Trans shudder

ford

#1

Driving an 02 Taurus, 3.0 motor. Trans was rebuilt recently. Car seems to drive smoothly, with 1 driver. But on a road with dips, the trans seems to hum while car is down in dip. Hum lasts for 1-2 seconds. Back on level road, car is quiet. Only had car for a few weeks. I noticed hum within 1 day of driving. Tires? Wheel bearing? So, last weekend I had 3 passengers. Tried to accelerate up on ramp and the “hum” was very noticeable while accelerating. Any light cruising, the car seems quiet. I am leaning towards binding cv axles? Or bad valve body. Or something internal in trans. Gonna talk to former owner who paid for trans work.


#2

“Hum” and “shudder” are two different things in my mind. “Hum” is a sound, “shudder” is a vibration you can feel.

If you feel a shudder while loading the engine at 45 mph or above, I would suspect a torque converter clutch slipping. A used van I bought had a bad case of TCC shudder that was solved simply by changing the fluid, which had been neglected.

If it’s a humming sound but not a vibration you can feel, it doesn’t sound like a TCC problem.


#3

It’s not really possible to diagnose this via the internet. But one idea is that this can be normal after rebuilding a transmission and will eventually go away. Depends on what needed to be replaced during the rebuild. Sometimes new gears are required, and the new gears don’t quite mesh perfectly. If you’ve ever replaced the chain on your bicycle, you have probably experienced the problem of new-chain induced chain-slip. The pitch of the new chain doesn’t quite match the pitch of the sprockets, which over time wore as the old chain stretched.


#4

Car feels smooth at almost all times. Good moderate acceleration. No missing or stumbles. Cruise at 50mph and it feels fine. Hit a little dip in road and I definitely feel a rumble/vibration in drivetrain. From outer wheel area, not so much from trans/motor. As soon as I am back too smooth level road, vibration is gone. When I had car loaded with 3 passengers, all was good till I hit the on ramp. Than major rumble while I was accelerating. Once I let off gas and cruised , all was quiet. I only got car last week so I have zero miles on it. Motor/trans mounts?


#5

Drivetrain rumble/vibration under load at 50 mph sure sounds like torque converter clutch (TCC) slippage to me.

The TCC usually doesn’t lock up until 45+ mph or so. If the rumble/vibe does happen below 45 mph or so, it might not be the TCC. But if the rumble/vibe happens only at 45+ mph, that’s a pretty good indication it’s the TCC.

Since you just bought the car, have the transmission fluid and filter changed. The previous owner may not have done that in a long time. Just changing the fluid can sometimes fix even a bad case of TCC shudder.

And if the fluid change doesn’t help, you can buy an additive called ShudderFixx.


#6

I got car for basically nothing. So I had no concerns with issues. It looks good, so I got it. Sort of a gift horse. The major drivetrain rumble with passengers really threw me for a loop? It was like WTH? I did put a hitch on it so I was under car. Exhaust looks good. No broken hangers.


#7

Great. It was basically free. So spend $100 on transmission fluid and filter, and a tube of shudderfixx if necessary.


#8

Not to discount the good ideas posted above, but here’s another idea if they don’t work. When the transmission was rebuilt, the drive shafts had to be disconnected from the transmission. The FSM for my Corolla anyway recommends to put witness marks on the two parts where they connect, before disconnecting them, so you can put them back on w/ the same orientation. There’s often rubber vibration dampers on the front wheel axels, so it’s also possible one of those got lost or moved from its original position in the process.

I’ve never experienced a shudder problem myself re-installing front wheel drive axels on with a different orientation than they started with, but I have w/my 4WD Ford truck. I had a noticeable shudder on it after removing the main (rear) drive shaft to replace a U-joint. I hadn’t used the witness mark trick, so I had to just try some other combinations until I found one where the vibration disappeared. Seems like it would be a big time consuming job of trial and error, but removing and reinstalling the driveshaft on an older Ford 4WD truck is pretty simple.