[goofyfootrider63]

3 months ago my son bought a 72 fastback, 351C 4V carb VIN says it came with a FMX tranny but i think its been replaced with a C6, that was a project car in process. the former owner did alot of upgrades to the engine, under carriage, etc. but the thrill of owning a muscle car is starting to wane.

the edelbrock website was very helpful in in tuning the carb and what not but now we are having an issue with the transmission.

The former owner put a B&M shifter in it and everything seems to be connected but when the car is started and put into reverse/drive it doesn't seem to engage.

two questions:

Is the transmission tied in with the idle of the engine? Any ideas / help would be appreciated.

by looking at the tranny housing, can we tell if its the C6 or fmx tranny

[RemRem123]

You can tell by looking at the housing if it is a C6 or an FMX, the C6 is aluminun housing, so a magnet will not stick while an FMX is cast iron so a magnet will stick!
This came from another thread, courtesy of wilit!!
You can also look at the tranny pan. A C4's transmission pan looks like this:
http://www.charlietranny.com/C4.jpg

A C6's transmission pan looks like this:
http://www.charlietranny.com/C6.jpg

A FMX's transmission pan looks like this:
http://www.charlietranny.com/FMX.jpg

The transmission is not "tied into the idle" as far as I know, other than the fact that the faster the engine spins the gear in the tranny shifts!
Will it engage 2nd or 3rd? WHat if you manually put it in 1st, 2nd, etc??
Try searching this site, upper right search box, you'll probably find someone with the same problem

[Kebean]

This may be an obvious one, but the transmission is filled with fluid. ATF type F to be precise. If there is no fluid, or it is the worng kind, the gears won't engage. That said, I'm pretty sure you already checked that. Also the linkage is connected and not slipping right? And the vacuum modulator is hooked up.

When you ask about RPM, no it doesn't matter, but if your tranny is low on fluid sometimes when you rev it, it engages. Well, mine did... but it was an FMX.

=K=

[goofyfootrider63]

what about the torque converter being the problem?

[andrewmp6]

The idle will be off if theres any vacuum leaks and when you put the car in gear the idle will change too.