Mechanical Speedo drive swap into RB25 Gearbox

[HowlerMonkey]

Nissan now sells them with tabs permanently mounted so any "clocking" changes will not take place without a bit of custom work.....they just sell a different one for each application though the gears on 1990 and later (maybe earlier) are removable and the older ones(1984 and older) aren't.

 

Earlier stuff had just a slot where at washer with a flat side holds it in.

 

If you just switch cogs, you will run into depth issues whether crushing gears because too deep or no drive to the pinion because it just doesn't touch.

 

Clocking it is just a workaround to get what you need though I believe nissan sells them with different offset for each gear since I haven't seen one offset other than directly opposite direction from the mounting tab as shown in the pics below.....it's possible but haven't seen it yet.

 

First pic is the S13 automatic sensor (4.08 with pink gear) on the left and a 1983 maxima automatic (3.54)on the right.

 

 

Both the green and black gears have the same amount of teeth and diameter though the sensor on the left came out of the car with the pink one installed......I just put it on top of the black Q45 gear I swapped onto it and I forgot to check the offset of the q45 housing....might do that tomorrow.

 

Even though it seems the pink gear has a different angle, my green gear'd drive on the right slid into the S13 tranny that the sensor with pink gear came out of and worked without binding or slipping while being clocked the exact same.

 

The green one is bored dead center with no offset but you can see the offset of one made to work with a larger diameter gear.

 

In this pic the shaft offset is facing away and you can see that turning it 90 degrees from the other pic would net the same gear depth on the tranny output shaft with the black gear as it would with the pink gear would.....but without the 90 degree change.

 

Though the pic is not perfectly straight, I can assure you there is only offset on one axis.

 

From what I saw on manual tranny sensor/drives, it seems the same offset thingy is going on.

 

In the pics Zedman posted, you can also the same offset scheme going on in the long sensor so we can hope that all nissan transmissions use the same scheme and exploit it.

 

I should have tried to put the smaller 28mm housing sensor from the q45 or J30 into a FS5W71c tranny since it seems all dimensions that I measured were the same other than offset depending on rear gear ratio.

 

I'll compare both to the sensor from my FS5R30a manual tonight and measure it.

 

EDIT: The FS5r30a shorty tranny out of a pathfinder (2wd) that I have has a yellow gear and no offset but it is the same as the long one posted by zedman that has the black gear.

 

The housing has a 30mm outside diameter for this mechanical drive.

 

[getoffmyinternet]

Ah yes. I've only been paying attention to the sensors with long shaft and pinions such as in the rb25 that are not clocked. I couldn't tell you how they engage with different sizes, but I could swear that multiple pinions will work in the same trans unclocked. At least, I thought that a given trans would have multiple combinations of gauges and final ratios... That's interesting though I even saw a few stubby pinions in that other thread and there wasn't any mention of clocking. Not all of them seem to have tabs either, so you'd have to be sure you order the right version.

 

Having a tab on a clocked housing in the first place seems pointless because you defeat the purpose of being able to clock it when you have only one place to screw it in. I guess they designed different transmission housings around a common speed sensor, although each trans only works with one unique pinion.

[HowlerMonkey]

The clocking is a work-around that makes it possible to use more than one gear size per pinion housing.

 

Nissan just has you buy the entire works for each gear ratio.

 

I'm running that little black gear on the housing the formerly held a larger diameter pink...maybe it's white but stained by atf.

 

It surely won't mesh unless I clock it 90 degrees......or buy a housing that might not be easy to find.

 

That is why the original poster had intermittent speedo action....the gear wasn't meshing.

 

Just for reference, here is one from the FS5R30a pathfinder 2wd tranny.

 

30mm outside diameter.

 

[zrookie]

I now have the complete list of part numbers thanks to my Nissan agent

 

 

Nissan Part numbers for different teeth counts.

 

32703-31G21 21 teeth (PURPLE) Ratio 4.375:1

32703-31G20 20 teeth (RED) Ratio 4.11:1

32702-33G19 19 teeth (WHITE ) Ratio 3.90:1

32703-31G18 18 teeth (BLUE) Ratio 3.70:1

32702-33G17 17 teeth (BLACK ) Ratio 3.545:1

32702-33G16 16 teeth (YELLOW) Ratio 3.364:1

 

Good information, I saw your project very nice, but how did you mounted the sensor to the tranny?

[mtnickel]

For some reason I thought you order the pinion with a stock (black) gear and then get the proper gear afterwards to attach on. Not the case, the part numbers in the post above are for the entire pinion assembly with the gear listed.

Anyways, I have a black pinion if anyone wants it for cheap. Needed a white gear for the 3.90 I'm putting in.

 

Mark

[mtnickel]

As another clarified post,

the 32702-33GXX (XX being the number of teeth) is the shorter pinion which was said to fit RB25 non turbo.

the 32702-02GXX is the longer one (navara) that fits the RB25 TURBO box.

 

I tried to order the 02G19 but they stated there are none in the country. My local canadian parts guy claimed you could order it from japan and it would be here in 1-2 months, but who knows if that's true.

the 32702-02G17 is much more common and I got one at FRsport. You can order that for the pinion assembly and then maybe try and get the toothed shaft. That part number is 32703-01GXX. Those too are in really really low if not non-existant supply, but I may have found 1 19 tooth shaft out of Georgia.

