Probably one of the easiest seals to replace on a TH350. It’ll take you about 10 minutes if you do it right. Now now..you dont go around telling the ladies how easy this is. What you gotta do is hype it up. First things first. Go get the biggest hammer you have, a sledgehammer is OK. Walk in to where your significant other is at, lay that bad boy down and sip on your favorite beverage while throwing out this task you’re fixing to tackle. If all goes according to planned, it looks like there’s some serious ass kicking thats about to occur. Yea, lay it down thick. Head on out to the garage, jack up that hotrod and then get the sledgehammer. Find a piece of metal laying around in the shop/garage and take a few good whacks at it as if you’re trying to win some sort of strongman contest, your significant other will be impressed upon hearing that racket. Once you’re done, follow along in the pics on how to replace the seal.
You’re going to need two parts, a selector shaft seal, part # 1-3887 and the Selector Shaft seal removal tool, part #776-9250. I bought both from NAPA. Total price was around $10. Left side, obviously, the seal. To the right of the seal, the silver tool is the tap which goes over the shaft and will be used to install the seal. To the right of the tap is the actual seal removal tool which is threaded on one end and has a bolt on the other end.
Get under your car and remove the shift lever from the shaft by removing the nut on the end of the selector shaft. Just that. Nothing else. It will pop off and you’re done with that part.
Get the Selector Shaft seal removal tool and slide it over the selector shaft. Make sure its aligned so you dont scuff anything up. You may need to tap on it to get it to contact the selector shaft seal. Once on, get a box end wrench and screw it on to the seal until virtually all threads are thru. I had maybe 3 or 4 threads on the selector shaft seal removal tool showing.
Go get the bolt and screw it into the seal removal tool until it bottoms out on the selector shaft. Once there, get a box end wrench and tighten that bolt. This motion will cause the seal removal tool to remove the seal from the trans.
There…voila! Seal removed. Next up is installing the new seal. The tapered end, pictured below, goes first. You will use the supplied tap to install it. Pic on the right shows how it basically goes.
Slide the seal over the shaft and use the tap to install the seal. Make sure its aligned properly. Use a hammer to gently coax it in. It wont fall through into the trans if thats what you’re wondering.
Your install is complete. Just reinstall the shift lever and the nut. Drink a few brews and brag to your significant other.