Rb25 Gearbox Into R32

[kudos.motorsports]

It might cost a little more, however you can't go wrong with an R32 GTR speedo drive unit. Just remove the electic R33 item, install the GTR item and away you drive with a working speedo.

[Dahtone Racing]

whats involved in doing this conversion??

tail shaft etc etc?

oh and how do i tell if what im buying is really a RB25DET box?

Edited September 30, 2006 by 2GU UP

[lwboosted]

the main things that need to be done is, shorteneing the tailshaft and putting a r33 yoke on the tailshaft so it fits in the box, you need r33 slave cylinder and a custom cross member... very simple to get working.. use same clutch fly etc... the only crap part is the speedo...

oh you can tell the difference in the boxes as the r33 box looks like a r32 box that has been blown up like a ballon.. big size difference...

Edited October 1, 2006 by lwboosted

[Dahtone Racing]

what needs to be done the the cross member?

[Bl4cK32]

mines just a piece of rectangle tube with 2 bits of angle welded to it

[B0oStEr]

There are a few ways to make the speedo work with an r33gtst box in an r32gtst.

For the speedo to be 100% you need a 21 tooth gear but I don't know which nissan part no. fits.

Maybe ask Neo32.

You cannot use gtr or gts4 gears as they are cut the wrong direction.

The cheapest solution is to use the red 20 tooth gear from the electronic r33 sender on the navara pinion assembly part no. 32702-02G17.

Your speedo will read about 5% over so at 100kph your speedo will read 105kph.

You need to carefully cut the black plastic 17tooth gear from the navara unit.

Remove the circlip from the the r33 unit and pull the red gear off.

You will notice that the end of the r33 spindle has a flat half circle section machined on it.

The red gear has a mating half circle hole up the centre.

I opened the hole to a full circle with a round file being careful not to make the hole any larger, just perfectly round.

The gear will now be a tight interferrence fit over the splines on the navara shaft.

You will not need glue if you have opened the half round hole carefully.

Now for the very important part that nobody seem to have mentioned so far.

Think about it.

The navara speedo drive originally had a much smaller gear and you have replaced it with a larger gear.

The reason that this conversion fails for so many people is because they don't address this issue of different diameter gears.

For the gears to mesh correctly the spindle has to be in the right position for the gears diameter.

Look at the hole for the spindle in the body of the speedo drive and you will see that it is off center.

Rotating the speedodrive in the gearbox housing will move the gear in closer or further away from the drive gear inside the gearbox.

For the gears to mesh correctly using the navara speedodrive and the red 20 tooth gear from the r33 box you will need to recut the slot that locates the speedo drive in the box exactly 180 degrees opposite the original slot.

If you don't do this the gears will mesh too tightly and be deflected until they fail.

I recut my slot using a hacksaw and cleaned it up with a narrow file.

[kudos.motorsports]

No cross member modification is required just use your RB20DET item.

[B0oStEr]

As far as the cross member is concerned the r33 gtst five speed is a straight bolt up swap in an automatic r32 gtst but in a manual r32 the holes in the floor for the cross member are about 50mm further forward so although the cross members are all the same they will require modifications for a manual to manual swap,

[lwboosted]

  Quote

Now for the very important part that nobody seem to have mentioned so far.

Think about it.

The navara speedo drive originally had a much smaller gear and you have replaced it with a larger gear.

The reason that this conversion fails for so many people is because they don't address this issue of different diameter gears.

For the gears to mesh correctly the spindle has to be in the right position for the gears diameter.

Look at the hole for the spindle in the body of the speedo drive and you will see that it is off center.

Rotating the speedodrive in the gearbox housing will move the gear in closer or further away from the drive gear inside the gearbox.

For the gears to mesh correctly using the navara speedodrive and the red 20 tooth gear from the r33 box you will need to recut the slot that locates the speedo drive in the box exactly 180 degrees opposite the original slot.

the reason my cog cracked is because the hole i made was too tight, and split the cog when pressing it on....

wow this is very interesting... i will source a new cog and do what you have just done with picks... then write up a DIY. does any1 know where to get the 21 tooth cog from??

