Hum-Whirr

[Endeka]

Hi there,

I recently bought a 1998 C5 Coupe. The car has 81,000 miles on the original engine, and was well kept (climate-controlled garage, no rust or inordinate wear). It has a new clutch (<800 miles), upgraded big break/rotor kit, and is running Firestone Firehawk runflats (just in case any of that is relevant). It is a 6-Speed MT. It passed PA state safety/emissions with no problems at all just a few weeks ago. I live right across the border from Trenton, NJ in PA.

I noticed a few days ago that it is beginning to produce a hum-whirr type noise which is noticeable, but not overwhelming, only in sixth gear and only around 55-65MPH. When I go beyond that speed, it stops. When I go below that speed, it stops. When I take my foot of the accelerator, it stops instantly, and when I put it back on, it begins again instantly (at that speed).

I was referred to a mechanic who worked on Corvettes for a now defunct GM dealership in the area, and started his own shop when they closed. He has only done my inspection so far, so I can't really comment on how good he is yet. However, when I called him on the phone, he told me pretty frankly, sight unseen, that some bearing (I did my best to write it down, but now I can't seem to find it) was "brinelling" in the transmission, that there was no point in changing the fluids because it wouldn't help (the people on the Corvette forum said to do this before I dive into anything more expensive), and then offered to get me the price to replace the transmission-around $2,000 with labor, fluid, and parts.

Needless to say, I'm a little surprised by that; the repair is 15% of what I just paid for the car. If it really needs it, I'll do it, but I wanted to get a second opinion first, especially since his diagnosis seemed so rapid, and he wasn't willing to entertain any of the mitigating options others suggested (maybe they're being naive? I don't know.)

What I want to know is:

1. Was my mechanic right? Is there nothing for it but a new transmission?

2. If he is right, is there any harm in driving the transmission into the ground? I can live with the noise, and I'd like to get at least a month or two worth of use out of it before my first multi-thousand dollar repair, but only if the case is hopeless, and only if doing so won't hurt anything else on the car.

[c4c5specialist]

Hi there,

First, does the noise occur in 5TH gear at the exact same speed????

Second, draining the fluid into a magnetic tray would help to determine if a bearing is going bad. The fragments, with a full failure of a bearing, will show up on the magnet.

If it only happens in 6, then I am looking at the transmission. Also, usage of a listening device would also be recommended to determine actual source of noise.

The key is that the driveline of the c5 Corvette MAGNIFIES the noises in the driveline.

Allthebest,c4c5