Hello all!! Bonneville strange noise in fourth gear

Hello to all. I've lurked around this site for some time and have found the information here extremely useful.

I've got a problem I just can't figure out. It's a 98 Bonneville SE, AT, 80K. I bought this car this past January and it is in very good condition.

Here's the problem. In fourth gear, I'm hearing a whirring or whining noise when going 50-60 Mph. The noise is only audible when I very lightly press on the accelerator. It seems to get louder or higher in pitch with engine speed. If I release the accelerator, it stops. The noise coming from somewhere in the front end. Over 60 Mph, it stops or is barely there. If I accelerate hard, it isn't as loud.

No codes present or pending. I did have a code P0742 (TCC stuck on) about a month ago. It was the hottest day of the year so far. I let the car cool down and drove it later. It was fine. I did get the EPC, TCC PWM, 1-2, 3-4 solenoids, but haven't put them in yet.

I've done some routine maintenance since buying the car. Drivebelt, plugs and wires, upgrade to Dexron VI, Dorman upper intake manifold, changed left half shaft that had a blown boot, new alternator bearings, new tires. Basically, just things that should be serviced or may present problems later.

I was a heavy collision tech for over 30 years and have had to diagnose some rather odd drivetrain noises, but this one has me guessing.

Thanks in advance for any replies or suggestions.

Almost impossibe to hear/ diagnose this from here, agreed? If the noise can be duplicated in neutral at a given rpm, then it is usually engine related. Based on your description sounds like a drivetrain noise. Could be the trans final drive?

Almost impossibe to hear/ diagnose this from here, agreed? If the noise can be duplicated in neutral at a given rpm, then it is usually engine related. Based on your description sounds like a drivetrain noise. Could be the trans final drive?

Thanks for the reply max. Agreed it's impossible to diagnose from here. I have watched the tach to see exactly what RPM this occurs at. It's about 2500 RPM. I have tried to duplicate it in neutral with no success.

I have tried to put it in 3rd and take it up to 2500 rpm to see if it is rpm related. It's not. It is speed related. I tried 3rd gear and 50-60 mph and I don't hear it. It has to be in fourth(OD).

My thought was that it could be the transaxle output bearing(s). If that were the case, I would think it would get worse at higher speeds. But it stops being noticeable over 60. At 70, it's fine, or at least sounds fine. Additionally, if were a bearing, I would have heard it when I did the third gear 55 mph test too. As I said before, it has to be in fourth gear.

It seems the worst when cruising at 55 MPH and just barely touching the throttle. Just a low howling noise. Foot off the gas and it's gone. I can make it come and go. I guess I'm hoping someone has heard the same thing from their H body. I've done a search on the AF and have seen many howling threads, but none that have solved it.

When I first got the car, I don't recall hearing it. The weather was much cooler then. It happened soon after I had a new set of Bridgestone tires put on. The weather was also much warmer then too.

I'm stumped by this one.

It does sound like something in the final drive just like a noisey rwd diff, or pinion bearing would do.

Not sure about that... It is common of the 97-02 4T65E Transmissions to eat the 4th input Hub shaft and strip the splines, this trash in the trans at times will take out the torque converter in due time...

Hard to say, but this does not sound like a Trans bearing, Doesn't sound like a wheel hub assembly either, but not out of the realm of possibilities...

Not sure about that... It is common of the 97-02 4T65E Transmissions to eat the 4th input Hub shaft and strip the splines, this trash in the trans at times will take out the torque converter in due time...

Hard to say, but this does not sound like a Trans bearing, Doesn't sound like a wheel hub assembly either, but not out of the realm of possibilities...

Hi Jrs and thanks for the reply. Not the hub/bearings. When I first started hearing it, I read what others had said about getting 80-90K out of the factory hubs. I was planning a trip and was concerned, so I changed the the fronts.

Also did a pan drop and changed trans filter. Added 9 qrts Dexron VI. Before starting, took off the upper trans cooler line on the radiator (output) and replaced it with a fitting with clear plastic line to a marked bucket. Took three people to do. One started it. The next watched the bucket while I added more fluid. Once he saw clean fluid coming out, the engine was stopped. I topped off the fluid level, then made sure the fluid from the pan drop and what was pumped out was equal to max fluid capacity, 13 quarts. I'm pretty sure I'm running 90% or better Dexron VI.

Also, pan had nothing unusual in it.

Drove the car today, using only third gear. Ran great and no howl all the way up to 75 mph. Didn't try D(rive). So that kind of rules out the trans output bearings.

I know the 4T65E are infamous for the Pressure Control Solenoids going bad in addition to 4th input shaft. I'm going to change all solenoids in the valve body next week and see if that helps.

Any other thoughts are very welcome.

Once again, thanks to all that replied.

Pulled the side cover today and replaced the EPC, TCC PWM, 1-2 and 3-4 solenoids.

PROBLEM FIXED!! Howl/whine is gone. May just have to have a beer or two to celebrate.

Job went pretty much as expected, about 6.5 hours (with many breaks due to the heat). Biggest problem was getting the sub frame low enough to allow the side cover to come off.

Would I do it again if needed? Yeah, only because I'm really cheap.