Is this a 700R4?

I think its classified as a 4L60...later became the 4L60E(E for electronic controled).

They didn't have 4L80E's in '91!

The 4spd Auto available in '91 on ALL trucks IS the TH700R4 which was also badged 4L60!

What is the shape of the trans pan?

Square = TH700R4

Square with 1 angled corner = TH350

Pan with a similar shape of Texas = TH400

Look at this link for exactly what they look like -

That would be my bet. My 91 3/4 ton suburban has a 350 and a 4L80E trans. It was the first year it was offered in heavy duty emissions, light duty trucks. So if you have 4 positions on the gear selector then it is a 4L80E is not then it is a TH400.

mark

'91 was the first year for the 4L80E

'93 was the first year for the 4L60E

-Bret

I just had a look at the pan, and the drawings on

do not match. I'll have another look at the casing for more markings. (It's on a bench right now) Or I could send a photo if anyone is interested. My email address looks like it is munged, but works the way it is.