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Mechanical Speedo drive swap into RB25 Gearbox


Mike Rowe

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I ran the model number for WD21

here's what I got:

 

croppercapture_5_933.jpg

 

Then I ran checked Section 330 of the FAST system for D21 units. There were tons of engines that came in the D21, none being a VG or an RB.

 

but here's what I got:

 

croppercapture_6_752.jpg

 

May not be of great use, but I can tell you for sure that all the 31GXX and the 33GXX are the same unit, but for different years, so if anyone knows what diffs came in the certain years, the gears can be cross-referenced to the years in section 330 of the Nissan FAST catalogue.

 

looks like nissan put special parts on certain cars too that we never new about. all we get are turbo chargers :(

 

croppercapture_7_950.jpg

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What the thread is about is that when you use the RB25 gearbox it has an electronic drive for the speedo. If you want to use the original Z speedo then you need a mechanical drive to put in the RB25 gearbox. The part being discussed is a mechanical insert or pinion assembley that will go in the RB25 gearbox from another (Navara) Nissan model. Is that clear.

 

So we are talking all RB25DET engines from the GTS cars then, just for clarification? So I should be following this thread for final part number and be prepared to do this so I have a speedo on my 260z when Im done.

 

Im not sure what a Navara model is but I saw reference to it as D21. So Hardbody pickups? The ones readily avail here stateside?

 

Thanks

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So we are talking all RB25DET engines from the GTS cars then, just for clarification? So I should be following this thread for final part number and be prepared to do this so I have a speedo on my 260z when Im done.

 

Im not sure what a Navara model is but I saw reference to it as D21. So Hardbody pickups? The ones readily avail here stateside?

 

Thanks

I just ordered one yesterday from Elk Grove Nissan. Part No: 3270202G17 will be here for me some time next week.

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So we are talking all RB25DET engines from the GTS cars then, just for clarification? So I should be following this thread for final part number and be prepared to do this so I have a speedo on my 260z when Im done.

 

Im not sure what a Navara model is but I saw reference to it as D21. So Hardbody pickups? The ones readily avail here stateside?

 

 

 

 

yes to all

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if it's an fs5w71c trans, then no. far as i know, all non-turbo RB25's (or all non-turbo RB's for that matter) came with that trans, ands its not EXACTLY the same in every application (different case designs).

 

if your car has an FS5R30A trans from another car, it will possibly work, pending results of this thread...

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If its the same as the Rb20 as you say, I have read that they already have a mechanical speedo drive. I cant believe that the speedo housing would be physically any different but rather mechanical or electronic, so the same issue would apply.

I would not be going into such detail/concern about a minor item like this, if you have not even decided/started an RB swap.

First decide if you have the money, the will, the expertise and the tenacity to undertake the conversion. This is your major decision to worry about. Speedo cable drive is a long long way down the track.

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Please refer to this page and go to the VERY bottom of the page:

 

http://www.nissannut.com/projects/SAS_3link/

 

You will see the speedometers we are talking about. They appear to be identical to the Z32 electronic speedometer assembly in dimension.

 

I placed my order on Friday and hope to have mine later this week. The next issue will be clearance between the end of the assembly and the tranny tunnel. I do not know if the cable can make that bend.....

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I have two spare FS5R30A trans in my shop. One has the cable type assy, the other has the electronic type speedo drive assy.

They were both sold to me (at different times) as Z31 88-89 turbo Z trans.

 

I can pull them both and take pics if needed?? If that will help, since they are identical to the RB25det trans...

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J. Soileau, thank you for the offer, but since at least 3 of us have ordered a mechanical sender, I would wait until one of us has received it and can compare it directly to the sender in the Z32 trans. The link I provided above has the mechanical sender that we all ordered. At first glance, the red pinion-equipped sender looks identical to the electronic sender in my Z32 trans.

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Will be interesting to see the results here.

 

On a side note...for those who have put the z32 trans in the s30 chassis...would you recommend it? OR should i go through the hastle of finding a 2wd pathfinder / 3.0L 2wd Hardbody or /z31 turbo 87+ trans. These are all basically the same as the rb25 trans, but more difficult to find.

 

I can get the pathfinder one on ebay for about $600 shipped...but mileage and condition won't be fully known...OR i can get a basically newish z32 NA JDM trans that will surely have tones of life.

 

Can i get the shifter far enough forward by cutting the linkage? That shifter linkage really baffles me in how it works (regarding the shaft and the geometry of it...guess i'd have to see it in action to understand).

 

Just thinking out loud...but right now i'm leaning to the z32 trans for availability reasons (plus it's cool to say in the end that you have a z twin turbo trans).

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  • 2 weeks later...

I would like to add that I experimented a little bit and also ordered the speedometer assembly from 1988 300zx turbo. I have a 1988 3.70 LSD differential and this would mean that the assembly would have the correct pinion.

 

Unfortunately, while the assembly body is identical to the assembly for the truck, there is one crucial difference. The 300 zx turbo assembly does not have the little tab that allows it to be bolted to the transmission case. As a matter of fact, I do not see how it is retained in the transmission at all.

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