I am very happy with my replacement transmission but in the process something happened that causes occasional vibration of the dash... noticeable at lower speeds and lower rpm. I have no doubt it was caused by something when I installed the transmission but can't figure out what to even look for.

Any experience with this or good ideas on what would cause the issue?

 

Check to see if you have the insulation under the shift boot that fits around the shift lever.

 

What clutch are you using?

 

Same FW and PP I have had for years (toda / ClutchMasters) I just sand them off and put a new OEM FD and TO in when I changed the tran (and probably didn't need to order them, the old ones looked great).

Yes, I replaced the insulation but the vibration is really behind the dash and does not seem to be in the tunnel or near the shifter.

I am wondering if I could have got the lower header mount on with tension or something like that.

 

Just an update to say I figured it out... I may be slow but I am persistent.

Knowing that 99% of the time problems are caused by what you just worked on I spent a month triple checking every fastener and doing everything but dropping the trans again. Got an alignment and used an inspection camera to look at all the hidden places something might touch.

Finally concluded it had to be the tires (and they were needed) so I got a new set today and sure enough the vibration is gone.

So the conclusion is that coincidences may be rare but they do happen...