Doing a rebuild on a 97-03 model 4R70W, during teardown it became apparent that the Ring Gear attached to the output shaft, had some unusual wear.
4 teeth on the outside of the ring gear, look like they had been shaved down, all other teeth looked perfect.
Some minor scratching around the inside of the case around the gear, nothing major. No loose chunks or metal, No bearing or snap ring failure…
Any Ideas?
Assuming the transmission is otherwise in good, functional condition, seems like the sort of damage you’d expect in a car used for drag racing. Any history like that?
Sort of related recent Car Talk puzzler, Mazda sedan’s timing belt’s teeth kept getting sheared off for no apparent reason. Each time after belt replacement engine ran fine in shop, idling, and when bumping rpm. After 3rd or 4th replacement job, shop tech decided to remove valve cover, noticed one of the cylinder head bolts had broken in half. Top half just sitting in the hole on top of bottom half, not connected to anything. When car idling, no problem. But when driven over a bump, head bolt would jump up and interfere with a cam lobe.
It’s a major accomplishment for a diy’er to even attempt to rebuild an automatic trans. Are you a diy’er?
What does the park pawl contact in that transmission?
Agree. Attached to the output shaft, that’s probably where the parking pawl engages. That’s what happens when you put the transmission in park with the car still moving.
I thought an automatic trans parking pawl usually engages on the output shaft directly, fits to a notched gear gadget on the output shaft. I have to admit I know less about this subject than almost anybody, but I’d be surprised to learn the parking pawl engages with a planetary ring gear.
Or a repo truck grabs it by the front wheels and pulls it out of a driveway and drags it down the road till safely able to pick up by the rear wheels and the dragging sheared the ring gear some…
It usually does. That looks like the “notched gear gadget” you’re speaking of. It may be a hub for a set of clutches, hard to tell from that picture, but if it’s a hub the clutches don’t generally do that to the hub. They can do that to EVERY tooth on the hub if the hub is soft and the engagement is harsh, but not usually to just a few teeth.
Another vote to look at the parking pawl, even though I would have thought more than 4 teeth would be damaged.
Please do reply with what you find.
The parking pawl engages only one tooth. If the car is moving and you put the transmission into park the pawl will try to engage, scar the gear as it moves past the pawl, and the try again at the next tooth as you jam the shift lever into the park position. Eventually it engages the gear, but the scarred teeth are what happens as the pawl cannot engage fully while the teeth are moving.
What’s not known on that transmission is if the parking pawl drops in from the top or if it slides in from the side.
If it drops in from the top, how would that explain the damage to only the outer edge of the teeth.
I’m assuming if a driver shifts a car into park while it’s not stopped completely, they would do it more than once over 26 years. Which doesn’t explain why only 4 teeth are damaged.
I still think it’s parking pawl related, but with only that one picture, it’s hard to be conclusive.
Yes Sir I am a DIY’er! Only about 20 now, but I grew up wrenching on old tractors and farm equipment, and I got a love for the work! Just about the only 2 things I’ve never done are full Trans and Engine rebuilds lol
I bought the truck cheap on Facebook Marketplace with the intent to challenge myself and fix it all running for my own little farm truck! Not a whole lot of history to go on…
Thank you so much to everyone that took time to help me out! It’s my first transmission rebuild, and I love that I’m able to keep learning more as I go!
The parking pawl is set at the back of the case from the valve body side, and you can see the little notch in the back of the inner case, right where the ring gear sits!
