Hey everyone,

I've combed through the archives looking for directions on swapping out the speedo pinion gear, and I found some information but I'm a bit nervous taking on this task as I don't want to wreck anything (cable, gear, etc.) as the parts are so hard to find. I have a 1983 5-speed in my 1971 Datsun, and I finally finished the 4.11 LSD diff (which works great). The speedo gear I have now is 20 tooth, and it's about 10% off, so I'm moving to the 21-tooth version (they don't make the 22 anymore).

(FYI, when I contacted Nissan to order the part, there were only 2 left in the country and it's being discontinued, so if you need one, now's the time to get it!)

My plan is the following...any suggestions?

1) Lift up the rear of the car so I can keep the gear oil in the tranny.

2) Remove the plate and speedo gear housing.

3) Remove the cable from the gear housing.

4) This is where I get fuzzy...will the old pinion gear just come out if I pull on it? I noticed in one of the posts with a picture there was a small pin and the writer said not to lose it...but what does it do? Will it fall out? The link for the post is here: http://www.classiczcars.com/forums/engine-drivetrain-s30/36199-speedometer-o-ring-replacements-tips-needed.html and it's post #4.

5) Put it all back together and drive like crazy as we'll have snow soon!

Thanks in advance for any help you can offer for step #4...

Edited October 28, 201410 yr by z boy mn

it's a roll pin, you will need a very small punch to drive it out.

I've removed a couple of those gears. As Darrel says, a small drift or punch is needed to get the pin started out. I had to use pliers to finish pulling it. It's pretty tight.

You kind of skipped the step of removing the pinion gear assembly/housing from the transmission. They can get stuck also. A big flat bladed screwdriver in the slot will break it loose but large pliers or vice-grips might be needed to completely remove it. Pad the plier jaws, there are many gear housings out there with ugly teeth marks on them. The metal is soft.

If you could, save the roll pin, as this roll pin is Metric size and impossible to find one in US.

Thanks for the tips everyone...I'll definitely try to save the pin. When I had the diff done they swapped from a 19-tooth to a 20, so things have been loosened recently so I hope they're not too stuck. I just want to make sure I don't wreck anything as it doesn't sound like the parts are possible to replace easily. I'll let you know how it goes when the part comes in!

Ic you are changing the pinion, you should replace the o-ring seal on the pinion adapter and the lip seal in the adapter. Don't wont to go to all that trouble and have it leak afterwards.

If you don't have a punch the remove the roll pin, you can use a wood nail from the hardware store. Just file the point flat so its square with the rol pin. It should tap out easy.

Chas

Edited November 1, 201410 yr by EuroDat
Photos

Wow--those are GREAT pics with labels and everything. I do have the seals (I got them from MSA) and will swap them to make sure I don't have any leaks with the new gear. Still waiting for the pinion gear to come in from Nissan--I'll keep you posted!

Happy to give an update on the new site--seems like a huge improvement (and I liked the old site, too!)!

 

Got the new pinion in, and as far as I can tell it's right. The housing had two slots ground into it so the tab on the tranny could hold it into place, and I was able to use one of them keep it in place with the tab. I'm not 100% sure if it's too "tight" (i.e. turned too far), as it turned a bit when I was tightening the bolt on the cable. I called MSA and they said once it snugs up against the gear inside the tranny it won't turn any further, so it should be right. With only 1 pinion gear with 21 teeth left in the country, though, I'd like NOT to burn this one up. Is there a way to test this?

 

Also, I did manage to save the "pin", though for me it was a split pin that was VERY hard to get it out. It didn't really look like the one in the photo, so I'm not sure it's original.

 

I took the car for a run, and the speedo looked terrific. No jumping...all very smooth. I tested it against a GPS and it's only about 2% off (high), and I'm happy with that. After all, the difference between 100 and 102 isn't that big a deal! ;-)

2% off. I think thats better the factory.

Tyre side is also a factor to consider when choosing speedo pinions. A couple of centimeters in tyre heigh can make all the difference.

 

The advice from MSA doesn't sound all that good to me. "Snugs up against the gear". If the pinion is riding hard on the wheel it can do two things:

1- Cause a lot of adapter wear due to the pinion shaft pushing hard to one side.

2- Break the plastic pinion when everthing warms up and the gear gets overstressed.

 

Sounds like your locking tab is a little short and allowing the adapter to rotate too much. Im not sure if that small amount of rotation will cause that much lateral movement.

You can correct it easy enough by removing the locking tab and gently pulling (Don't pull on the cable) the adapter back and re-install it in the correct position.

Chas

Hi Chas, that's what I was thinking, too...that if the gear was too tight, it would do bad things.

When I put it in, though, the new o-ring was tight enough that I couldn't spin the carier by hand (couldn't even get it back out), so I couldn't "feel" when the pinion was in contact with the cog inside the tranny...I could just spin it counter clock-wise a smidge. If I go to far, the teeth won't contact and the speedometer won't work...or, it will strip the gears. Hmmm. Maybe I should figure out how to get it out and put it back in without the o-ring and mark it on the outside somehow, so I know where it should be.

The other problem is I am one-handed at the moment. I had shoulder surgery a few months ago, and my right arm is still pretty useless, so I'm having trouble feeling how things are (or getting them out).

I thought I would add this here as an easy way to keep info together.

I am trying to change speedo drives between different transmissions. Is the metal shaft part of the speedo gear or do the gears press onto the end of the shaft? The transmission I am replacing has a long speedo assembly and the Z transmission uses a shorter assembly. If I can move the plastic gear, I am good. If I can't I have to locate a different drive gear.

That's a good question.  Kind of looks like it might be pressed on.  Or molded.  You might destroy it trying to find out.  MSA's picture shows splines on the shaft.

I have some old ones in the garage.  Maybe I'll dig one out and see.  

https://www.thezstore.com/page/TZS/PROD/21-7183