Edited October 2, 2006 by lwboosted

[Dahtone Racing]

any one got pics of the cross member mods required?

also anyone know of any number or anything i can check on the box to make sure its an RB25 one?

[RB25HR31]

guys i purchased the 32 gtr assembly brand new, put it in and it failed after 160kms. i only realised the teeth are cut the wrong way after i pulled it out the 2nd time.

whats the process with the r32 gtr sender?

i still need to swap the cogs correct, use glue and such??

[Bl4cK32]

cut the buff coloured gtr cog off and glue on the r33 red speedo sender cog.

Make sure u give it enough time to cure properly as it could come off again...

[RB25HR31]

ok. have my other shaft and cog on order....so should all be good by end of week.

i just wanna know what glue you guys have used (exactly).

cheers.

[RB25HR31]

anyone. what glue you guys use?

[lwboosted]

i used aroldite.. but u have to make another cut for the locator or the cog will fit too tight and break off.. mines been in for a couple of months now and it all good..

[neo32]

i purchase a 21 tooth nissan sender from nissan ex japan but unfortuanaly they dont make them anymore

if u look at the niviara speedo drive part number teh last number says 17

i just changed that to 21 and walla

and that was 2.5 years ago straight bolt in no problems

[BHDave]

Just throwing this out there as i'm about to do this conversion myself (even though my 20 box is holding up rather well behind the 25)

I measured up and found the 25 box was about 10mm shorter overall than the 20 box. From what I could see without removing the 20 box and tailshaft you would actually need to lengthen the tail shaft assembly to suit. Either way before i let someone chop up my tailshaft i'll do a proper measure.

The other thing is; Has anyone considered grafting a speedo drive out of a 33 or s13 in the dash and using that with the stock r33 sender? I'll be jury rigging mine so that i can have speed on my pfc handset in the short term but was just thinking about an alternative solution.

Quick edit; does anyone know whether the rb20 and rb25 boxes use the same thrust bearing carrier before i start searching for a new one?

Cheers

Dave

Edited January 28, 2007 by BHDave

[Bl4cK32]

  BHDave said:

Quick edit; does anyone know whether the rb20 and rb25 boxes use the same thrust bearing carrier before i start searching for a new one?

Cheers

Dave

bearing carrier depends on box used and type of clutch. I had to fit a new one to suit my r33 box + the os twin in my 32

[BHDave]

Just adding to the knowledge base while the info is fresh in my mind (still haven't done the speedo or wiring but box is in and bolted up)

I went for a 1 piece tail shaft from hardie spicer. set me back $575. If you can get the front half of a 33 shaft the uni is the right size to bolt up to the diff and obviously the yoke is right so it's good for a sample. I measured from end of the output shaft on the 25 box when it was bolted up to the diff flange and it's 1275mm (this is for a non abs car). As Bl4cK32 has stated elsewhere, you can get a shaft made up at the same length as the original manual tailshaft and it'll work fine as there's bugger all difference between the lengths but if you want to be pedantic.....

I also had to bend the top of the transmission tunnel up a bit to clear the top of the box. Theres a brace that runs around the tunnel about 100mm forward of the shifter hole that fouled on the top of my box. A jack and bit of 1 inch square section steel fixed that.

Crossmember was as stated earlier in this thread. Welded a couple of 50mm wide straps to the rb25 crossmember (it was the same as the 20 one as far as i could tell) and drilled some new holes about 50mm further forward. I had to grind a few mm off the inside edge of one side as it fouled on the box otherwise.

Thrust bearing is the same size between the 2 boxes, I didn't think to check if the carriers or clutch fork were the same.

And lastly, some of the bell housing bolt lengths were different. I used a combination of the existing bell housing bolts and old slave cylinder bolts and ended up one short, which i am yet to replace. It's one of the bottom ones so easy to get to when i do wiring.

I'll update on the success or failure of the speedo conversion

[dangerous_daveo]

Man thats exxy for the tailshaft, unless they used some real nice unis. Mine was only about $350.

I asked about doing the electronic speedo thing, seemed like far too much hard work, and WAY too much money. If your doing it yourself it might not be so bad. But seriously my navara $22 speedo drive with the R33 cog works a treat, its about 5kms out at 100kms which I think given all the other things changed with the car is pretty darn good.