Staggy Rb25det 4wd Front Cut

[zertek]

OK. my front cut was delivered today. At work at the moment so i cant get pics atm.

I will be dropping this engine (RB25det AWD sump) into my R32 GTS4.

First 2 questions:

- Are the 25det staggy 4wd sump ratio's different from my rb20det 32 4wd sump ratio's

- There is a button behind my steering wheel on the staggy front cut with a picture of the AWD train (will get pics up soon) any one know what this button used to do??

Cheers guys.

[zertek]

no one knows?

i know the gts4 sump is better than the gtr (ratios), what about the sagea ratios?

[blind_elk]

Ratios are different. Staggy = 4.083, R32 = 4.375 . You MUST match the front and rear ratios.

I stuck the Stagea ratios in (had to get new rear diff, swapped crown wheel and pinion onto R32 centre) because I found the RB25DET has waaayy too much torque to need 4.375 ratios.

NFI about the button.

[Duncan]

the button locks F:R torque at 50% for snow/ice conditions. I assume you would need the stagea atessa computer and pump as well...plus you can't really use it the rest of the time as it would burn the clutches out.

[zertek]

EDIT: misunderstood something

Ratios are different. Staggy = 4.083, R32 = 4.375 . You MUST match the front and rear ratios.

I stuck the Stagea ratios in (had to get new rear diff, swapped crown wheel and pinion onto R32 centre) because I found the RB25DET has waaayy too much torque to need 4.375 ratios.

NFI about the button.

Ok im an extreme newbie to the drive train..... So if i was to bolt the 20det sump ratio's (4.375) onto my 25det and leave my rear diff ratio's on my 32 standard i shouldnt have any problems? It's an unexperienced guess, but wouldnt it be beneficial (performance wise) to keep the better ratios of the 32?

Edited June 7, 2007 by zertek

[blind_elk]

Yes, if you are happy to keep the 4.375 ratios, then you only you need to swap the front diff from the RB20 into the RB25. It's easier to swap the actual diff rather than swap the whole sump - no guarantee they are interchangeable. Simply remove the front cover from the diff housing, and the diff almost falls out. Have fun undoing the nut on the pinion (it is matched to the crown wheel on the diff carrier, so it needs to swap also).

If you really need rapid acceleration, then stick to the R32 ratios. Frankly, I have found that the RB25DET has more than sufficient torque / power to accelerate a R32 pretty quickly. If you do the swap to the Stagea ratios, you will need to have the crown wheel and pinion for the rear swapped onto the RB20 centre in the RB20 housing - the housings are slightly different externally, and the Stagea is a 5-bolt driveshaft flange (R32 is a 6-bolt flange).

If you do swap to the Stagea ratios, you will (eventually) need to replace the speedo drive gear in the gearbox - speedo will read about 5k UNDER at 60, ie 55 indicated = 60 actual. I'm using a GT-R one (it's close enough, considering speedo inaccuracy).

[zertek]

Yes, if you are happy to keep the 4.375 ratios, then you only you need to swap the front diff from the RB20 into the RB25. It's easier to swap the actual diff rather than swap the whole sump - no guarantee they are interchangeable. Simply remove the front cover from the diff housing, and the diff almost falls out. Have fun undoing the nut on the pinion (it is matched to the crown wheel on the diff carrier, so it needs to swap also).

If you really need rapid acceleration, then stick to the R32 ratios. Frankly, I have found that the RB25DET has more than sufficient torque / power to accelerate a R32 pretty quickly. If you do the swap to the Stagea ratios, you will need to have the crown wheel and pinion for the rear swapped onto the RB20 centre in the RB20 housing - the housings are slightly different externally, and the Stagea is a 5-bolt driveshaft flange (R32 is a 6-bolt flange).

If you do swap to the Stagea ratios, you will (eventually) need to replace the speedo drive gear in the gearbox - speedo will read about 5k UNDER at 60, ie 55 indicated = 60 actual. I'm using a GT-R one (it's close enough, considering speedo inaccuracy).

Ok, thank you

~Im also using a GT-R gear box. does my box need to come out during any of this??? I've heard its extremely heavy and not easy to remove/install?

~For the last 15 minutes ive been searching for a tech article on how to interchange the sumps (looking for GTR's swapping to a GTS4 sump) just for the general idea.... no such luck yet so if anyone knows of any good tech threads that show interchanging 4WD sumps, care too share??

[blind_elk]

I managed to do the swap with the gearbox still in the car, ie seperate engine from gearbox, lift engine out.

AFAIK, there isn't any articles on the sump swap. The sump doesn't use a gasket, it uses special sealant. Much safer, and simpler, to only swap the actual differential units (even if the nut on the pinion is torqued to VFT).

If you want to swap the whole sump, it will be basically "undo nuts, remove sump, fit new sump, do up nuts".

