RX Clutch LSD change ratio

AndrewT · Post by **AndrewT** » Tue Oct 24, 2006 10:17 pm

I want to get my RX Clutch LSD centre, and put it inside my 4.111 open centre casing.

I've heard there is a step-by-step instruction guide somewhere for doing this - anybody know where it is on the net?

thanks

cruzingbrumby · Post by **cruzingbrumby** » Tue Oct 24, 2006 10:22 pm

from USRM
same procedure for 4.11 you need E10 1/4 drive long torx socket $30 from SNAP-ON, I haven't found in any tool shop yet

Remove stub axles by removing the two bolts from inside of axle.
Then drain and remove rear cover.
Check for excessive metal or other chunks.
Remove the side bearing caps and mark them(left and right).
Keep them with the rear end they came from.
You will need to reuse the 3.90 side caps with the 3.90 ring gear.
Next remove the diff unit by rotating and pulling towards you.
You will see 10 bolts(I think) You can get these apart using a wrench and a breaker bar if you do not have a vice.
Remove the 3.70 RG and set it aside. Repeat the procedure for the 3.90 diff.
Take the 3.90 RG and place it on the LSD unit.
This where it can get tricky.
I have run into this a couple of times.
The bolts may be a little bigger or a little smaller than the holes in the diff.
If they are the ones that are a little bit smaller you will be ok.
If they are a little bigger then you will need to open the holes a little bit.
If needed do this now. Clean unit again.
Now you can start to assemble the "NEW" unit.
Be sure to use the "Loc-tite" of your choice,
I used the blue stuff.
Get these as tight as you can and all will be good.
After you have the diff unit removed from the 3.90 case wipe it out.
Then place a rag or the like and cover the pinion gear and bearing.
Look at the two empty cases and compare both and you will see where it is ground down to accommodate the LSD.
You need to replicate this cut-out in the 3.90 case.
After you think you have removed enough material do a test fit.
Now wipe it out again and use some brake clean to make sure you have all debris out.
Use brake clean because it will evaporate. Now install the unit.
Now would be a great time to replace the side seals.
Also make sure to reinstall the rubber pieces that go over the axle stubs.
Make sure that you use the side caps that match the ring gear.
Very important as this will maintain your gear mesh.
If it isn't the right set you run the risk of getting noise and mismatch.
Install the bolts in the side caps and then install the rear cover.
Take out the top "fill" plug. I run Kendall limited slip gear oil.
Fill to recommended levels and then install it in the car.
Go drive and enjoy the new "traction" advantage.

SuBaRiNo · Post by **SuBaRiNo** » Tue Oct 24, 2006 10:36 pm

Used to be on the USMB with good pics... not there anymore.

Dave

BrennyV · Post by **BrennyV** » Tue Oct 24, 2006 10:49 pm

:O yehhhh easy......... hmmmm
sounds like soe fun andrew

SuBaRiNo · Post by **SuBaRiNo** » Tue Oct 24, 2006 11:51 pm

Having done it before... it's seriously not the hardest thing i have ever had to do. And giving the right tool (that i am lending you) u should not have a drama.

Dave

BrennyV · Post by **BrennyV** » Wed Oct 25, 2006 12:14 pm

well ill ave to have a gander i spinx...

AndrewT · Post by **AndrewT** » Wed Oct 25, 2006 7:43 pm

Tackled it today.
Yes its all very straight forward, pretty easy.
One problem though...

I'm up to the stage where im putting my desired ring gear onto the LSD (my 4.111 ring gear). Sure enough the LSD part needed the holes drilled larger to accommodate the different bolts. Everything was going fine, tightening up all the bolts nice and tight with lock-tite on them... then one of the bastards stripped. (I hadn't even done that one up very tight yet either!)
The bolt has a few threads totally flattened and so does the thread in the ring gear.

I'm going to go into a diff place tomorrow and see if they can tap it for me and supply a new bolt.

**thanks Dave the Snapon tool works a treat!

AndrewT · Post by **AndrewT** » Wed Oct 25, 2006 7:49 pm

Another thought...
I actually have another complete 4.111 diff sitting here but it's a way later model (female axel stubs etc). I might take the ring gear out of that and bring it to the diff place as well. I'll get them to verify that it's exactly the same and if it is then I'll use that.

AndrewT · Post by **AndrewT** » Thu Oct 26, 2006 5:45 pm

Well it's done now.
I got that stripped thread cleaned up abit but theres no way to fix it properly. It's extremely high tensile cast metal, impossible to put a helicoil in.
The offending bolt is done up fairly tight, and with heaps of the highest strength Loctite on it.
Seems to drive okay, no worrying clunks or anything yet (only test driven about 10km so far!)

Few interesting points...

1 - In the above guide it says,
"Make sure that you use the side caps that match the ring gear.
Very important as this will maintain your gear mesh. "
That makes sense to me so thats what I did.
But in another guide on USMB theres an exploded diagram and they rekon your supposed to use the side caps from the LSD??
Oh well, it seems to work.

