Replacing Transmission Fluid In A TH350

When I first purchased the car, the previous owner told me that it was hard to shift into gear because there was most likely a loose bolt inside the transmission.  So this project is about dropping the transmission pan and changing the filter, gasket, and transmission fluid.  Unfortunately, or fortunately, no loose components were found inside the transmission.  Everything looked good except the fluid which was a nasty brown color.  Hopefully this did not indicate a more serious issue inside the transmission.  I’m pretty sure it’s ok because I did not see a lot of metal flakes or metallic debris in the pan or fluid.

The things that you will need to perform the transmission service on a TH350 transmission is as follows:

Transmission service kit

Transmission Fluid, I used approximately 10 quarts to get to the fill line.  From research I did online I was expecting 6 Quarts, but the transmission may have been low on fluid, I did not check.

 

Fluid container, preferable with a wide mouth catch.

A funnel

½ inch socket with and extension to make it easy.

Once all the items have been acquired, you are ready to get to work.  This is a messy job, no matter how careful you are with dropping the pan you will get transmission fluid all over the place.  The way I did it, I believe it to be the least messy way, was to loosen the bolts towards the back of the vehicle first.  This allowed the fluid to drain out the back and into my fluid container.  I angled the pan towards the back as I loosened the rest of the bolts holding the transmission pan on.  Once no more fluid was draining from the pan using this method it was time to drop it.  Remember, the pan is still full of fluid and you want to catch as much of it as possible!

I removed most of the bolts, but left the ones in the corners attached.  This kept the pan up, with the fluid, while I devised my next plan.  I slid underneath the car, held the pan with one hand, and removed the bolts with the other.  I am not a magician so I spilled some but was able to lower the pan onto the ground without the fluid spilling all over the place.  That is the recommended method and it keeps most of the fluid in the pan.

Pan removed and on the ground

Pan removed and on the ground.

The filter was next to be replaced, it was held in place with 2 flat screws.  Just unscrew them and replace the filter.  Don’t forget to put the supplied filter gasket in when you change out the filter!  I know from experience!

This is the old filter

This is the old filter

Transmission With Filter Removed

Transmission With Filter Removed

New Filter

New Filter

Then I cleaned out the transmission pan.  Pay attention to what the fluid looks like and if there is any metal flakes or other debris in the fluid.  The fluid in this transmission was really dirty, pretty much like it hasn’t been changed in the 38 years it’s been in existence.  Other than that it looked ok, just brown and dirty.  So I cleaned the pan and got it ready for reassembly.

Squeaky Clean!

Squeaky Clean!

I put the transmission pan gasket on the pan and held it in place with bolts at the appropriate corners to keep the gasket from curling up.  Once in place, you can put the pan back up and start the bolts that you already had in the pan for the gasket.  Then you can put the other bolts in and tighten them up.  I went corner to corner like when you put on a tire so that the pan got snug up to the transmission nice and evenly.

New Gasket on the pan

New Gasket on the pan

Now it was time to fill the transmission back up with fluid.  From some of the research I did online, I started with 5 quarts of transmission fluid and started the car.  I let the car warm up to operating temperature and checked the fluid.  To my surprise, there was none on the stick!  I then poured in my extra quart that I had and I still had nothing.  I was a little concerned so I shut the car off and checked for leaks, there were none.  I went back to the auto parts store and purchased another 5 quarts of transmission fluid.  I started the car back up and started filling.  It took most of the 5 quarts before I got a reading on the stick!  Now it is full and looking clean!

Use a funnel to fill the transmission with fluid

Use a funnel to fill the transmission with fluid

Unfortunately this did not resolve the trouble shifting issue, I think the problem is just the linkage and it may just need to be adjusted.  I have not really had an issue with it since doing the service so I’m not that concerned, but the picture below shows what I think the issue is.  That spring loaded bolt is a little crooked and may just need to be lubricated a little better.  The linkage and associated parts in the transmission are designed to move a little so a little lubrication may go a long way.  Like I said, I haven’t had any issue with it so I’m not that concerned.

This is the part that i think will need to be lubricated

This is the part that i think will need to be lubricated

I took this opportunity to fix the exhaust as well.  The car was extremely loud when I first got it and has been ever since.  While doing the transmission service, I noticed that the header to back piper connection was very loose on the driver’s side.  I adjusted the muffler in the back to match the passenger side and tightened the whole thing up.  The next time I started it, the car was much quieter and purring like a kitten……at idle.  Once you give it gas and come to a stop the car dies.  I think it’s the fuel pump.  I ordered one, should be in shortly.

The Far side exhaust connection was extremely loose

The Far side exhaust connection was extremely loose

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