TH400 strange park pawl issue.

[Anchor-Enthusiast]

Hello again fellas.

Tore into the TH400 on this '89 K3500 and have come across an odd issue.

Everything is very clean and looks brand new basically. The park pawl and bracket look perfect, the return spring is springing. And the rooster moves through the gears freely and with little effort. But the park pawl will not engage. The pin and housing are just fine, cotter pin still on the pin, I can push the pawl into position manually but as soon as I release it the spring pulls it right back out. The only issue I have come across is the rod/linkage that goes between the park pawl assembly and the rooster, it has a significant amount of up and down play. Is it possible that the rooster backed off and is out of alignment? I can't find any other issue.

It seems like the rod starts to push against the pawl assembly but doesn't have enough force to overcome the spring tension on the pawl.

And help would be greatly appreciated.

-J

 

[Anchor-Enthusiast]

And is this bracket facing the right way or do I need to flip it?

 

[Anchor-Enthusiast]

Problem identified. The steel plunger piece that interfaces with the park pawl was broken in half. Pictures attached. Never seen this before.

 

[NickTransmissions]

I've seen that once in this vintage of transmission (TH350) where the mechanism split just like the above pic. Its somewhat common with later six speeds, esp earlier units (common in this context is relative - its still an extraordinary rare event). The rivet at the end fails and parking pawl actuator falls apart.

Glad you caught it before a serious accident occurred (im assuming no accidents/mishaps)...

 

[Anchor-Enthusiast]

I've seen that once in this vintage of transmission (TH350) where the mechanism split just like the above pic. Its somewhat common with later six speeds, esp earlier units (common in this context is relative - its still an extraordinary rare event). The rivet at the end fails and parking pawl actuator falls apart.

Glad you caught it before a serious accident occurred (im assuming no accidents/mishaps)...

Well if nothing else this was good for documentation purposes for when someone else inevitably comes across this issue hahaha. And very interesting I gotta dig around in this pan and see if I can find that broken rivet.

And yeah all is well, nothing catastrophic happened the truck simply wouldn't lock up in park. Very thankful none of those pieces found their way into a moving component while driving.

Thanks for the additional info.

-J

 

[Wolvrine82]

Thanks for posting what you found. I have the TH400 in my truck as well so it is nice information to be aware of.

 

[evilunclegrimace]

Am I the only one that wants to know what a "rooster" is?

 

[DerekTheGreat]

Am I the only one that wants to know what a "rooster" is?

All I know is that they might come to s-nuff it.

 

[Anchor-Enthusiast]

Am I the only one that wants to know what a "rooster" is?

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It's called a rooster or "comb" it's the internal gear selector. They coined it a "rooster" because when it's flipped upside-down it resembles the head of a rooster. Link attached.

 

[Anchor-Enthusiast]

All I know is that they might come to s-nuff it.

well played hahaha