Jump to content

speedometer pinion help please


Recommended Posts

Hello all . I have a question someone may know? I pulled a 5 speed trans from a 720 pickup I think it was a 85 2 wheel drive I liked it because it had a short tail trans that would fit my 73 620 pickup and it would work with the stock bench seat .

Anyway I need a new speedo pinion the one that was in the trans is trashed . I ordered a new pinion from Nissan but it's to short  and cant be returned :confused:  the pinion itself is a long body total length is 3.50'' inches, black body, pinion is mounted on the driver side tail housing  gear was red in color anyone know a part number ? when I ordered the first part it supersedes to a new part number witch is to short :sneaky:

  • Like 1
Link to comment
  • Replies 9
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

First of all is your speedometer completely accurate? This is the time to correct any problems with reading too fast or slow. It's unlikely the 720 had the same differential gears and tire size as your 620.
 
Your '73 has a totally different transmission and different speedo pinion design in it and should have a 16 tooth pinion but the later 620 with the 71B 4 and 5 speeds (with same speedometer gauge in dash and gearing and tires) this changed to a Red 20 tooth. If your 720 5 speed transplant has a 20 tooth or a Red plastic pinion gear then this is likely the closest.
 
If however when fixed you find that you are traveling faster than the speedo says (needle too low) you can change to a 19 tooth to speed the speedometer cable up about 5% or 2.5MPH at 50 MPH. If too fast a reading a 21 tooth can be used to slow the speedometer cable by about 5%.
 
 

 

 

Be sure to order the pinion for a later 720 transmission. A 20 tooth Red is 32702-58S20 for the sleeve with the 20 tooth gear, for just the plastic 20 toothed gear (cheaper) 32703-78104.  It was also used on the '84 and up S12 (200sx if they can't find it under the 720)

 

To the best of my knowledge this 20 tooth will be correct if your 620 has the same tire size.

  • Like 1
Link to comment

When setting up speedometer pinion gears, you must first get the distance traveled correct.  The odometer has a geared relationship all the way to the rear tires.  This is a constant, that does not change, nom matter how old the vehicle is.  At least vehiciles with mechanical odometers, like our Datsuns.

The speedometer is not mechanically connected to the transmission.  The speedometer needle is attached to an alumnium cup, that a spring holds at zero.  The speedometercable spins a magnet inside the aluminium cup, and induces a electrical current in the aluminium, and this makes the aluminium cup how far the needmlemove in the same direction the magnet is spinning.  

How high the needle reads, in relationship to the speed of the magnet spinning can be adjusted.   The odometer cannot be adjusted in the speedometer.  That is why you have to correct the odometer first, with the speedometer pinion gear, then adjust the speedometer reading.

  • Like 1
Link to comment

Absolutely true. I'm assuming everything is working correctly.

 

Currently I'm having a problem with slowing the speedometer down to read the true speed after a differential gear change. I can not only tell I'm going to slow at 30MPH but confirmed 34 MPH at 50KPH (31MPH) Yes I have a MPH speedo in a KPH country. I currently have a 20 tooth pinion and would really like a 22 but NLA at Nissan. I'm not that worried if the odometer is out or not just don't want the po po stopping me.

Link to comment

Thanks guy's  the question is part numbers the pinions I have ordered are to short for the pinion body am looking for 19 tooth .total  length 3.50  the aluminum body pinion will not make contact with the gear inside the tail shaft . so do I have the right pinion ratio I don't know? I don't have anything to try I know the rear gears were swap to 3.88 works great for a lowered mini .Thanks

Link to comment

32702-58S20 is what I ordered from Nissan it's to short .my pinion is fitted on the driver LH side the old part numbers superseds to the short body .I may have to try and press off a gear or make the new short gear fit the long body and make a short extension to contact the speedo cable .

Link to comment

Thanks guy's  the question is part numbers the pinions I have ordered are to short for the pinion body am looking for 19 tooth .total  length 3.50  the aluminum body pinion will not make contact with the gear inside the tail shaft . so do I have the right pinion ratio I don't know? I don't have anything to try I know the rear gears were swap to 3.88 works great for a lowered mini .Thanks

 

Try turning the pinion 180 degrees. Cut a new notch for the hold down key. I just nicked it with an angle grinder. Sleave now sits upside down to reach the mainshaft speedo drive worm gear.

 

Mikes%20speedo%20pinion%20change%20027.j

Link to comment

32702-58S20 is what I ordered from Nissan it's to short .my pinion is fitted on the driver LH side the old part numbers superseds to the short body .I may have to try and press off a gear or make the new short gear fit the long body and make a short extension to contact the speedo cable .

 

 

Just read this post. I have one of those short 5 speeds but it's from a 4x4 and doesn't have the pinion sleeve in it. I don't know what they use.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.