I crawled up under the Hudson to hook up my speedo. Only to find that this TH400 never had a provision for one. I am told it was run off the front wheel when it was in a Olds. My question is has anyone here run into this and figured a way to get the speedo to work without tearing the trans apart?
Yep... run into this. No easy fix. That speedo hole is precision machined and you would play hell trying to machine it even if you stripped the case. Find another case with the hole and swap your guts over is the easiest way. I just did this for a guy last winter on his TH400.
Yes its in the case. I was wondering if I could use a tailshaft that has the provisions for a speedo with a reluctor ring such as VSS. I have an Electric speedo from Classic Instruments.
if you have an electronic speedo you might be able to use an old driveshaft magnet sensor for a cruise control
Sorry... I missed it where you said you were using an electric speedo? Being on a traditional hot rod website I "assummed" you were trying to hook up a cable speedo. (my bad) That changes stuff. Maybe find a different tail housing and look at it to see if you can use a reluctor and speed sensor from a 4L80E. Mock it up and see if you can machine the tail housing to fit the sensor. It may even be able to go where the original gear went on the main case. Being an electrical sensor vs a mechanical gear, you could probably get away with drilling it yourself. Probably could be done. Depends on how bad you want it.
btw this is what I'm talking about http://www.summitracing.com/parts/RPC-250-4165/ The normal short tail 400 has a tailhousing shorter than any 4L80E
The olds was not electronic, it just had the drive built into the front spindle. It can actually be adapted to any number of cars with a little work.
last time i looked there is a "boss" where the speedo bung would be. looks like you just tap on the thin aluminum filler, and pop it out and its there. never looked inside if the output shaft has the "threads" for a big speedo gear. it uses the large cover. might have to tap the hole for the small bolt, but the hole is there