Leaky 700r4

[tsr2185]

Finally crawled under the truck to inspect after having to add .5qt atf every ~1000 miles. Never showed obvious leaks on ground when parked. Noticed the pan cork seal was crumbly around the edges and wet all around. Torqued bolts down for now to compress whatever seal is left until I get a kit ordered. I know I need a new seal and filter kit. But also noticed what I believe is my outlet cooler line going to the radiator has a hose with hose clamps on it. Both ends of the hose had oil all over caused atf all over the front of the pan and what not. The return cooler line is solid and seems good.

Question is, should I just replace this hose with new clamps, or is it wise to replace the whole cooler line? My concern with replacing the whole line is I heard horror stories or stripping the fittings at the radiator and a giant PITA to get the threads started on the transmission.

Transmission has been solid and haven't had any issues with it since I owned it the past year.

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[Schurkey]

SCRAP THAT HOSE if there's any chance it's ordinary "fuel line".

I've had to make some repairs to trans cooler tubes over the years; ideally the whole tube gets replaced. In this world, the usual fix is a (generally 5/16) compression union across the "bad" section of tubing. If a longer piece of tubing needs to be spliced-in, use two compression unions. Don't use copper tubing!

A better fix is to slide on a couple of tube nuts, then double-flare both ends of the tube; use a brass inverted-flare union. Yeah, this is better than compression unions...more work, though. Again, if you need to splice-in a longer section of tubing, you'd use two inverted-flare unions and four tube nuts and four double-flares.

I've never had a failure of a compression union on a trans cooler tube. However, be advised that ATF is surprisingly flammable and the tubes route very near the hot exhaust manifolds.

Compression union, inverted-flare union, or just replacing the entire tube--any one of those is better than rubber hose held on with crappy worm-gear hose clamps. We can already see in your photo, the rubber hose extruding through the slots in the clamps. It'll only get worse.

There's a dozen leak-points on an automatic transmission, and most of them can drool down and look like a pan gasket leak. Be sure you're fixing the "real" leak.

 

[tsr2185]

SCRAP THAT HOSE if there's any chance it's ordinary "fuel line".

I've had to make some repairs to trans cooler tubes over the years; ideally the whole tube gets replaced. In this world, the usual fix is a (generally 5/16) compression union across the "bad" section of tubing. If a longer piece of tubing needs to be spliced-in, use two compression unions. Don't use copper tubing!

A better fix is to slide on a couple of tube nuts, then double-flare both ends of the tube; use a brass inverted-flare union. Yeah, this is better than compression unions...more work, though. Again, if you need to splice-in a longer section of tubing, you'd use two inverted-flare unions and four tube nuts and four double-flares.

I've never had a failure of a compression union on a trans cooler tube. However, be advised that ATF is surprisingly flammable and the tubes route very near the hot exhaust manifolds.

Compression union, inverted-flare union, or just replacing the entire tube--any one of those is better than rubber hose held on with crappy worm-gear hose clamps. We can already see in your photo, the rubber hose extruding through the slots in the clamps. It'll only get worse.

There's a dozen leak-points on an automatic transmission, and most of them can drool down and look like a pan gasket leak. Be sure you're fixing the "real" leak.

Do auto stores provide the 5/16" compression unions and tubing? Is this a specialty item or something I can grab at any auto store?

I was planning to replace with trans cooler hose and some FI clamps. If these compression fittings and tubing are easily acessible, I will go that route.

As for the pan, I have no idea the status of the filter so I planned to go ahead and change that out. I will inspect above the pan line next time I get a chance to climb under there.

thanks schurk!

 

[Schurkey]

Auto parts stores or any decent hardware/home-improvement store (or Amazon) will have compression unions. Inverted-flare unions probably the auto parts store or Amazon only.
www.amazon.com/Dorman-800-142-Steel-Compression-Union/dp/B0049DXMZY/ref=sr_1_5?crid=113IPYV2OEFHN

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www.amazon.com/Inverted-Flare-Brake-Union-threads/dp/B01KNGVFZ4/ref=sr_1_1?crid=25I2HAYF7WEUX&

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Tubing "sticks" are in any auto parts store, variety of diameters and lengths. Sold as "brake" or "Fuel" tubing--double-wall, seamless steel. Sometimes coated for rust prevention, more-often bare. Measure your tubing before you start--a few vehicles have 3/8 cooler tubes, but most are 5/16. I suppose four-popper penalty boxes might have 1/4" or metric tubing.

 

[stutaeng]

Yes, I got some of those compression fittings and the coated brake line at O'Reilly to extend one of my transmission cooler lines when swapped my transmission. I think mine were 3/8".

I cut off the ends of the brake lines with a copper tubing cutter. Sanded off the coating exposing the bare metal alloy (I don't know what alloy it is) and went to town. I've checked them several times and they don't leak. Flared fittings maybe were a better option?

What pressures are in those lines anyways? It's not the full hydraulic transmission pressures from the transmission, is it?

 

[Schurkey]

Anything over 80--90 psi is a problem in the cooler circuit. Overloads the crankshaft thrust bearing because the cooler circuit reflects the pressure in the torque converter--and pressure in the converter tends to slide the converter "forward" into the engine.

This is NOT "ballooning" of the converter. Just pressure pushing it forward, which has to be countered by the crankshaft thrust bearing.

 

[tsr2185]

Well to follow up....

For some reason the transcooler line hose was covering a freshly cut trans cooler line. Im guessing this was done during a cooler line install, or a new transmission install to make up easier. I just threw on a 3/8 compression fitting, and all has been well. Also, the pan was leaking due to a crappy cork seal. Replaced seal and filter and all good to go. Just glad it wasnt my rear main seal leaking....