converted 69 cutlass from 2sp to th350 and have found a leak that is coming from where speedo cable screws into trans speedo gear housing. it is not coming from housing, but from where speedo gear shaft comes out of housing and engages inner speedo cable. i looked in 69 assembly manual and they show an "adapter" between housing and cable, but when i look at conversion chart for speedo gears, they list that some ratios do not require an adapter. is the adapter required or is there a gasket i'm missing in the speedo cable?
also speedo is off 10mph (over real speed) and trans guy who rebuilt said close as i'm going to get it. 3:42 "O" 12 bolt w/ 15" rim 26" tire. any ideas?
thanks

 

My gears and tires are not factory original. I used the factory chart to get a ratio between driven gear and drive gear based on the gear and tire in the chart. I than ratio'd that to my wheel and rear gear to help me get to a drive and driven gear combo. I have 3.90 gears and 245-15 tires and was able to get almost the exact combo of drive and driven gear WITHOUT using the adapater. You might need to change your housing on your transmission depending which driven gear you use.

IIRC there is an two orings on the housing. One around the outer diameter and another in where the cable connects.

Do you have a factory service manual?

 

http://speedometersolutions.com/ http://www.transmissioncenter.net/sp...n_______va.htm One of these should be able to help you out as far as getting the right speeo gear, probably have the O rings also.

 

That is a nice chart on the transmissioncenter link. Would have saved me a lot of math.

 

The adapter does not seal the housing. As noted, there are two O-ring seals. It sounds like the inner one is bad on your cable adapter. Remove the cable adapter from the trans and pull out the speedo driven gear. Look inside the adapter and you should see the O-ring.

 

not sure if understand correct. i do not have the adapter (did not come w/ rebuilt trans - do i need one?) I just screwed speedo cable into trans speedo housing. I know there is an o-ring for the housing to trans seal, but the other o ring for the gear is also on the inside? just want to make sure before i tear it apart.
thanks
also, what is purpose of the adapter?

 

Correct. Since the adapter does not seal the speedo gear housing, the fact that you don't have one has nothing to do with your leak. Adding one will also not fix your leak

Correct. The smaller O-ring is on the inside diameter of the speedo gear housing. It seals to the shaft of the speedo gear.


Some combinations of rear axle gear and tire diameter were not able to be accommodated by the standard set of speedo drive and driven gears. In those cases, an adapter with an additional gear ratio inside it was used to bring the speedo into calibration. In some cases, a right angle adapter as needed for clearance.