Buzzing when under a load???

I have a 95 mustang GT that was converted (by a previous owner) from an automatic to a manual. The tranny, a Tremec 3550, was rebuilt last year. Also installed was a new transmission mount, the clutch and short-throw shifter.

The problem is that under load (above 2800 rpm), there is a buzzing/grind noise that seems to be coming for the Bellhousing area. Sort of like something is binding or rubbing under torque. The noise stops when I release the throttle. Could this be caused by worn pilot or throw out bearings? Or is could it be a flywheel that needs resurfacing or maybe the misalignment of the drivetrain? What could be causing this problem?

Wow! It's good to know that I'm not alone with this problem.

Honestly, I'm at my wits end on this one. I taken to couple of drivetrain guys. Both says it's the transmission's design and nothing can be done to fix it. I'll have to live with it or replace it. However, neither is sure what is actual problem is. Maybe I should poll other 3550 owners and see if they are having similar issues.

For the last year, I have driven mine about 150 miles daily of mostly highway travel. Like yours, it does not appear to be a serious mechanical issue. It just sounds horrible.

I don't have the money or desire to 'kill a flea with a cannon". So, before I buy a new tranny, I'll do more research.

Let's keep each other posted it we make any new discoveries. Good luck!

Thanks 88Stangboy for the info. At least I can worry less about it breaking.

I did get an email today that told me that I should pull the tranny and check the shims. Now, the guy who rebuilt it last year told me that he packed it as tight as possible.

Is it possible to pack it 'too tight'? Would that cause that 'buzzing sound'

No_Rice,
do you think that your shims could be packed tight?

Thanks for the all the info. I going to try the 3/8 space on the driveshaft and the washer under the tail of tranny. I think I already have a nylon washer in shifter but I'll check that also.

I made a few more calls and one guy thought that it could be the input shaft. Sounds pricey and I'm sure that it would really solve the problem.

Also, did a few experiments during my morning commute and I noticed a few things.

1. There is a change in resonance if I hold the shifter.

2. If I run 70 mph and shift to neutral, the noise is totally eliminated. (which was expected)

3. Just like it happens with yours, my tranny at 2800 rpm in 4th and let it wind down by itself, the chatter is present.

4. If I run 70 mph in 5th, horrible noise, shift down to 4th gear, the noise virtually goes away.

I am not clear on what this is telling me but I it leads me to believe that something is mis-balanced.

The spacer did the trick! No more problems at 70 & above. Still having the noises as I slow down from 50 mph in 4th. But I really think that this is a design issue.