 

Also, regarding that part number, it looks like the above list may be a typo:

 

32703-31G21 21 teeth (PURPLE) Ratio 4.375:1
32703-31G20 20 teeth (RED) Ratio 4.11:1
32702-33G19 19 teeth (WHITE ) Ratio 3.90:1
32703-31G18 18 teeth (BLUE) Ratio 3.70:1
32702-33G17 17 teeth (BLACK ) Ratio 3.545:1
32702-33G16 16 teeth (YELLOW) Ratio 3.364:1

 

From the parts diagrams I have looked at if it is a 3270 '3', it is just the pinion shaft/gear (not the housing). I'm guessing if you wanted the entire assembly you would order 3270 '2' - 33G21.

 

This site is really quite handy:

http://www.partsbase.org/nissan/

It lets you put in a part number and it will show you which model (and it's respective country) has a diagram with the part. When I asked the nissan parts counter guys, they too didn't even know what vehicle a certain number part corresponded to.

 

Finally, if you can't find the parts, there is a DIY on the skyline sites where you can pull the red gear (4:11) off the electronic stock shaft and fit it onto the mechanical pinion assembly if you have it. In that way you could choose between 3.54 (stock black) and 4.11 (red). only 5% off for anything from 3.36 up to 4:30.

 

Not sure if there are any other gears that can be used in the same manner. The shorter 33GXX shaft gear won't work retrofitted on the navara shaft either as the pitch of the teeth goes the opposite direction.

 

Anyways, that was lengthy, but hope it provides some clarity and ideas for people trying to match up there diff and RB Trans.

 

 

Edit: One final Note:

Here are some things I found helpful when swapping the original RB red gear onto the mechanical housing. I used this guide as a reference:

 

http://www.jdmlegion.com/KnowledgeBase/Engine%20and%20gearbox%20conversions/Making-a-mechanical-speedo-sender-for-the-RB25-gearbox-f0271b89-cd6e-425d-bc0a-ee62f51dfaa7

 

Tip 1) For drilling out the red gear, I didn't have the exact size bit and you don't really want to take off additional material. So what I did was punch out the drift that holds the electric shaft in place. Then with a little muscle, i pulled that shaft out of the assembly (this will ruin the sensor as the shaft is glued into the sensor). I then took an angle grinder and cut an angled notch into the end of the shaft so it's sharp. In this way, I created a little cutting head. I then used this to drill out the the flat part of the red gear. (My first idea was the ideally just swap the shafts entirely by machining the the opposite end to accommodate the speed-o cable, but it looked too involved if not impossible)

 

Tip 2) If you put the red gear onto the mechanical shaft as is, you will have to a) hit the gear with a hammer/mallet, and push the toothed portion through the entire assembly. 2 things I did not like. So I again punched out the retaining drift pin and pulled the shaft out. Now, you can put the shaft into the gear backwards and you only have to pound the splined section the required distance. Also, you can nicely support the entire bottom area of the gear and hit the metal shaft as not to fatigue the plastic as much. Sorry I don't have pictures, but I hope that all makes sense.

 

Tip 3) VERY Important! The speed gear is offset to accommodate all different gear sizes. I believe it is critical to have the mechanical housing "clocked" correctly into the transmission so you have the correct amount of gear interference, but not so much so that it binds. When you install into an RB housing install it first with the most slack. Make sure everything is nicely lubed up, but the shaft and the other housing. Now you can rotate the entire housing and if it twists smoothly enough you can feel when it "bottoms out" where the gear is not tight to the internal gear. I twisted until it was tight and then backed off just a smidge as a safety measure. You can also use a needle nose pliers and try and push/pull the pin a bit to see if it is binding (there is about an 1/16-1/8" of shaft movement available).

 

Tip 4) Finally, when you have it clocked properly, score the assembly and the transmission. Push or pull the assembly so that it's depth matches the factory (probably the same depth as the other notch in same housing). Now that its sitting both at the right height and rotated for optimal gear meshing, I took a 1/16" angle grinder and cut into the housing flush with the mounting surface on the RB Trans (where the original bolt secured the housing). I probably cut around 1/8" or so. then make that notch nice and flat with a file (to take out the radius made by the wheel). After that it's just a matter of creating a washer/scrap piece of metal that slides in tight to the notch, then drill a hole in that washer that bolts up to the stock location. The idea is to create a washer/notch system that stops the assembly both from coming out, but also rotating. You could probably fashion some sort of vertical tab as well if you desired.

 

That is all!

Edited May 26, 2014 by mtnickel

[HowlerMonkey]

That post belongs in a wiki entry or something.

 

Thanks for the information.

[datdudecarter]

So I know that I'm like twenty years late with this comment, but hopefully one or all of you guys get this... I remember someone mentioning this as a possible issue but I never saw or read anything more about it. And since I recently installed my RB turbo trans into my car, I remember thinking the same thought.

 

Show me some pictures of the Narvara Speedo Pinion set installed into the trans on a S30Z. Are there not any clearance issuses on the sides of the tunnel?? Because from what I remember from looking at my trans on my back was that it was close against the tunnel. Very. So how that cable would screw in..... I'm not sure. So show me some pics please Gents! Thanks.

[illusioneclipse]

I bought 32702-33G17 but it seems too long for my RB20 transmission?  Did I buy the one for the RB25det transmission?  What's the right P/N for RB20 transmission for a stock 78 280z speedometer?