Dogleg Sending Unit Replacement

[GoGoGo]

So in trying to get my speedometer to work I've already replaced the speedo cable (new Pioneer one) plus tried another good used one and it's clear that something in the sending unit is not working. It's way to hot right now to get under the car and pull out the unit so I'm just seeing if anyone has had some experience with either the unit or pinion gear breaking/not working. 

 

If the sending unit is broken what other unit with bolt right in? The only other one I have is going to be from a 1971 510 auto so I have no idea if that will bolt in? What about the pinion gear in it? Sorry for all the questions but I am a planner by nature and career so like to know the possible next steps before they even have to happen.  :confused:

[flatcat19]

You need a speedo pinion that matches your rear end. 

 

 

Use that to help you search. 

 

This was just answered, again, a couple of days ago. 

[datzenmike]

Speedometer not working... Lots of unknowns and assumptions here. Lets narrow this down some....

 

Disconnect the speedometer cable at the transmission. Have someone watch the speedometer while you twist the inner cable with your fingers. Clockwise I think but try both directions. Does the speedometer even move??

 

NO....... stop right there, you've found the problem. Inner cable may be broken, the dash end is not inside the speedometer head or the speedometer is stuck or broken.

YES..... cable and speedometer seem to be working.

 

While speedometer cable is disconnected, do not screw the outer sheath on just yet. Take note of the position of the notch that the ferule on the cable end would plug into. In the picture on the lower right that would be about  one o'clock.

 

Place transmission in neutral, raise a back wheel and turn in the forward direction. Check cable position. Has it turned????

 

YES.... everything seems to be working

NO...... Plastic pinion gear inside may be broken. Remove 10mm retaining bolt and key and carefully twist and pull pinion sleeve out of transmission and inspect.

 

Easier for you to check later than running off and buying something not needed.

[flatcat19]

I misread the question. 

[datzenmike]

... it's ok Moby.

[flatcat19]

Whoa. 

[datzenmike]

oh yeah, sorry that was Micro.... my bad.

[GoGoGo]

Mike, thanks as always. Somehow I talked my 5 month pregnant wife to slide under the car and watch the sending unit while I turned a back wheel. Sure enough she said that it wasn't turning. Pulled the pinion gear out and it looked like this:

 

 

I'll need to get another one. Where can I get one and how many teeth would you guess I will need to get the speedometer to be more accurate with stock rear end and 195-50-15s? You are the man and I appreciate the help a lot...

[Draker]

I believe I installed a black gear and the needle is reads 65mph when doing 60 with those same tires.

[datzenmike]

The teeth can be counted to be absolutely sure but they are color coded. My monitor shows that as a Green/Yellow color???. Count and let me know what that one is first. The black metal body can be re-used and just the spindle with gear replaced.

 

Lets see what you have now first.

[GoGoGo]

So there are 16 teeth

[Sealik]

http://www.graytechsoftware.com/garage/cogcalc.asp

 

 Nissan Pt #      #T   Color      Ratio   Gears

  32703-78100   16T (yellow)  3.364   37/11

  32703-78101   17T (black)    3.545   39/11

  32703-78102   18T (blue)     3.700   37/10

  32703-78103   19T (white)   3.900   39/10

  32703-78104   20T (red)      4.111    37/9

  32703-86401   21T (purple)  4.375   35/8

  32703-86402   22T (orange) 4.625   37/8

  32703-86403   23T (green)   4.875   39/8

 

  32707-7800 16-19t Sleeve Assy

  3270766300 20-23t Sleeve Assy

[GoGoGo]

So if I do that calculator I end up with a 21T (purple gear) and would have to get a new sleeve assembly!? That doesn't seem right if Draker is using a 17T (black) and is off by 5mph at 60ish. Am I missing something?

[Draker]

I wish I had a picture.. but I'm pretty sure it was black.

[Draker]

I'm pulling the tranny this weekend.. I'll look at it.

[datzenmike]

Tire diameter and differential ratio factor into this. Nissan vehicles don't use the same tires or gear combinations. A 23" tall tire with a 3.354 gear won't use the pinion from a 720 with 28" tall tires and a 3.354

 

I'll have a look tonight when I get home.

 

The sleeve can be reused and only the pinion gear changed. There is a small roll pin to remove and it slides out.

[datzenmike]

The stock 510 tire is 5.60 X 13 so 185/70R13 making the tire diameter 23.2". Your 195/50R15 tires are 22.68" That's 2.3% out. That's nothing. Reading 2.3MPH fast at 100 MPH... nothing. That's 1.15 MPH at 50 MPH. Going up one tooth will slow the speedometer 6.2% which will make it read 3.95% slow at 100 or almost 2 MPH slow at 50.

 

The 16 tooth pinion for a dogleg 5 speed is 32703-N9016 maybe $20 in today's money? It was also used in the April '76 and up A series B-210 GX with the optional dogleg 5 speed. That's the only Nissan that the Yellow 16 tooth pinion was ever used on that will fit your pinion sleeve..

 

 

Never seen one chewed that bad. Check that the speedometer cable is free to turn

.

[Draker]

Here is mine:

 

[GoGoGo]

Thanks to both of you. Ordered the yellow one based off of Mike's calculations and then we'll go from there. Will use GPS to determine how off the speedo is and if I really can/want to correct it. 

[datzenmike]

Keep in mind that GPS speed isn't that accurate. Follow a friend at 50

[GoGoGo]

Yeah so that order was canceled (out of stock). Called the local dealership and it's discontinued. Am I out of luck? Or will another Nissan 16T gear work. Ebay has this one - http://www.ebay.com/itm/Datsun-240Z-260Z-280Z-1971-78-Manual-transmission-4-speed-Speedo-Gear-17-OEM-NEW-/221851654429?hash=item33a763991d&vxp=mtr

 

Transmission is out of a 1977 200SX. 

[datzenmike]

Only the B-210 GX 5 speed has that particular gear. It's in my post

[dscottdatsun]

So what is another proper option outside your fore mentioned piece of unobtainium?

[datzenmike]

I've removed one and they appear to be pressed or molded on and they are likely all the same but mounted on different spindles for the different sleeves. Any other 14 tooth plastic gear could just be 'glued' on to your old spindle. If Nissan doesn't have one then I would start  an ad for any Yellow 16 tooth gear and swap it on to yours.