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Ford 4600SU Tach

B

BlackTransAm

New User
I was investigating the non-working tach on the ford
4600SU I was given a while back, and found that the cable
was not connected anywhere on the motor. While searching
for the tach drive, I found that it has none. The tractor has
an alternator, but I have no idea if that is factory. In place of
the tach drive there is a plug with a recessed hex drive.
Messicks parts catalog shows the tach only going to the oil
pump drive. Would this tractor originally have had a
generator with the tach drive, or am I missing something
here?
 
Going acording to the 4000 tac drove off the back end of the generator and getting rid of the generator got rid of the tack connection. I have heard there is an alternator made with the tack drive and very expencive and I have no idea where to get one. The 4600 is newer than what I had with 2 4000 and a 5000.
 
Tractor came from the factory with the oil pump tach drive. If you have a threaded plug in that area, I suspect the original block was replaced at some point in the past with an older block. Reply back with the casting numbers and we can confirm. Look for a number that looks something like this: xxNN-6015-x.
 
That would be a late 1960s block. The C7NN means the original casting was designed in 1967. Since the 4600 didn't come out until 1975, it means your block is not original to the tractor.
 
I assume i would need to get the generator for a 4000 to have a tach then? Seems odd to do a block swap on a tractor like this, but i have no idea of its history.
 

The conversion alternator normally found is a Delco 10SI with internal regulator
Your 4600 should have a Motorola alternator with a external regulator, there forth modifications would need to be done to the wiring harness to have a proper charging system
Also you would have to install a older -000 series dash as those models and the conversion alternator drive the tach in the opposite direction
Converting to the older model generator would require changing tachs, regulators and it would be easier to swap in a 4000 wiring harness
I ve never heard or know if it s possible to make a threaded insert to screw into the block and allow the oil pump tach drive adapter to fit
Unfortunately your in a bit of a pickle with not simple fix and the best fix is a newer engine block
 

The original generator w/tach drive on it that needed the voltage regulator which would have come on that engine was Not the most reliable. Nor did it have a very high output. I'd guess most of them have been changed to an alternator by now - with or without a tach drive.
Remember too that on the pre 1976 Fords with generator the tach turned one way and the 76 and newer Fords the tach turned the opposite way.
So even if you get a working tach drive your tach STILL will not work - unless you buy the pre 76 tach.
It is nice to have the other functions on your cluster - oil, volts, temp and fuel but a tach?
I haven't had a working tach in nearly 20 years and haven't needed one.
 
I can get by without the other functions on the dash, but running hay equipment I like to know what my PTO speed is.

I found a cheap tach that attaches to the spark plug wire that should get me close.
 
For the cost of a new block I would be better off to get rid
of the tractor and buy another rowcrop diesel tractor.



I found a spark plug wire tach that should be able to get me
close.



Seems odd that someone would go through the work to
change out the block on a funky little tractor like that.
Hopefully they went through the trouble to do it right and
redo all the other stuff as well.
 
Maybe the original block was damaged somehow and the prior owner found a good deal on an older block. It's not the first time something like that has happened.
 

That s the conversion alternator for the -000 series which drive the tach in the opposite direction from his -600 series
It s his simplest way to have a tach but requires a early model tach
 
(quoted from post at 08:08:35 01/15/23) Here you go right here on the forum you are posting on.
alternater with tach drive
Click to expand...

You don't know if your tach works yet. For $300 you can buy an alternator with tach drive, new cable and instrument cluster. I installed one of these alternators on my '68 4000 but haven't finished other repairs so won't know how it works until Spring. I don't like the way the tach cable comes straight in to the back of the drive so I added a right angle adapter, but that's another story.
 
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