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How to find out of Tranny is TH350 or TH400 ?

Posted by amity (My Page) on
Mon, Mar 16, 09 at 18:56


I'm usuallly over on the decorating boards but I have a car question so what better place to ask. *smile*

Hubby came to his senses and realized we'd never be able to get his Dad's car back to pristine condition, especially with his job teetering right now.

I put an ad in local paper and instead of a price, I used the Best Offer method as I don't have a clue what the car would be worth.

Now I am getting phone calls asking if the Transmission is a TH350 or a TH400.

How do I find out this information?

The car was ordered in 1969 in Mpls. Mn.
1970 Buick Le Sabre 455 engine. All original miles, tranny, etc. But I have no way of knowing about the tranny size.
Any help you can give will be greatly appreciated.

Thank you!

Follow-Up Postings:

RE: How to find out of Tranny is TH350 or TH400 ?

If your transmission code is BC or BT it's a 400.
If it's BK it's a 350 or take it to a transmission place.
They will tell you in 5 seconds.

RE: How to find out of Tranny is TH350 or TH400 ?

IN 1970 the plant that I worked in we were building The A body cars. And every 455 engine had a TH-400 behind it. We called them M40's. M40 is the RPO code. If it had a TH-350 the code would be M38. If you could find RPO label it would have all the codes for your car. Eng code, trans code, paint code,etc.,etc.,etc.. Sometimes the RPO label is in the glove box. On the spare tire cover. On the spare tire support. For you particular car I am not sure where it is. It could be missing by now. Now that being said does your husband know anything about car? If so have him do this. On the passenger side of the car Look down where the dip stick tube goes into the trans. If there is a downshift cable going into the trans (we called it a detent cable) It is a TH-350. If not it is a TH-400. The TH400 has a single wire that plugs into the trans on the drivers side for the downshift. Another way to tell the difference is go to the passenger side and look under the car at the side of the trans. The TH400 will have a vacuum modulator in front of the dip stick tube. The TH-350 will have a vacuum modulator behind the dip stick tube towards the rear of the trans.

Well I am going to have to take a rest now. This put a strain on my brain. ;>) You know its been 39 years.


RE: How to find out of Tranny is TH350 or TH400 ?

Kalining and Bob_K,

What an encyclopedia of information....THANK YOUUUU!

Because of this info, I was able to gather up some of the old, yellowed, crackly papers and find that the transmission is a TH400.

Just to make double-sure, I had hubby check and there was no cable.

At least now I can answer those questions I'm getting about the tranny, and with my fingers crossed, this car won't have to turn into a very large Planter in my back yard but can be used by someone else for what it was intended.

Thank you SO Very Much!!
P.S. My hubby has great sentimental attachment to this car. It was the last car his father ordered/drove and son and Dad spend lots of quality time going places together in the last months of Dad's life.
At hubby's insistance, I'm the one doing all the research, etc. on this car so that's why I've not asked him or his friends any questions but instead came here....the less hubby is involved, the less it bothers him.
Here's some pics of the car in case you want to take a walk down memory lane. *smile*
Again, Thank youuuuu!

Here is a link that might be useful: Almost a Planter

RE: How to find out of Tranny is TH350 or TH400 ?

Easier way to tell still. The pan of a 350 is pretty much square with one corner cut off at an angle. The pan of a 400 is a bit more oblonged and the corners are rounded in. The 400 is the better tranny imo.

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