I've been leaking ****** fluid everywhere lately. I've had the truck running a couple of months and the leaks have progressively gotten worse. I found that the tail shaft seal and the shift shaft seal are both leaking pretty bad and seem to be the main leaks here on the ******. Any advice on replacing them? I've read up on it some on the web. I have no manual and am going to just jump into it. It doesn't seem too difficult. I did read on a couple of forums something about a pin that needs to be remmoved before removing the shift shaft on the th400... is this true? ... Do I need any special tools? Can the rear pump seal be changed without pulling the transmission? I thought I might do this too just in case. Also, does anyone happen to have part numbers for these items? Thanks. KD
Most decent parts houses sell a special tool to help remove and install the shift lever seal. It is made by KD. I have one ( for years ) and it works great About 10 dollars at the store I buy at. The rear seal is simple to remove and install. Just remove the driveshaft, remove the seal ( I use a seal remover ) But a screwdriver does work ... Make sure you get the correct rear seal. Turbo 400's have different sizes ... in the output housing. All the shift seals are the same. Even Turbo 350, Powerglides and 700R4 use the same shift seals.
While you are at it also change the speedo gear seal and o-ring. A hint that helped for me was to have the rear end fairly high - helped from losing oil while changing the seals. ANother place that leaked on mine was the fill tube. Was okay till parked for a while and then the converter drained back and it leaked there. A new o-ring and some silicone fixed this.
Another thing to check on your yoke is if there is a small hole in the end, under the U-joint. Sometimes a hole where the center is can leak. Clean it good and a small dab of silicone solves that problem. If your output bushing is worn, then a new seal will leak in very short order. Make sure the yoke can not move up and down any significant amount. The oputput bushing is inside onece you remove the seal you can see it easier.
I might add you do not have to remove the shift shaft to replace the seal. Just use the tool to pull the old seal out, then use the other piece to drive in the new seal.I just did the very job lately.Had to borrow the tool,that was cheaper ,the tool on line is $40.00 .good luck Jobob
The shift shaft seal look kinda hard to get to from the outside. Can I just use a seal remover or pick to get it out or do I need to go from the backside?
$9.95 on eBay http://cgi.ebay.com/ebaymotors/GM-T...tZMotors_Automotive_Tools?hash=item4ceeda9486 The directions for the seal remover reads ... Removes and installs shift selector shaft transmission seal without draining fluid Works on G.M. Transmissions. Instructions 1 Disconnect Shift Linkage 2 Unscrew Remover Screw a Few Turns And Place Remover Over Selector shaft. 3. Push And Turn Remover Threads Into Seal 4.Turn Remover Screw Inward To Pull Seal. To Install New Seal 1. Put new Seal Over Selector Shaft 2. Put Installer Over selector shaft And gently Tap seal Into Place 3 Reconnect shift Linkage. You do NOT want to try and go after the seal from the rear. The pan would have to come off and then you are still looking at the valve body
I saw this from another forum... "First of all it is messy because you have to lay under the valve body to get it done, so be prepared to be rained on by trans fluid. Once you have the pan and the shift linkage off, put the nut back on the selector shaft - it will help you hold on to it. Loosed the detent roller and rotate it away so you have acess to the nut on the inside end of the selector shaft. Now you can see that there is a "pin" (looks like a finishing nail) that is parallel to the floor and is in the casting used to retain the slector shaft (it's about 1/4" away from the inner nut). If yours is the original, you'll need to cut it off as the casting on both sides of the valley will retain it. Get some big diagonal cutters, get a big grip on it and cut it. Try to stuff something in the cavity so that as it cuts it doesn't bounce up into the trans above the valve body. Pull the remaining piece of the pin out, then you can loosen and remove the inner selector shaft nut. The plate on the end is pressed onto the shaft, so you'll have to pry it a bit to remove the shaft . Youll notice the nut will hit the casting as you loosen this, but keep going as it helps pull the shaft out. Once the nut is loose, if the shaft is still tight use a screw driver and put it behind the outside slector shaft nut and the palm of you hand to drive the shaft out a bit. As Tony points out, there will likely be burrs on the inner shaft end where it's machined to register in the plate. Clean these off before you try taking the shaft out all the way as it could bind up on the casing as you try to slide it out completely. Once all is free, remove the shaft. Now the seal is in the casing and you can get to it with a screw driver to pry it out. Clean everything up, but don't put the seal in yet. ***ure the burrs are off the shaft and specifically off the register where the inner shaft mates with the plate. Use some trans fluid to lube the shaft and put it back in. Make sure you have the inner plate registered and tigthen the nut. Find a finish nail to use as you new pin - it will be shorter, so you need to bend it over on the back side a litte so it can't come out. Replace the roller arm and tighten it. Now lube the seal, slide it on the selector shaft (make sure you have it metal face out!) and then take the cup part of the infamous trans tool that isn't made right and tap the deal into the casing and drive it home. Put the linkage back, put on the trans filter and pan. Fill up your trans and cross your fingers. You may want to replace the Speedo seal while you are down there and the trans fluid is out, mine was leaking pretty bad too. That is much easier. than the selector shaft! Good luck." I guess this is what I'll have to do because I don't have access to one of the specialty tools. Maybe this will help anyone else trying to do this.
Also the yoke that could of used has a hole in it ,I think caddy did that for longtail .Im not sure ,Alot of guys weld them up,Maybe someone will chime in about the 400 yokes
Kelsey, the special tool is nice, but you can do it without it. Take a small screwdriver you are not to proud of (the cheaper the better, it needs to bend instead of break) and make you a little hook tool out of it, has to be ground pretty thin to work in between the shaft and hook under the seal, then pry it out. Use a suitable socket or something similar to tap the new one back it.
I think I got the new seal in and everything back together correctly. Here are a couple of pics. Anyone know if the end of the rod pictured just rests in between the two parts there (don't know any names of these parts)? One end hooks through the gear selector with the teeth on it and the other end seemed to just sit between these 2 parts. It didn't seem like it was "connected" to anything when I took it apart because it pretty much just fell out once I unhooked it from the gear selector. I still have to replace the tail shaft seal but I don't think that will be as much work.
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