Transmission Shift Cable Leak Repair on a 1957 300C

by Jim Krausmann
October, 2026





My C has had a transmission fluid leak for years. The main source of the leak was failed insulation on the gear shift cable where it meets the transmission. I had avoided repairs by adding fluid and keeping a pan under the car. The photo shows a last-ditch repair with a hose clamp. It didn't work.


Replacement cables are available but expensive and the cable I have works fine -- it just leaks. I read about installing heat shrink tubes in place of the insulation and liked the idea. They’re available from Quirey (quireyqualitydesign.com, page 24 of the old Goers catalog, item #678). The price is $31.40 and I bought a set.



While I hoped to not need it, I also got a transmission pan gasket. The Fel Pro for the C # is TOS 18333 and it’s available from RockAuto or the chain parts stores for about $10. Additionally, you'll find an O ring on the barrel of the shift cable. It might or might not be ok. I couldn't find an on-line source and got one from a friend. Take your old O ring to the auto parts store to match up for a replacement.


In the ideal situation, you release the cable from the transmission. The release as well as the installing and adjusting the cable is detailed in the C service manual on pages 279 and 287. Once you have the cable released, bring it up into the engine compartment, cut off the insulation, clean the cable and install two layers of heat shrink wrap. Reinstall the cable and adjust it if needed.

The "release the cable from the transmission" may be difficult. The manual says in order to release the cable, push the “1” trans button, remove a plug in the transmission, insert a screwdriver into the opening and release the spring holding the cable in place. You may spend a month with that screwdriver and never find the spring. If that happens, remove the pan and the spring will be accessible. I think cast iron torqueflites are largely the same. Don't have a manual? They can be viewed here: jholst.net Chrysler 300 Resources Page. Bob Merritt has an overview of the cable release at the club web site here.


For me, the job started slowly and took 10 minutes of screwdriver poking to get the cable released. Once released, it was easier to pull it up to the engine compartment for service than try to work on it under the car. Now I need to remove the old insulation on the cable. As a general note, anything more than 20 inches out and up from the transmission, the amount of insulation removed is only cosmetic. It was convenient and easy for me to go a few inches from the firewall. There's enough wrap included go the distance to the pushbuttons if you want to go that far. Before installing the wrap, I cleaned the bare cable with lacquer thinner. As a safety note, cover or disconnect the battery so the cable does not contact a terminal.


There are two layers of shrink wrap to install. The smaller first layer is snug going over the shift cable barrel and O ring. It was slow working it to the firewall. The directions that come with the wrap show the starting point on the barrel or see the last photo. I used a heat gun to shrink it, but the directions say a hair dry works. The second layer was also snug.


The photo shows the finished job. It's a close match to the original insulation. There is a layer of heat activated glue inside the wrap. It stuck well and I have no initial concerns about durability.


I got lucky on the re-install. The manual says to insert a screwdriver into the cable opening in the transmission and push the shift lever inside all the way back to low (easy, you can feel it move). Then have a helper press and hold the R button for maximum cable extension and insert it into the transmission. For me, it locked in right away. The in and out cable movement (gear selection and neutral safety switch operation) are adjusted by a slot on the support bracket (with the bolt in the photo). Part of the slot is visible. I tried to duplicate that spacing. I did not remove the neutral safety switch as the manual suggests and instead, connected an ohm meter to the neutral switch terminal and a ground. The meter had a reading from the start indicating the switch was connected. I didn't think there was a way I'd get this done without 10 layers of drama. Darn, it started in neutral and selected all the gears!


So, the summary, I don’t think the repair looks any different that the factory wrap, it is less expensive than a new cable and a new cable would require much more work at the push button end to install.


For the aluminum torqueflites there are some repair differences. According to the directions the thinner plastic cable insulation is not removed but covered, there’s a different starting point for the shrink wrap on the barrel (shown in the directions) and the cable adjustment method (in the service manual) is different.