Okay so when my taco is cold and i get it up to 50 or so i get an aweful loud buzzing noise from behind the dash. Loud I mean real loud. when I slow down it goes away and comes back when i speed back up. eventually goes away when the truck gets up to temp. Any Ideas?

 

Sounds like the speedometer cable may need grease inside the sleeve.
Or just replace the whole thing.
Edit: good way to test that, disconnect the speedometer cable from the transfercase. If the noise goes away then you've found the culprit.

 

Thanks Scuba, I dont think that its the spedo cable the noise is a constant pitch and does not go up or down with the speed. And it is just all of the sudden deffening and then drops to barely noticeable when i slow it down. but its one extreme or the other, and only when its cold. I appreciate the quick respose and will give it a try anyway.

 

Well that was my only guess. It'll take you only a few mins to get the cable disconnected from the transfercase and then only a few seconds of driving to know if that's the problem. Worth a shot. I think it may leak oil out of the hole when you drive with the cable disco'd so plug it up with something, even if it's just duct tape.

 

I have one of those noises that comes up when it's below zero, and I hit the freeway. It sounds like a bad bearing on a fan being moved by the speed of the wind... after a few minutes, it goes away.

 

yeah mine does the same thing. its in the speedo for sure, i even put a brand new cable in and all that did was smooth out the noise, its still there. I wonder if getting a brand new speedo thingy for the back of the gauge cluster would do it (toyota makes you buy the entire cluster) or if this is just an issue they have for the early tacos with the cable driven speedo?