Performance Q&A Questions - Performance Q&A

Kevin McClelland Feb 1, 2009 0 Comment(s)

Speedo Me Up
I have a typical stupid question about the speedo gears in my tranny. I had to put a tranny in my '85 Z-28, so I used what I had lying around, a 4L60 out of a '93 Caprice. The problem now is that the speedo reads about 72 mph at 1,800 rpm. What gear do I need to get things right? My current combo is a 3.27:1 rear gear. The tranny tailshaft drive gear is yellow, and the speedo-driven gear is white and has 36 teeth. My rear tires are 245/50R16s. Any help would be greatly appreciated.Aaron SalernoVia email

A Speedo questions aren't stupid after you get a nice little invitation to the courthouse from your local law enforcement agency. Whenever you swap in a new transmission, you should try to steal the speedometer drive and driven gears from the original. You said you have a yellow drive gear on the output shaft. GM never had a yellow drive gear! Your '93 Caprice trans should have had a gray 15-tooth gear if it's from a passenger car or a blue 18-tooth gear if from a wagon. To correct your speedo calibration, you'll need a 38-tooth driven gear (PN 1359272) for the gray drive gear or a 45-tooth driven gear (PN 9775187) for the blue drive gear. Your driven gear sleeve will work with the 38-tooth driven gear, but if you need to go to the 45-tooth gear, you will have to swap out to a PN 25512339 to hold the larger gear.

As always, we couldn't answer any of our readers' speedo questions without the help of Ken Casey at Burt Chevy. For years I've recommended that readers bring their speedo questions to Ken. He has sold more speedo components than any other dealer in the nation. Check with him to keep the flow of gears and sleeves going. I've threatened that it will be engraved on his headstone that he was the Speedo King.


Groan No More
My '96 Impala has 260,000 miles on the clock and has never been wrecked, but it started to make growling sounds when I turned the wheel. I had the service shop replace both the pump and box with Auto Zone parts, and after the makeover the car turned hard to the right and really easily to the left. The shop then installed a remanufactured GM part, including new hoses and a belt. After all that, I'm still having the problem. Fortunately, I kept the original box and want to know where I can send it to get tested. What do you suggest? Is there any difference between the Impala boxes and others? What about a speed-sensitive ratio? Thanks!
Cliff Blacke
Via email

Boy, that's a pile of parts with the same results! We assume that the problem you're talking about is the odd power-assist. Yes, there are many differences in the boxes. There are high-effort, low-effort, and speed-sensitive ratio boxes that change the ratio with vehicle speed. Finally, the internal stops differ greatly among A-, F-, G-, and B-bodies. You're on the right track having your original box rebuilt and set for your driving preferences. Lee Manufacturing in Sun Valley, California, is the source you're looking for. At Lee, they build many Sprint Cup boxes and also boxes for many circle racers around the country, and they have the ability to custom-tune the power steering box right to your driving style. I've even had them revalve a power rack from a late-model VW bug, which is a long story for another day. Give them a call and get your original box in the mail.

Lee Mfg.


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