Transmission whine

[jaredts]

'83 Silverado, th350 (some p.o. swapped in).  Just took a 30 mile trip, and when I got off the interstate there was a loud whine sound in drive or reverse but quiet in park and neutral.  I pulled to a gas station and had my wife hold the brake in drive.  It definitely sounded like it was coming from the torque converter or that area (no inspection cover--its on my list).  The fluid was full, nice and red with no burnt smell.  The transmission was shifting perfectly with no slip.  Everywhere at low speeds it was whining really loud, but I can't hear anything above 20 mph or so.  I drove several miles back to the interstate and then 30 miles home.  From the interstate to my house the sound was gone.  Ideas?

[bake74]

      The front transmission pump, and not the torque converter or roller bearings, may also be the whining culprit, and require a simple replacement.
      Sometimes it is hard to tell between the torque converter and front transmission pump, did you check to make sure your transmission was full of fluid ?
 

[bd]

I'm initially inclined toward a converter issue, although a restricted filter can cause a nearly identical whine and should be checked/replaced if the pan is removed.

A worn/faulty pump, typically, will make noise whenever the engine is running, because it spins constantly, regardless of whether the transmission is in gear, park or neutral. 

However, with regard to a torque converter, when the transmission is 'in gear,' the engine is running, and the vehicle isn't moving, clutches are applied and the converter turbine is held stationary by the drivetrain as the converter housing (the impeller) spins around it (remember, the converter housing bolts solidly to the flexplate & crankshaft).  The resulting differential rotation inside the converter, between the impeller and turbine, works the converter internal bearing - it sings.  But, when in 'park' or 'neutral' the whine disappears (or at least diminishes), because clutches aren't applied, so the impeller and turbine spin together, as a unit.  Additionally, converter whine traditionally decreases as vehicle speed increases (or TCC locks up), because the impeller and turbine are coupled (diminishing toward no differential rotation).

Still, before tearing anything apart, make sure the noise isn't telescoping in from the engine....

[jaredts]

Fluid level and color was good.  Would a plugged filter also cause slipping?  I didn't have any slipping.  I may be wrong but when I shut the engine off during the second or so that the engine came to a stop I think I heard what sounded like a bad bearing--a little bit of a growl.  This is the first time I have had any of these symptoms, but it has been a few months since I drove it more than 15 or 20 miles at a time.  I have never changed the fluid or filter.  I'm not sure if I should drive it a little more to try and nail down the symptoms, just change the fluid and filter, or just change the converter, fluid and filter.  At around $100, a converter isn't terribly expensive.  If its going bad I assume that driving it is filling my transmission with debris.

[bd]

I don't think the filter is your problem.  At this point I'd check the converter bolts and flexplate.  Before draining the transmission, I'd verify fluid pressures, then drain it and evaluate any debris in the pan.  Look for steel (magnetic), aluminum, brass, brown flakes (clutch material), black granules (rubber) and hard parts.  If you find a bunch of crud in the pan, leave it in the pan undisturbed and take the pan to a transmission shop for an opinion.  These initial checks might dictate the repair strategy. 

But, I suspect you're going to end up replacing the converter, and depending on how it looks, possibly the pump, flush the cooler, and replace the filter.

[VileZambonie]

I didn't see if you mentioned aeration of the fluid. Any bubbles present on the dipstick? Aeration is typically caused by overfull fluid level, overheating of the transmission fluid etc. You're sure it's not coming from the power steering pump or any other area correct? This is a TH350 not a TH350C correct?

[jaredts]

TH350, not TH350C.  No obvious aeration.  Fluid was normal--full, not aerated.  Checking converter bolts is on my list when I get to it.  I've had a busy weekend and I'm not sure when I'll get to it.  When I stuck my head under the truck it sure seemed to be coming from the converter, I don't think its power steering or anything outside of that area.  Not the best time of year for me to work on this since I don't have a garage, but I'll check some things out soon.  Thanks for the advice so far.

[VileZambonie]

You should start by changing the fluid and filter.

[jaredts]

I changed the fluid and filter today.  I get the feeling it had been done not too long ago.  There was very little fine powdery sludge like I've seen on other high mileage fluid changes I've done.  There was, however, a significant amount of steel shavings.  After the change I haven't driven it, but once again have the loud whine and a little bit of a grinding sound in anything but park and neutral.  I have a feeling that just changing the torque converter and flushing the fluid would be a risky move.  Any advice?

[VileZambonie]

It's not the converter. Pull the unit if you want to salvage it or beat it til it blows up and secure yourself a 700R4 to take it's place.

[bd]

It's not the converter. Pull the unit if you want to salvage it or beat it til it blows up and secure yourself a 700R4 to take it's place.

X2

[jaredts]

I've been perfectly happy with the th350, but a 700r4 would be nice.  Is there a difference in difficulty or cost in rebuilding between the two?  What tools are required?  For someone who hasn't rebuilt a transmission is it worth it?  I'm not sure if I want to take a chance on a used transmission or not.

[VileZambonie]

You're better off having a reputable rebuilder handle it and for yourself practice on the old 350 if you want a guineau pig to learn on.