hotbrakesracing

here is what i have--4 speed(m-22) and 4:56 gears and 255-60-15 tires rear tires. the speedometer is off big time. according to my gps 80 mph is 55 mph and just gets worse the faster i go. i have tried the red 21 tooth and the blue 20 tooth plastic gears..anybody know the correct driven gear i should use??? :cool: but :confused:

Glensgages

No....
but last year, I had my 2.87s swapped for 3.73s, and my buddy who performed the swap bought a GM-Part# "speedo-recalibration" piece (really, I think it was a gear-reduction set-up) for $50 (?) that installed INTO the 2.87:1 speedo gear.
I think he said they are made for just-such 'outrageous' gear changes, and GM might have one for YOUR set-up, too!
A word of caution: this 'reducer' is a few inches wide, and it 'bound' the speedo cable, shearing the square hole in the OEM gear-shaft into a ROUND hole...TWICE!!!
I eventually had the replace the driven OEM gear, AND the drive-gear, INSIDE the 700-R4, for the correct calibration.
If your speedo cable is on much of a bind now, it'll only get worse with the reducer 'sticking-out' a few more inches...
Good luck!!!

norvalwilhelm

You won't find a gear low enough. I had to get a gear reducer from the local 4x4 shop. They guys are always going to the really big tires and to get the speedometer correct they buy these little gear reducers. In our case we want to do the opposite so you just take the gear reducer apart, reverse the gears so it slows down the speedometer instead of speeding it up. Our local 4 x 4 wrecker has boxes of them and only charges $5 each. They have a number stamped on the outside say 30% etc.
They fit perfectly on our cables, They can be hooked either directly to the transmission or in the center of our 2 peice speedometer cable.
It will get you close and you can fine tune with gears.
Those 456 gears are rear

Racer16k

I used a GM speedo gear reduction box. I got the part number from someone on the forum. It was a factory piece for Chevelle with 4.11 gears, or something like that. I can't remember what the gear was in the trans. I'll look, maybe I can find the part number.

Here it is! http://members.core.com/~faldrich/speedo.htm


[Modified by Racer16k, 7:13 PM 4/4/2004]

hotbrakesracing

thank you guys..i now have a place to start solving this :cool: