Firewall knock

[Surfdougyfresh]

Hey everyone. I have an issue with a fairly loud knock, against what sounds like the firewall, when I'm shifting from 1-2 and 2-3. I'll be in first, get up to 3000rpm, drop the clutch, let off the gas, shift, and when I'm letting off the clutch and giving some gas, there's a single knock against what sounds like the firewall. It's almost as though there's a 16mm nut hanging from a string somewhere and in the same way that your passengers head will bob when shifting, the nut swings against the firewall. The 2-3 shift isn't as loud, but still there. It will also happen if I brake or let off the gas suddenly too. Can anyone think of something that might need to be adjusted or tightened up to eliminate this knock? I've been up under the console and in the back of the engine bay looking and shaking everything....Thanks!

[Guest lothar34]

Remind us all what car you drive.

[Yukonart]

Could be a bad/broken tranny mount. Between shifts, the engine will rock a bit until it engages with the transmission again under load. . . . if there's a bad mount, it'd probably knock during this movement.

[Setright]

Agreed. Transmission mount, or maybe an engine mount. Lift the car up, and examine the mounts. With age they get softer and allow more movement.

[sea#3]

Check the "dog bone " that goes from the firewall to the top of the trany

Bet ya the bolts are loose

 

SEA#3

[Surfdougyfresh]

Yes, I suppose I should tell you that I drive a '98 outback, 2.5L. I just replaced the tranny mount and both shifter bushings. I had to wonder what would cause both shifter bushings to fail and settled on the tranny mount. I'll take a look at everyone's suggestions. Thanks.