irkennedy

When I bought my cutlass the 400 trans had a plug where the speedometer cable goes so I do not how fast I'm going. Has anyone dealt with this before? Is there a way to remove it?

don71

If it has a plug in it, chances are the transmission came from a big car, like an Olds 98. Those cars had the speedo driven off the front wheel. Probably a long tail transmission as well.

Any chance you have a pic? Just in case something else is going on here. Might not hurt to give us the total length of this trans, for comparison.

I'm not sure what direction to point you too. You might be out of luck.

hookem horns

In the meantime, get the Speed Box app for your phone - simple, accurate and FREE. I got it to check the speedo accuracy of the Cutlass and the boat. If you have a tach in the car, use the app to check your speed at various RPM's once in top gear (2500 = 60mph, etc).

joe_padavano

More specifically, the 1965-70 Delta 88 and Ninety Eight drove the speedo cable from the left front wheel, not the trans. Your transmission is from one of those cars. Some of these transmissions came with a plug in the hole, some simply didn't have the hole machined. If yours has the plug, it is possible to remove it and install the speedo gear holder so you can run a cable. You'll also need to pull the tailhousing and install a drive gear on the output shaft. If your case isn't machined for the hole, you are S.O.L.

JohnnyBs68S

Anyone know why Olds did that? Seems to be a more complicated way of getting road speed to the dashboard (the cable would have to flex U/D/L/R w/ the spindle, no?). I always thought this was wierd on my buddy's dad's '70 98, when he told me the speedo pickup was on the front wheel, I didn't believe him until he punched it and spun the rear tires and the speedo hardly moved. Seems that the only benefit would be that you could switch tire size or rear gear ratios without having to re-gear the speedo cable, yet these cars weren't exactly ripe candidates for doing that.

irkennedy

So if it is not drilled for it then I would need a new transmission? Is there any other way to determine mph without a new trans?

joe_padavano

Well, a new case at a minimum.

From Post # 3 above:

4speed455

I was told if the tranny doesn't have the provision for the speedo, the drive shaft of the tranny will not be machined to accept the speedo drive gear.

joe_padavano

The long tail output shafts are the same. The drive gear just wasn't pressed into place.