'64 TH-400 slips in Park

[Guest]

I've got a '64 Riviera with the TH-400 tramsmission. It occasionally slips when in Park. That is, the car will roll backwards when parked on a hill. I know that there is a pawl that is supposed to lock the driveshaft in place. Preliminary analysis would indicate that the pawl is not engaging (or the shift linkage is misadjusted and it's actually in Reverse).

Before I pay someone large sums of money to gut the tranny, I'd like to get a grip on the problem. So:

- Has anyone else had this problem?

- What was the cause?

Thanks.

[NTX5467]

From the way it looks in my '68 Buick Service Manual, the parking linkage and such should be accessible with the transmission oil pan and maybe the trans filter removed. I suspect your '64 transmission would be similar.

There are several parts to the internal park linkage, so I would hope it would be an adjustment issue with the main shift linkage instead of a parts failure issue. Maybe one of the little spring clips failed or something easy? You can disconnect the linkage at the trans and operate it manually to see if there's any change.

It appears that the pawl engages a toothed ring on one of the clutch housings that is attached to the output shaft. Might even be a wear issue where the pawl and toothed ring interface? Probably just need to drop the pan, change the fluid and filter, and do some investigating.

Enjoy!

NTX5467