, too, and I would just go to the local auto parts store and buy a good brand of that type of fluid. I think Dexron III was what was called for at the time your car was built. They're up to IV now, but it's backward-compatible.

http://www.autozone.com/autozone/acc...questid=594978

Redog

Yes, it's not a good idea to do a tranny flush, just drop the pan, change the filter and gasket and dump the fluid.

The fluid could be coming out while driving it, how does the bottom of the car look behind the tranny?

oldcutlass

X2 on what Jaunty said. You have a choice, if it's a small leak, I personally would not worry about it. However some folks are **** about putting a piece of cardboard under their car, then I would fix it.

OLD SKL 69

I hate trans leaks too. Had the same issue with the T-350 in my Cutlass. I replaced the O-ring in there and it still leaked a little. Took it apart again and added some silicone and that solved it.

jpc647

Thanks! I looked online at Autozone/Advance Auto but all I could find was the front/rear and the selector shaft seals. Not one specifically for the speedometer cable.

I should have worded my fluid question better. I guess I was wondering between the High mileage applications and the other, say, regular versions.


I'm sure a little comes out while driving. There is a couple of drops on the crossmember from time to time.



The cardboard under the car does not bother me, but when I moved the car and the cardboard was covered, I was a bit bothered.



Where did you buy the O-ring? How did you get the metal screw in type connector off the transmission? I tried vice grips, but could not get it to move.

NAS Backyard

As far as a flush, On my slim jim I drained the fluid,dropped pan, installed new fluid and filter, had out line to radiator/cooler unhooked into drain pan, started engine, let dirty fluid in trans to run into pan,(about a gallon) turned off, hooked lines back up, topped off, done, still clean. Fluid was DIRTY, I think it saved the trans. Bought the fluid in the gallon jug at Walmart.

Professur

Old thread but I'll throw my two cents in. Transmissions live by lubrication and friction. More than one person has had a good working trans suddenly quit after changing the fluid. The old one was worn out ... but the grit from the clutches suspended in the fluid was enough to keep it moving. Washing it out and putting new, very slick fluid in meant that the clutches just slid on each other now. If you're going to maintain a trans, you need to make it regular maintenance. In the trans system, you've got fluid in the trans body, valve body, pump, pan, TC and the radiator. Of the 3-5 gallons (yep, some take that much), maybe one gallon sits in the pan. There's a kick in the teeth, ain't it? Well, no fears ... we have a solution.

A good trans shop will have a fluid exchanger. By removing one line from the cooler circuit, they drain off the old fluid and add new at the same rate, getting the entire fluid volume in one go. They should also pull the pan off and change the filter at the same time. It's not cheap ... but it is through and clean (at least your hands are). You can do this yourself by disconnecting the fluid return line from the cooler (the usual method is to cut it, and put a rubber hose on it leading to a drain bucket ... and add fresh fluid back down the dipstick (trans dip stick, dummy) as it drains off. You need to keep close to the same pour rate as the drain rate ... this can get a little iffy. I know one guy who built a little system, where he put a balloon like bladder into the jug of fresh fluid, tapped the cap for 2 hoses, and put one hose into the bladder and the other into the fluid. The other ends of the hoses he put onto the cooler return. That way, as the fluid pushed out of the cooler into the bladder, it pushed fresh fluid out of the jug, down the return line and into the trans. (there's no suction on the return line, so you can't just suck it outta the jug.... that would be too easy) His widget did work ... but took so much time and effort, I really had to question the worth compared to just having the shop do it.

matt69olds

The reason it doesn't leak everyday is because when you let the car sit for a few days, the torque converter slowly drain back into the pan. Then the fluid level rises to the point where it will reach the speedo and/or dipstick o-ring and leaks. Drive the car regularly, the converter wont drain, no leaks.

For the speedo cable seals, go to your nearest trans shop. They probably have dozens of those seals. You need to be aware that some speedo housings have a internal seal that cant be replaced, you need to replace the complete housing. The speedo cable has probably rusted to the speedo gear housing, use lots of PB Blasted and some vice grips to get it loose.

TH350 trans are pretty durable, if it works good now just replace the fluid and filter. Hopefully there wont be a lot of debris in the pan.

Any current trans fluid would be better than what was called for when the car was new. Just get a couple gallons of Dexron fluid, it will probably take 5 or 6 quarts, depending on how long you let the fluid drain.

LJ72Cut

Did you apply the silicone around the dipstick tube once you inserted in the hole in the transmission or did you put the silicone in the actual dipstick tube hole in the transmission then put the tube in? I am torn between which way to do it. Currently I have my pan off. I had to dump my fluid and now looking to get a pan with a drain plug and the correct 27inch dipstick tube that does not bolt to the bell housing.

Ozzie

If all is correct the O ring should make the seal. Don't put any stray silicone inside the transmission. If you can't find a pan with a drain you can buy just the drain and install it in your pan. The best way is to get a bung and braze or weld it in to avoid leaks.