Reminder to members, please access your profile and make sure that you have created a secret question and answer. This is required to enable the system to send you a Reset Password email if you forget your password.

Main Menu

67 deville transmission slipping?

Started by TomB, November 29, 2021, 06:20:10 PM

Previous topic - Next topic


Getting close to finishing building up a deville convertible out of dozens of crates of loose parts. Engine runs smoothly, but car rolls only at snailspeed. What might be the cause? not enough ATF, some adjustment in the linkage or the lower steering column required? What am I overlooking? Couldn't find guidance in the shop manual. Thanks,


It takes 3 gallons of ATF to fill your TH400 trans, it will not work
much on less.  Also make sure the filter is not plugged, that
cartridge type is harder to find.  I use that vintage trans but
convert them to a 68 up filter, available everywhere. 

There is is no linkage that will stop the trans, short of not putting
it into a forward gear.  An original needs a total refresh, all rubber
seals inside and out, though the hard parts could be just fine and
I would re use them.  The factory manual is full of info to do this.
good luck, Bruce Roe

Dave Shepherd


Got it, extra fluid and had it run for more than 10 minutes, slowly picked up traction. It was slipping in all gears, including reverse.

Dave Shepherd

Ok, so it is full on the dipstick, not overful?