[zertek]

If you want to swap the whole sump, it will be basically "undo nuts, remove sump, fit new sump, do up nuts".

think ill go with that option when the time comes... Does anyone know where i can find a service manual for a car using the rb25det, (stagea or R33) For a bit of wiring help???

[Duncan]

its cool we do sump swaps all the time.

Undo all the bolts, then carefully scrape all the liquid gasket off (you can buy gasket remover but a razor blade does the same thing). You can buy new liquid gasket anywhere loctite and others make it. A line of the asket around the sump, tighten it back up and off you go.

blind_elk if you swap the diff centre don't you have to adjust it back up again afterwards to avoid backlash?

[blind_elk]

blind_elk if you swap the diff centre don't you have to adjust it back up again afterwards to avoid backlash?

When I did the initial install, I didn't concern myself with that (maybe I should have, but it seemed to work ok). When I swapped in the Stagea ratios, I had both ends done professionally, so I guess they were set up correctly.

[zertek]

its cool we do sump swaps all the time.

Undo all the bolts, then carefully scrape all the liquid gasket off (you can buy gasket remover but a razor blade does the same thing). You can buy new liquid gasket anywhere loctite and others make it. A line of the asket around the sump, tighten it back up and off you go.

blind_elk if you swap the diff centre don't you have to adjust it back up again afterwards to avoid backlash?

sounds easy enough.... but then again nothing is ever as easy as it appears:P still... im gonna give it a go! cheers

[Duncan]

BTW zertek your avatar is in pretty poor taste.

[GTS4WD]

Wait.. Let me get this right.

R32 GTS4 front diff will give better acceleration?

I just completed a conversion in my 32 GTS4 and used a Stagea RB25DE and kept the staggy front diff.

Is there anything wrong with that?

If i was to swap the front gears from the staggy to the 32 gearing ill get better acc. ?

Would this be why my Torque Split Guage reads a constant 6? or is that just rooted?

[Duncan]

Yeah mate that is a real bad thing....your transfer case doesn't have long to live - there should be no front torque at least 90% of the time.

Worst of all you need to take the sump off to change the front diff, so it will probably be easier to change the rear diff to a stagea one now

Shorter ratio (higher number:1) = faster acceleration

[GTS4WD]

oh ****

How badly does it damage?

Edited June 14, 2007 by GTS4WD

[Duncan]

the transfer case has a series of clutch plates which transfer torque to the front, and they aren't really suited to continual use.

After a few seasons of racing I had mine rebuilt recently, budget 500-1000.

But if its still working now its not too late - just stop driving before you damage it further and decide if its easier to change the front diff back to standard sump (engine out) or put the stagea diff in the rear (not sure if it bolts right in).

If you did the engine swap yourself it may well be easier to take it out again since you've had the practice - the other option you need to buy a new diff & hope it fits ok

[GTS4WD]

Thats strange.. because I remeber cheaking the gear ratio's and both came up the same.

I did this by holding one drive shaft entry point and turning the crank a full rotation. Both front diffs (from the 20DET and the 25DE) were the same. i.e both of them stoped at the same point.

Could the ratio's be different between the 25DET and 25DE's?

ATTESSA seams to engage and disengage fine. And the car drive like a normal RWD all other times. The driveline felt no different after the swap than before the swap.

I reaf that by only doing this once. A very minute difference will be very pronounced at higher RPM and speed. Am i correct in saying this?

Edited June 15, 2007 by GTS4WD

[blind_elk]

Thats strange.. because I remeber cheaking the gear ratio's and both came up the same.

I did this by holding one drive shaft entry point and turning the crank a full rotation. Both front diffs (from the 20DET and the 25DE) were the same. i.e both of them stoped at the same point.

Could the ratio's be different between the 25DET and 25DE's?

We're talking only about 7% difference here, and over a 1/4 axle turn (= 1 crankshaft revolution), I doubt you are going to notice that 7% variation.

ATTESSA seams to engage and disengage fine. And the car drive like a normal RWD all other times. The driveline felt no different after the swap than before the swap.

But you said before:

Would this be why my Torque Split Guage reads a constant 6?

So either it's all ok, or it's not all ok

I reaf that by only doing this once.

?????

A very minute difference will be very pronounced at higher RPM and speed. Am i correct in saying this?

It's roughly 7%. So when the rear is doing 100kmh, the front will only be doing 93. (rear at 60, the front will be doing ~55)

The Stagea rear diff is externally slightly different to the R32. It's rumoured the Stagea doesn't have any form of LSD. So, it's probably safer to have the Stagea gears transferred to the R32 centre in the R32 diff housing. The front diff can possibly be removed with the engine in place - simply remove the front cover and the centre almost falls out (after removing drive shafts, which you have to do anyway).

[Duncan]

yeah all stagea auto are open diffs, the S2 manuals had an lsd but would be very hard to find.

I'm also confused if you are having trouble or not. front torque all the time is real bad. if you normally have 0 you are fine.