hey guys i just recently completed my lg4 to speed density 350 tpi swap and as im dealing with the usual hickups of a motor swap i pulled the car out for a test drive last week and about 3hrs later im cruising back towards home and my speedo just dropped to zero and hasnt worked since.i also have a gm tech 1 scan tool and it wasnt reading any anything also at this point.now i do have a 87 transam with the 4 out buffer box and i had to wire up the 730ecm to this for speedo signal aswell as 2 wires down to the vss sensor at the tranny.all the wires look to be in perfect condition and same for my soldered connections.should i take them all off and see if my stock speedo works again..if it doesnt work does that mean i fried my buffer box?any help would be appreciated.

 

The speed density '730 ecm has its own built in buffer box. You can feed the VSS Signal right into it and it has outputs for speedometer and cruise control.

 

mine did the same thing but every once and awile it wiggles up a bit or pegs to the 110 mark. MATTODOOM are you saying there is a way to fix it?

 

ok i just want to clarify this before i wire it wrong.i have a yellow and purple..i think it might be purple/white wires that im suppose wire to vss and on the vss sensor i think the wire colors when i looked earlier were black and pink.do i just tap into those for signal? and the red/white wire from ecm goes to cruise control which im not using,and the red wire that is marked speedo is suppose to go to my guage in the cluster and not to the speedo wire coming out of the buffer box?basicaly i bypass the buffer box all together.i originally had the speedo wire hooked up to the speedo wire at the buffer box think that it needed to read speedo signal..not send one out.could i have fried the buffer box which made my speedo gauge stop working?

 

well i disconnected all the wires i had going to the buffer box and rechecked continuity and power and ground and everything there is reading fine.im not sure how to check if my vss sensor is sending signal out though.any ideas guys?