TR3650 metallic bearing noise in 5th

Steve Mutter · September 25, 2010

The car is a 2003 mach 1 4.6 dohc. all gears are noise free till you get to 5th,you can feel it in the shifter and you hear a metallic bearing noise,you can put it in neutral and the noise will still their, but shift into 4th and it will go away. Does anyone have tips for me when I do the tear down?

mchan68 · September 25, 2010

Well, try to think of it logically. Since you mention the noise diminishes in 4th gear only, try to think of the operating condition that is present only in 4th gear, and not neutral or the rest of the gears. I believe 4th is the only operating condition in which the input and output shafts are locked together as a unit to provide a 1:1 ratio as opposed to turning at different speeds, therefore the surfaces of both shafts that contact each other (which I don't see a bearing between the two), are likely galled.

Steve Mutter · September 25, 2010

I looked at the disassembled view to see what is going on. I work on standard trans

Like once every 5 years so I always find it hard to get into. It's coming apart and I guess I will find what I find. I wish they had a power flow chart or something

Jim Warman · September 25, 2010

Steve... I'm old and that can leave me a tad addled. I'm thinking you have noise in neutral with the clutch engaged.... I'm thinking you have noise in 5th.... no noise in 4th.... no noise in 1st, 2nd, 3rd?

T45s is what I "usually" see for "baby coach manuals" but if you turn 'em downside up, they're all sisters. Having said that - does the noise change from accel/coast/decel?

The only "special" thing about 4th is that the pilot bearing 'twixt the input and output shafts is no longer a player. The cluster still turns but without thrust. In 1st, 2nd, 3rd and 5th - the cluster is under pressure (gee... they could make a song about that..) and, of course, a noisey bearing under pressure should be noisier.

Having the entrails of a manual trans laid out on the bench in front of you - hopefully you have a bench big enough to afford a meaningful arrangement - is what helps me...

Anyway... path of power... looking at the exploded view, I gotta say input shaft - main cluster shaft (and it is going to get tricky from here) - output shaft. If you aren't in 5th, the fifth speed cluster gear is free to spin on the cluster shaft. Shifting into 5th appears to lock the 5th speed cluster gear to the cluster shaft (Clear as mud, right?), in effect, taking one bearing out of the equation.

When regarding manual transmissions, it is important to think in terms of "speed" and "gear", terms that are sometimes used interchangably but shouldn't.

HTH