Transmission Noise

[ASJT3]

Hey guys,

Ever since I purchased my use '90 C1500, there has been this loud ball-bearing type noise coming from under the car. Since the truck was pretty rusty, I assumed the noise was coming from the rear drums sticking (also the car felt like something was holding it back).

After servicing the drums to find out everything is fine, I find out that the noise is actually coming from the trans.

Here are the symptoms:

1) Loud ball bearing-type noise that increases with speed (almost sounds like a water pump bearing that has worn out)

2) Drag at high speeds (truck doesn't coast well/loses speed)

Any ideas what the isue could be?

thanks ,

alex


EDiT: should be noted that I changed the trans fluid/ filter to no avail, also seems to shift fine, if a slight bit hard

[Schurkey]

Originally Posted by ASJT3

I find out that the noise is actually coming from the trans.

Here are the symptoms:

1) Loud ball bearing-type noise that increases with speed (almost sounds like a water pump bearing that has worn out)

Consider also checking the U-joints on the driveshaft; and the pinion bearing (is the pinion loose in the housing?) in the rear axle. Sounds can travel up 'n' down the driveshaft and appear to be coming from somewhere else.

Originally Posted by ASJT3

2) Drag at high speeds (truck doesn't coast well/loses speed)

COUNT the shifts from a dead stop with the lever in OD, and accelerating very gently. 1>2, 2>3, 3>4 + torque converter clutch (TCC)--four "bumps" where the RPM drops, although the TCC "bump" may be very mild. First Guess: You aren't in overdrive. Verify by driving at steady 50+ mph and moving lever to "3" and hearing the engine RPM go up. Verify TCC by driving steady 50+ mph, and lightly touch the brake pedal with left foot while holding gas pedal STEADY (not hard enough to apply the brakes, but hard enough to activate the brake light switch) TCC should disengage briefly, RPM goes up.

Originally Posted by ASJT3

EDiT: should be noted that I changed the trans fluid/ filter to no avail,

What color was the fluid, and how much/what kind of debris was in the pan?

Originally Posted by ASJT3

also seems to shift fine, if a slight bit hard

That might contra-indicate not having OD. Is the throttle valve (TV) cable adjusted properly? LOTS and LOTS of TV cable and/or TV valve problems with those transmissions.

[ASJT3]

Thanks for the reply! My trans doesn't have overdrive, I think its a Turbo 400 3-speed.

When I changed the trans fluid, it was reddish brownish, very blood-like and not translucent at all. There wasn't a ton of debris, just the usual fine black metal powder, no big pieces or shavings. The rear diff fluid when I changed it yesterday was dark black and disgusting.

[j cAT]

Originally Posted by ASJT3

Thanks for the reply! My trans doesn't have overdrive, I think its a Turbo 400 3-speed.

When I changed the trans fluid, it was reddish brownish, very blood-like and not translucent at all. There wasn't a ton of debris, just the usual fine black metal powder, no big pieces or shavings. The rear diff fluid when I changed it yesterday was dark black and disgusting.

the transmission tail shaft bushing may be worn ..when checking the driveshafts/U joints with wheels off the ground rotate the drive shafts and check for wear ..the 400 3speed transmission is a very strong performer.

[ASJT3]

Originally Posted by j cAT

the transmission tail shaft bushing may be worn ..when checking the driveshafts/U joints with wheels off the ground rotate the drive shafts and check for wear ..the 400 3speed transmission is a very strong performer.

Thanks for the advice, I'm thinking this problem is probably a combo of the bushing and worn U-joints (read somewhere that vibration during accel/decel, which i have, may be cause by worn u-joints).

I'll go ahead and check on her and let you guys know!

[Schurkey]

Originally Posted by ASJT3

Thanks for the reply! My trans doesn't have overdrive, I think its a Turbo 400 3-speed.

I think it's unlikely that a C1500 would have a TH400; but what do I know? I'd love to see a photo of the pan. Does the dash indicator have an OD position?

Originally Posted by ASJT3

The rear diff fluid when I changed it yesterday was dark black and disgusting.

Yup. That's the way axle grease is. Smells terrible, too...right?

[jdmccright]

If you have a two-piece driveshaft (for extended cabs and/or long bed), the center support bearing could be bad. It sounds exactly as you describe, coming from under the floor. A competent place can replace it for ~$125. It has to be pressed on and off.

[ASJT3]

Well I guess technically the tranny is a 3L80? It's got no overdrive (no dash indicator OD). It is a long bed standard cab, is there a way I can tell if it's two piece? It has a composite sheath along the length of the shaft.

[jdmccright]

You'll see a u-joint somewhere around where the bed begins and a half-circle shaped rubber isolator next to it. The carrier bearing is inside the rubber. It may be possible to remove the two bolts holding the bearing to the crossmember and push it up high enough to clear the crossmember so you can spin test it...the driveshaft yoke will slide out of the transmission tail to accommodate this.

If the bearing sounds like an old roller skate, it's bad. It should be quiet and have no play whatsoever.

[ASJT3]

Originally Posted by jdmccright

You'll see a u-joint somewhere around where the bed begins and a half-circle shaped rubber isolator next to it. The carrier bearing is inside the rubber. It may be possible to remove the two bolts holding the bearing to the crossmember and push it up high enough to clear the crossmember so you can spin test it...the driveshaft yoke will slide out of the transmission tail to accommodate this.

If the bearing sounds like an old roller skate, it's bad. It should be quiet and have no play whatsoever.

Thanks I'll test this, it definitely sounds like an old roller skate (a LOUD old rollerskate) while driving.

So what is the exact name of this part that I would need to replace?
Thanks,

Alex

[jdmccright]

It's called the carrier bearing or center support bearing. You can buy it separate of the rubber, but it's usually more cost effective to buy it and the isolator together. Considering the age of the truck, the rubber is likely to be old and soft anyways.

If you remove the shaft to have it replaced, mark the crossbeam so you can center the bearing assembly to realign the shaft when you install it.

[ASJT3]

Just checked and its a 1-piece driveshaft, no carrier bearing. The transmission tailshaft is about 8" long though, my money is on the tailshaft bushing that j_cat mentioned, what do you think?

[jdmccright]

That or the u-joints. Raise the rear wheels and spin the driveshaft while your underneath the truck. You should be able to hear where the sound is coming from.

[ASJT3]

Finally got the chance to change out the u-joints. The rear one was fine, the front was worn and had some brinelling on two of the posts. Unfortunately the sound hasn't gone away! I'm going to try and raise the rear again to pinpoint this noise. BTW I noticed something strange when I took off the driveshaft. The transmission spline shaft was wobbly. Is it supposed to be like that or is that a major problem?

Thanks,

alex

[j cAT]

Originally Posted by ASJT3

Finally got the chance to change out the u-joints. The rear one was fine, the front was worn and had some brinelling on two of the posts. Unfortunately the sound hasn't gone away! I'm going to try and raise the rear again to pinpoint this noise. BTW I noticed something strange when I took off the driveshaft. The transmission spline shaft was wobbly. Is it supposed to be like that or is that a major problem?

Thanks,

alex

read posting #4 again !