4L80e grinding when manually shifting down to 3rd

horn12007 · March 26, 2020

Trans grinding issue.

Anyway, if you are driving the truck with the trans in drive, then shift it down into 3rd, it grinds....the noise reminds me of when you accidentally try to start a vehicle when it's already running and the starter hits the flywheel. No, it isn't the starter. This ONLY happens when shifting from D to 3rd. No matter on the speed. If I go from D to 2nd, it does not do that. If I shift up through the gears, it is fine. The truck shifts through the gears fine. It only grinds when shifting from drive to 3rd manually.

Thinking it could be a cable adjustment, but seems odd that it only happens in that situation.

Anyone deal with this? Doesn't seem common.

CamGTP · March 26, 2020

So if you are not moving and you slap it down into Drive, then go down into 3rd it grinds or it has to be moving?

Sounds internal to me if it does this while moving. Maybe something to do with the overdrive roller clutch and the overrun clutches on the planetary gear. I say that because I know for sure that on a 4L80e that in D4 only the roller clutch is engaged but when you pull it down into D3 the overrun clutches engage along with the roller clutch.

Have you pulled the dipstick to see how the fluid is??

horn12007 · March 26, 2020

11 hours ago, CamGTP said:

So if you are not moving and you slap it down into Drive, then go down into 3rd it grinds or it has to be moving?

Sounds internal to me if it does this while moving. Maybe something to do with the overdrive roller clutch and the overrun clutches on the planetary gear. I say that because I know for sure that on a 4L80e that in D4 only the roller clutch is engaged but when you pull it down into D3 the overrun clutches engage along with the roller clutch.

Have you pulled the dipstick to see how the fluid is??

I don't think the truck has to be moving. I haven't even checked the fluid. May be low or bad. But this doesn't seem to be a symptom of low fluid but never know. I just got it on trade and it's at my storage unit so I haven't done a compete inspection. It just seems like some type of engagement issue. If you never dropped it down to 3rd, you wouldn't even know.

I was thinking about having my gf hold the brake while I shift the truck into gear with a wrench and seeing if a little pressure on it either way stops the grinding. Heck, you could go D, 2, then 3 and it would be fine.