Quote:
Originally Posted by benzdude42
i'll be taking my engine and transmission out in about 6 weeks to fix my rear main and was hoping to take this opportunity to work out my transmission conflict. before i owned my 85 300d cal. someone replaced the motor and transmission with that of a 84 300sd leaving me with no way to count miles or tell how fast i was going. i have the old 722.416 that shifted fine 7 years ago but spent at least 3 out side in the elements on its oil pan like it was dropped from the car. is it possible that its worth putting back in? or does anyone know a way to hook the 722.303 to a electric speedo and tac?
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I'm confused by what you're trying to do...
You have an '85 300D chassis which would have come with the mechanical speedometer.
In that car, you have an '84 300SD engine/transmission which would have come with an electronic speedometer.
You rightly point out that reinstalling the original 722.4x transmission would restore speedometer operation. (And I actually think that despite sitting out for a few years would not be problem, provided the torque convertor was fully seated and the dipstick was fully seated.)
So if your question is "how can you replace the speedometer head with one from an SD so it will work with the currently installed 722.3?" I'm not sure if that's possible. I think the heads are different, unlike other components like tach, oil pressure, fuel gauge, coolant temp, clock etc, which can be easily swapped from cluster to cluster.
Now if your question is "how can you replace the tailcone on the 722.3x transmission to go from electronic to mechanical?", that is theoretically possible, but in practice I don't think it will work. You can physically swap the tailcones (in fact I did this on my 617 -> 107 swap to convert from mechanical to electronic) The problem is that the mechanical tailcones have an oil squirter to lubricate the speedometer gear and I just don't know if the two are interchangable going that direction. (Stretch might know - he seems to be the tranny specialist around here)
On the tach side, your 85 gets its tach signal from the EGR controller (believe it or not) based on a signal that comes from the bellhousing (a VR sensor reads the flywheel teeth and feeds that A/C signal to the EGR controller) so you're kind of out of luck, unless you want to go to all the trouble to get an '85 intermediate plate and swap that in. Since you're working on the rear seal, this might be an option. Otherwise, you'll need to get a tach amp and install that along with the appropriate wiring AND swap in a tach module from any vehicle that uses the tach amp setup. (The tach amp gets its signal from a VR sensor and a tooth on the harmonic balancer.)
Go spend a couple hours at the junk yard looking at the various speedometer modules and see if you can find one that would fit (or could be modified to fit) your cluster.
If you can find an electronic module you can get it to work with most any transmission by using an externally mounted VR sensor and modifying the driveshaft to serve as a trigger wheel. (Here's a link to a pretty comprehensive discussion -
http://www.peachparts.com/shopforum/diesel-discussion/312801-mechanical-electronic-speedometer-conversion.html
Good luck