Peterbuilt

Tuesdays job is to change the filter in my th400 transmission.
Haven't done this before and my question is does the "O" ring go on the filter first and then push it back into the transmission and put the bolts back in?

427Hotrod

The oring goes on the plastic tube between the filter and the trans case. Pull it out and replace the oring. If you have two orings...put them both on. Then stick filter on and install the retainer bolt. The bolt has a shoulder on it...so don't be surprised when the filter still moves around after you tighten it.

JIM

JimT

You may also want to replace the kickdown switch (détente relay). It is located at the bottom of the tranny, and can be purchased for around $20.
Good luck

doorgunner

Annnnnnnd.....if your car isn't "original".....buy an aftermarket transmission pan that has a "quick-drain-plug" welded into it...it makes draining the fluid much easier without the possibility of spilling.

Also......you can carefully "tap-down" the bulging area around each bolt hole (if needed) to prevent the pan from developing leaks at the gasket sealing area.

Jud Chapin

Very messy job. What I've found that works nicely is a large concrete mixing tub which you can buy at Home Depot for about $6. It's large enuf to catch all the drippings.

Peterbuilt

Hi Jim, thanks for the refresher. I owned this 74 for 15 years and it's been 14 years since the last filter change. I do kind of remember the filter floats in there even with the bolt being snug.

Peterbuilt

Overall that would be a smart thing to do, while I'm at it, but if the new kickdown switches are as bad as the new window switches then I'll wait until the old one fails.

Peterbuilt

That's good advise and I know what you mean about spilling a lot once the pan is loose.

Peterbuilt

Didn't have time to get to HD today so I'll try to use the round bucket that I use for oil changes, and yes I have speedy dry and plenty of rags.

Thanks again to all and Happy Holidays!
Pete.

427Hotrod

Leave the front bolts until last. Remove the others and let it tilt downward at the rear with front bolts still in place....then gradually loosen them until it is off.

JIM

atikovi

I'm changing the fluid and filter on a later model TH400 and before removing the filter bolt noticed I could move the filter up and down a good 1/2 inch or more. Is this normal? I was thinking someone installed a replacement bolt that is too long until finding the above quote in a search.

7T1vette

YES!!! The real "trick" is to get the pan down without drenching yourself with tranny oil. Other than that, changing the filter is no big deal. Buy a good quality filter kit at NAPA [not 'the Zone' ] and 2 gallons of ATF (synthetic if you want).

If you have a squeeze-type or crank-type siphon and tubing, put the tube down the dipstick filler hole and siphon out as much trans oil as you can. You can remove all the pan bolts if most of the oil is removed.

If you have no way to remove some of the sump oil, do it the old-fashioned-way. Remove all but the corner bolts on the tranny sump pan. Loosen corners a one end a bit, then take the other corner bolts out while you hold the pan up in place. As you lower that end of the pan, oil will POUR OUT EVERYWHERE. Have good sized drip pan under the trans if you want to stay dry.

Remove one bolt from the filter and pull the filter out. Make sure the rubber seal on the suction tube comes out with the filter.

Jebbysan

Once again Jim is reading my mind......been doing it this way for years.....be patient and let the fluid drain completely then keep loosening the last bolt....the pan will keep falling in the back.....when you have enough out.....grab it and take the bolt out.......dump the rest!

FYI.....during install.....I find using only a rubber trans pan gasket with no sealer is the best bet. Make sure the pan is flat around where each bolt tightens up....tap them flat if not. Use a 1/4 air ratchet with the air turned down to 40 psi to tighten them. This works perfect.....just tight enough and not overly so.

If you have the money of course I always recommend an aluminum pan.....has drain plug and easier to seal....as well as lowers trans temps.

Good luck,

Jebby

raydog9379

I'm about to tackle this one myself here w/ the TH350. Did it several years ago, and have a leaky gasket due to some stripped bolts (been dealing with the leaks for years and pretty tired of it now). Bought a helicoil kit and new trans pan. 2 reasons I bought a new pan. 1) Orig. one is more than likely warped and 2) prob. most important.. at some point I'm going to be doing this again and drain plug is going to be nice given my past experience. I could prob. hammer the orig. flat like others suggested but for the price I went with the new pan and drain hole option.

Key here is to torque to inch pounds. Some people torque to ft. lbs by mistake and that doesn't go well.

To the poster asking about the long bolt. Most likely they had a nut on the top because they stripped out the hole and used a long bolt/nut combo. I have one in mine that I know of, and at least one other jacked up hole as well that I'm going to try to fix here shortly w/ the Helicoil kit.

Big2Bird

cruban

Old thread revival. Just a quick tip as I did this just recently. I decided to swap out the pan for an aluminum one with a drain plug, thus the current pan was going in the trash anyway, so I drilled a hole in it and let it drain out, nice, clean and easy.

silver74vette

I use an oil extractor to pull all the oil from the pan before I remove it. Works great!

BlowAMouse

first time i did it i used a trash can lid to catch the fluid.

installed a new pan with fins and built in drain plug