1956 Buick Speedometer Gear

[Beemon]

How many speedometer gears were there for the Dynaflow? I'm thinking only two, but there's an option to put larger tires on the Specials. The reason I ask is because I've finally tracked down a good rear end for my Buick. It's a 3.23 instead of the 3.36. All the local yards have specials, and the 3.36 cars I have found won't part them out. I'm very particular about my gauges working as intended and I only plan on pulling the rear end once.

 

Pics of the diff:

In comparison to what I had:

 

Thanks guys

[Ttotired]

If you cant find gears, you can do a speed test (say 20,30 and40mph) and compare that to a gps speed, then take your info and speedo to a gauge repairer to re calibrate it

 

Might save you lots of frustration

 

 

[Beemon]

I have access to a Special Dynaflow, it's been my donor car for several parts. I was just curious about how many gears there were since it was an option for Specials to have oversized tires and there's no mention of gears in the shop manual.

 

I didn't think about recalibrating the speedo, though! Maybe take the gauge cluster out of that car and have it calibrated, Thanks!

 

Found it in the shop manual (Syncromesh section); Specials with 7.60-15 tires would have a #18 gear, where 7.10-15 tires would have the #19 that is the same in the 7.60-15 cars with the 3.36 gears (what I have). Was the upgrade from 7.10 to 7.60 tires common?

Edited October 28, 2016 by Beemon
Found it (see edit history)

[old-tank]

You need a 56 parts manual which will detail the usage of all the available gears...look under group 4.337.

The 19 tooth gear used on my 55 Century with either 3.41 or 3.36 rear gears and 7.60-15 tires was dead accurate.  When I went to the comparable radial size 225-75R15 the odometer was reading 4% more miles than actually traveled (compared to GPS).  Changing to a 20 tooth gear the odometer is again accurate.  The 20 tooth gear was specified for the 55 Special with 3.6 rear gears AND 7.60-15 optional tires.

Guessing now:  if using  7.60-15 tires with the 3.23 gears an 18 tooth gear would be needed; but if using radial size 225-75R15, then the 19 tooth would probably work.  Get out the GPS.

(There were no 3.23 rear gears in 55; changing to radials effectively changed my rear gear ratio from 3.36 to 3.6.)

Willie

[Guest]

http://www.bobsspeedometer.com/1/120/index.asp

http://www.clarkbrothers.net/ratio_adapters.html

http://www.texasindustrialelectric.com/800_Series_Speedometer_Adapter.asp

http://www.yotatech.com/f116/mechanical-speedo-correction-box-install-pics-195986/

[old-tank]

I looked into the ratio adapters, but with one attached to the transmission there is no room on a 55 to connect the speedometer cable....X-frame is in the way.  No room on a 55 at the speedometer either..maybe on a 56?

[Beemon]

It's pretty tight on a 56, too.

 

Willie, I hadn't thought about the difference between 7.60-15 and 225/75R15. Right now I've been driving with a cheap set of 235/70R15 so I've been naive to the point regardless. By what you've said, I might be able to get away with the stock 19 gear. 

 

Thanks for the tip!

[Guest]

I have seen an adapter made so that you used a short cable to go from the tranny to the adapter and then a cable from the adapter to the speedo.  One I saw was mounted on the frame and one was under the instrument panel.  As they are all custom made I don't think there is any reason that they have to mount on the transmission.

Edited October 29, 2016 by Guest (see edit history)