TH350 Won't engage park

[Honky Kong jr]

Glad to hear it's running good..

What did you have some one read it to you?????

 

[74 Shortbed]

What did you have some one read it to you?????

Smartass..

 

[da_raabi]

I pulled the pan and discovered that the parking pawl appears to be trying to engage the wrong gear in the transmission. The guide plate that aligns the pawl is forcing it to do this. Is it possible the previous rebuilder got the gears backwards inside the trans? Are there different guide plates available for the TH350?

Here is a diagram I put together using a pic I found online from a guy having the same issue. He never posted a solution though. I appear to have the same issue as my trans was identical to his. I added the text and arrows to demonstrate my issue:

You must be registered for see images attach

 

[74 Shortbed]

How about a pic of yours in that same area..

 

[da_raabi]

How about a pic of yours in that same area..

Unfortunately I did not take any pictures of mine, however mine is exactly identical to the pic I used in the diagram above. The owner of that pic appears to have had the same problem as I.

I can't seem to find a pic of this area from a properly functioning th350, or else I could use that for comparison.

 

[74 Shortbed]

Ok, let's see that pic without the text/drawings.

 

[da_raabi]

Here are two, both posted by the other guy on an automotive Q&A site:

You must be registered for see images attach

You must be registered for see images attach

 

[74 Shortbed]

Delete.

 

[crazy4offroad]

More than likely someone banged the trans into park while it was still rolling, and the lugs on the rear ring gear in the trans sheared off or rounded the "hook" on the parking pawl (since the parking pawl is the softer of the 2 metals). If you inspect it and it looks like it is not aligning with the ring gear lugs, more than likely a thrust washer or 3 are worn out causing the ring gear to ride too far forward or back.

You must be registered for see images attach

 

[da_raabi]

More than likely someone banged the trans into park while it was still rolling, and the lugs on the rear ring gear in the trans sheared off or rounded the "hook" on the parking pawl (since the parking pawl is the softer of the 2 metals). If you inspect it and it looks like it is not aligning with the ring gear lugs, more than likely a thrust washer or 3 are worn out causing the ring gear to ride too far forward or back.

You must be registered for see images attach

After inspecting the pawl (which looks slightly different from the one in the image above) and comparing to one I found on eBay, it would appear that it is in OK condition. I cannot verify if it is actually worn or not, but it looked OK to me.

By forcing the pawl to the rear, I can get it to engage the ring gear, telling me that it and the gear are likely not too badly worn. With a flashlight I could see the gear teeth looked ok as well.

Something else to note. When I pulled the pan, I found the magnet looked like this:

You must be registered for see images attach

Obviously something has worn quite badly in this transmission. Could this be the result of trashed thrust washers? Would there be any other indication of thrust washers being bad?

 

[crazy4offroad]

The metal on the magnet could just be shear material from the pawl. More than likely the trans could use a rebuild. The end play measurement would tell the tale. I don't have what normal spec and out of spec measurements would be in front of me but I'm going to guess it is out of spec if the ring gear lugs are too far rearward in the trans to engage the parking pawl. If you have it pulled you can push the input shaft as far into the case as it will go, clip a pair of vise grips to it as close to the case as you can get them, then pull the input shaft as far forward as it can go. Then use a feeler gauge between the grips and the case to get a good idea how much end play you have. I'm guessing likely more than 0.125 which is 1/8", about the thickness of the pawl.

Edit: 0.010 - 0.044 is factory spec, for performance use 0.010 - 0.020 is preferred.

 

[da_raabi]

Bugger. Trans is still in the car. Man this sucks. I literally JUST started getting the car back on the road. It's been going through a rebuild for the last 6 years!

The PO said the trans had been rebuilt not too long ago, and a sticker I found on the bellhousing seemed to corroborate that. I saw the engine it was behind and it was a pretty weak 305 or 350. Nothing special. Is it possible this was just a crappy rebuild?

Everything else about the trans seems to work correctly. Is there any way I can bandaid this for now? I don't have an ebrake of any kind so that's out the window. Any other ideas?

 

[Honky Kong jr]

Bugger. Trans is still in the car. Man this sucks. I literally JUST started getting the car back on the road. It's been going through a rebuild for the last 6 years!

The PO said the trans had been rebuilt not too long ago, and a sticker I found on the bellhousing seemed to corroborate that. I saw the engine it was behind and it was a pretty weak 305 or 350. Nothing special. Is it possible this was just a crappy rebuild?

Everything else about the trans seems to work correctly. Is there any way I can bandaid this for now? I don't have an ebrake of any kind so that's out the window. Any other ideas?

Does the E-brake work? If so keep it working and have some fun till you get a man trans in it a TH400 lol

 

[da_raabi]

Nope, no e-brake. The rear disc swap I did used calipers that did not have the e-brake ratchets. I planned to just put it in park then use those rubber wheel chocks from horror fraught if I had to park on a hill (rare... I live in FL. We dont have hills).

 

[da_raabi]

See now I'm gettin to thunkin. I can get the pawl to engage the gear and park the trans. I just have to do it by hand. The problem is that the bracket that "aligns" the pawl pushes the pawl forward, making it so that it cannot engage.

What if I just modified the alignment bracket? If there was some way I could shift the alignment notch (see pics above to see what I'm talking about) to the rear of the trans, I might be able to still get park to engage. At least enough for me to chock the wheels non-nascar style (envision my fat ass throwing the door open, running to the back wheel and trying to chock it while the car rolls away... yee haw!).

Thoughts on that?