When I got my firebird on the road last year the needle broke off my speedometer. I didn't want to go though the hassle of sending in my old one and I liked the idea of having a speedo that read 0 miles since it was a fresh restoration. I ordered a new speedo from Ames and installed it. When I went to drive it the speedo was off 15 miles an hour. I put in different gears to try to correct this issue. I used all gears for the 2 speed that is in my bird but no luck. As of right now my speedo is off 10 mph.
My thought right now is that I have to remove tail housing and install a different one to correct this issue? I got one off a 400 Pontiac thinking that it was the same but it is not(to short).
Does anyone have any thoughts regarding this?? My bird is 68 with 2 speed.
Here is a site that will help you. I purchased the adapter to correct my speedo. With the adaptor you'll need to know the percentage that your speedo is off, they have some in stock and can custom make them as well.
I have one of those adapters as well due to my 2.56 rear end. Even the 17 tooth tranny insert would not correct the low reading rally set. They adaptors work great.
It depends on your real speed vs your speedo shown speed to calculate the %reduction or increase needed.
My bird has 2.78 gears in it. I put aftermarket 17 inch rims on it. The weird thing is, when I took it out for the first time (speedo was working) the speedo was right on. When I put the new speedo in the speed was off. I tried all 4 gears that would fit the 2 speed tranny but it's still off 8-10 mph.
I had a similar problem with my speedo. I bought a used original off ebay for 20 bucks, cleaned it, rolled it back to zero miles, due to my resto, and installed. Works great, looks original, and now have 1200 miles since resto. Just cannot beat original equipment.....Just my opinion.
