I'm looking to put a low gearset A 999 in a Duster 360 project. I'm aware that these transmissions can be found in the M body Diplomat/Gran Fury cop cars as well as the Chrysler 5th Avenue models. The problem lies with telling the difference from a standard 904 with the 999. I like the idea of the lower ratios for improved performance, but if I stumble across a Diplomat that has had a standard 904 transplanted in, I'd have no way of knowing. Any suggestions?

part number stamped on hte pan rail is all I can think of

Many times the 70s cars are untouched and just worn out,I can say on the 76 up the second set of numbers on the ft bottom row will show D31 for a 904,D32 for a 998 and D33 for a 999. Then a D38 A HD 904.

Ive seen the trans outlast two timing chains and so more then not ive found the trans to be org, and then of course you can look at the trans numbers, but if it says D31 id pass as its probably the 904.

999 was developed for use behind the 360.

There has to be a 10 times greater number of 998s than 999s. Maybe you should look for one of those?
R.

They are lock up trannys. look for the input shaft being non splined for the first inch or so.

Also, a LU converter will have a flat ring in the front cover where teh lockup clutch rides, about 1" or so wide, nearer the OD. Not a guarantee for a LU trans, though (could be the wrong converter).

Is the only difference between a 998 and the 999 the 999's 5-disc front clutch?

The 999 was introduced in '74 but the low gearset didn't appear until '80 and not in all units. Look for an '82 or later.

As stated, the only way to know externally is by the P/N stamped in the pan rail.

My A999 was labeled on the bell housing.