Some trouble with a 97

[TonyBuckets]

First off thanks in advanced for any help. I have a 97 two door Tahoe, 5.7 V8 vortec, stock transmission, the owner before me messed up the wiring with a hack job of a system. currently buying a new cluster and wiring harness for the dash.

so now the first problem I have is shifting into reverse the truck will idle backwards give it a little gas and its still fine, but if I'm backing up a slight incline or punch the gas I get this horrible noise like a clicking/grinding.

Second problem is driving on the highway sometimes i get an intermittent vibration sounds like it's coming from the rear end of the truck.

and a small one is the speedometer will die on me while driving, make a quick stop at 7-11 turn the truck on it works fine again for at least a couple of miles then dies again.

Again thanks to anyone willing to try and help me out with this, the truck is my daily driver and i can't afford to leave it at a shop while they try to trouble shoot it and fix it.

 

[SunlitComet]

scan for codes and make sure the tranny fuse is good first. Second inspect your drive-shaft for wiggling side to side. Third report back here with results. Any other anomalies and do you have pics of this wire carnage?

 

[TonyBuckets]

I'll take photos and post tomorrow of the dash. and thanks i'll get the codes and check the drive shaft. someone mentioned the parking pin slipping back in or something like that for the reverse problem

 

[TonyBuckets]

This is the wiring, i just found the switch for the rear wiper and put that in, the other two are just aftermarket toggle switches that don't do a damn thing.