Speedometer Gear - 09/02/2005

When I bought the car, the speedometer read 50% faster than it really was. This was funny, since it looked like I was doing 90MPH while pacing the traffic at 60. New gears are available from GM, but I had to find out what I had and where I was to know where I was going...

Floors look nice! Let's hear it for California cars again!

Steve inspects the transmission.

Steve inspects the rear while Dana looks on. The car has 3.23 gears (had to open the cover, no codes anywhere) and the fluid was in great shape.

The gears! I had a 36 turn driven gear (one of the smallest you can get) and a 21 turn drive gear. This comes out (with my tires) to a car with a 2.56 rear end (the transmission is dated 1977, probably out of a Grand Prix with cruiser gears). It's just a little off... Look! We didn't even need to use a new gasket since the old one was still in great shape! Cliff over at Walt-Bilt did a great job.

We pulled the drive gear off with a bearing puller (since we could find nothing else big enough to get over the output shaft). The factory service manual says to pull the gear off by removing the output shaft from the transmission. I say we veto that idea since it OBVIOUSLY is more work. The bearing puller worked just as well. Unfortunately we mashed the gear up pretty good, but that's okay since we aren't using it again. The GM 15 turn gear is what I ordered after doing some math and using TCI Automotive's web site. It cost $3.99, but took almost a 3 weeks to get here. Not many people do the speedometer gear conversion anymore apparently, since everyone in town wanted me to just use the reducer box: at $90 for the box and labor to install it? Hell no. Do it the right way I say. A 1.7" OD pipe was used to drive the new gear on. Big enough to clear the shaft, but small enough to not bugger up the teeth on the gear. Funny, we found the rusty old pipe in the bed of a truck at the back of Steve's lot. The guy was apparently going to toss it and Steve told him to save it, as you never know when you need good pipe. Like right now!

No leaks, no squeaks, no rattles. All is well. It drives down the road and whenever a police scanner on the side of the road shows my speed, it's within 1MPH of the speedometer. Who could ask for anything more? Total cost was $6 for the gear, $1.50 for the gasket I didn't use (Steve gets a free gasket!) and an afternoon of the car on the lift. Pretty nice compared to paying someone else to install a $90 reducer box.

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Last updated September 30th, 2005