I bought 86 5.0 recently. And it didn't take long before the trans went out. which i figured was gonna happen the guy i got it from was building the engine and rear end and neglecting the trans. Anyway i got a WC t5 from the local salvage yard and nothing is different except the speedo gear. The one that came out of the car was a whine color speedo gear and the one that came with the new trans is black. Now for the weird part. 0-30 my speedo is accurate after that it slowly slows down at 45 I'm doing 55 at 55 I'm doing 68. the guy at the salvage yard said the trans was for an 86 gt so i don't know where to start trying to get the speedo to read right. the rear gear is a 3.73 thanks for any advice