2 - I pulled apart that late model 4.111 diff I had...Not suitable. The ring gear is the right ratio but its a different diametre. No way for it to fit.

I've found myself another 4.111 Open diff (early model) in Sydney so I'm getting that sent over. I'll swap the LSD into this when it arrives and hopefully no threads wil strip this time!!

Subafury · Post by **Subafury** » Tue Oct 31, 2006 11:19 pm

im after some info on LSD.
is the LSD in the RX a 3.9 ratio? and isnt that slightly worse (apart from the whole lsd part) than the stock 3.7 in the L?

also RX's ar pretty rare hey?

Fang · Post by **Fang** » Wed Nov 01, 2006 5:55 am

subi wrote:im after some info on LSD.
is the LSD in the RX a 3.9 ratio? and isnt that slightly worse (apart from the whole lsd part) than the stock 3.7 in the L?

also RX's ar pretty rare hey?

LSDs out of RXs are 3.7 ratio. 3.9 would give a better take off but engeine revs more at 100kph.

RX diffs are relatively rare in Australia - hence their hefty price tag second hand. Even Datsun users have been snapping them up.

Xtreme_RX · Post by **Xtreme_RX** » Wed Nov 01, 2006 9:08 am

Fang wrote:LSDs out of RXs are 3.7 ratio. 3.9 would give a better take off but engeine revs more at 100kph.

I never noticed any RPM difference on the highway with 27" tyers...

AndrewT · Post by **AndrewT** » Wed Nov 01, 2006 2:22 pm

There would definitely be an RPM difference, there has to be. But I've heard it's not even noticable.
RX's weren't a massively widespread car even when new, so now finding the diffs out of them is fairly difficult aswell.

Subi if you find an RX rear diff it would be 3.7 which would match your car - could be installed in about 5 minutes.

Phizinza · Post by **Phizinza** » Wed Nov 01, 2006 5:28 pm

AndrewT wrote:could be installed in about 5 minutes.

But more likely over an hour in my experience. The inner driveshaft cups don't like coming off. And sometimes the propshaft doesn't either. Only way I found around this was with a BFH.

I've heard LSD's need more care with shimming. Maybe this is why the other way says use the LSD side caps. Although taking it to a diff shop and getting it shimmed correctly would make it last longer. Or if you have the shims and tools you could do it yourself.

SuBaRiNo · Post by **SuBaRiNo** » Wed Nov 01, 2006 8:07 pm

I never noticed the RPM difference either with the ratios.

AndrewT said "could" be installed in 5 minutes... "should" take a bit longer. As stated... if the diff has never been removed in 20 years chances are the CV joints wont come off easily and neither will the tail shaft.

Dave

Fang · Post by **Fang** » Wed Nov 01, 2006 9:52 pm

There will be a difference - noticeable or not.

D3V1L · Post by **D3V1L** » Wed Nov 01, 2006 10:38 pm

so troo..hehe....long time spend gettin the first diff off...lol...but every diff after that was quite quick;)..id be a good contender for the 5 minute swap over..ahhahaha

dave

SuBaRiNo wrote:I never noticed the RPM difference either with the ratios.

AndrewT said "could" be installed in 5 minutes... "should" take a bit longer. As stated... if the diff has never been removed in 20 years chances are the CV joints wont come off easily and neither will the tail shaft.

Dave

AndrewT · Post by **AndrewT** » Thu Nov 02, 2006 2:36 am

It makes more sense using the side caps which match the ring gear and casing because these particular shims determine how the ring gear matches up to the pinion and if all these are the same as before then everything should still be perfectly alligned.

....heh, yes obviously I am aware of the usual minor problems with removing a diff. I had D3V1L Dave on my mind when I wrote that. I guess Matt's probably hasn't been removed in a very long time so there probably will be a slightly longer time involved in popping the inner cups off etc. But who knows, they might just come straight off. I am as always an optimist and usually nothing cannot quickly be solved without a trusty mallet!

Phizinza · Post by **Phizinza** » Thu Nov 02, 2006 4:30 pm

AndrewT wrote:I guess Matt's probably hasn't been removed in a very long time so there probably will be a slightly longer time involved in popping the inner cups off etc. But who knows, they might just come straight off.

The first time I removed the rear diff in the Brumby I left the cups on and pulled the axles apart (as the spare diff came with cups on it. And I couldn't get them off) Made for a quick swap. Then I welded up another diff and when it came to swapping the cups just fell off my old diff. So it seemed a few months of driving worked them lose. Bit weird, but hey, I didn't mind.

Subaman · Post by **Subaman** » Fri Nov 03, 2006 8:56 am

It makes more sense using the side caps which match the ring gear and casing because these particular shims determine how the ring gear matches up to the pinion and if all these are the same as before then everything should still be perfectly alligned.

Just get a 3.9 diff, pull the cetre out and fit the LSD centre and put it back together again exactly as it came apart using the same shims in the same places, and thats all there is to it,Never undo the pinion bearing nut, thats the one that sits in behind where the tailshaft bolts to the diff.

Cheers
Grant