3/S rear differential discussion, the "H", "G", and the "J" specs, is it JDM, US, UK?

[J. Fast]

Might be a cool thread to discuss for a while. A few of us in Colorado have been toying with drivetrain regearing, hybrid diffs, and rear lsd options. I have a few tech'y observations and questions regarding 3/S TT rear differentials.

First few...

The "G" series rear differentials. Those are USDM standard viscous rear lsd's. There are two types:

Type 1) "3" series
Type 2) "4" series

Correct me if I'm wrong here... The numbers on the rear differential stamp plate identify the drive and pinon gear in the diff housing. The "3" series belongs to a 5 speed and "4" series identifies U.S. 6 speed, right?

First question... How many teeth are on the drive gear and drive pinon in the 5 speed rear diff, and the respective 6 speed? Pics anyone?

Now the mind puzzle... The "H" series rear differential. Those are OEM JDM rear torsion helical locking lsd's. There are also two different types/styles (if you will) of gearing in these rear differential.

Type 1) "3" series
Type 2) "4" series

Correct me if I'm wrong here... The numbers on the diffs identify the drive and pinon gear in the rear differential. The "3" series belonging to a 5 speed and "4" identifies a 6 speed. Well, what are the drive gear ratios for these? Actual pics anyone?

I have "heard" there are only two rear differentials for the 3/S TT. So the mind puzzle to unwrap is... how many teeth are on the hybrid rear differential drive pinion and hybrid drive gear?

Call me crazy but what I'm thinking is this, there are 3 different rear differential options available for the 3/S TT. Reasoning? There are three different teeth/styles of ring and pinions available to the TT 3/S. 5-speed, 6-speed, and JDM (MR) 6-Speed. The ring and pinion in the trans mates to the drive and pinon in the rear diff right? If that is the case then there are three, no?

In the respective United States model 3/S the "3" series differential and "4" series differential are geared differently. Some have said on the other board that a JDM MR geared trans will bolt up to a USDM 5 speed rear diff without burning the VCU which is a "3" series rear differential. If that's the case then what's the gearing in a JDM "4H"

Anyone have pics of "3" and "4" stamped H (hybrid) rear differential drive gear and the mating pinon?

Lastly, anyone have any pictures and info on the rear LSD options for our cars and info wether it be for the U.S. models, Canada, Ausie, JDM, or UK models?

[J. Fast]

OHH, and does anyone know where I can get just the JDM helical locking assembly or have a part number? For clarification, We're looking for an MHI torsion helical lsd that was a JDM option on a 3/S?

[Marty K.]

I have a B3H hybrid rear LSD waiting to be fitted, and my original diff is B4G.(4WS)

My hybrid diff is 2WS

I have no internal pics as yet, but if I do take it apart, I will take some.

Hybrid LSD seems to be only available as an option on Jap GTO's from 1995 onwards. I was available in 2 forms, 2WS and 4WS.

I have checked on CAPS, and the hybrid LSD pineapple is fully interchangeable with the standard item. Only trouble is the cost is silly!
It does mean if you wanted to keep 4WS you could buy a 2WS Hybrid diff and swap the helical part over.

Marty

[GTOJOE]

Correction on above. The 3 series is 2ws the 4 series is 4ws. Remember all JDM diffs have the same ratio regardless of gearbox so all are the same. Internal "pineapple" is identical in both the B3H and the B4H. The outer casing is different to suit Z15A and Z16A chassis.

Hybrid LSD Rear diff? - 3000GT/Stealth International Message Center (http://www.3si.org/forum/f1/hybrid-lsd-rear-diff-441848/)

[GTOJOE]

OHH, and does anyone know where I can get just the JDM helical locking assembly or have a part number? For clarification, We're looking for an MHI torsion helical lsd that was a JDM option on a 3/S?

B3H part #: MR179436
B4H part #: MR179437

Pinapple part #: MR196307 which is the same for both units.

as per GTOX's post here

GTOPerformance.co.nz • Login (http://www.gtoperformance.co.nz/forum//viewtopic.php?f=5&t=1633&p=21381)

[Marty K.]

B3H part #: MR179436
B4H part #: MR179437

Pinapple part #: MR196307 which is the same for both units.

as per GTOX's post here

GTOPerformance.co.nz • Login (http://www.gtoperformance.co.nz/forum//viewtopic.php?f=5&t=1633&p=21381)The Hybrid LSD unit, MR196307 is still available on special order from Mitsubishi, for £2700 sterling!
Also PitroadM have one available, which seems to be the same unit, but I cannot confirm this.

Second hand is really the only way to go.

To find a 2WS hybrid LSD you need to find a 95+ GTO MR that is been broken for parts.
It was only available as an expensive optional extra, so they are quite rare, but there are some out there.

The 4WS hybrid is another thing........in theory it should have been available as an optional extra on 4WS GTO's, but I have yet to find one with one fitted at the factory!

Marty

[IPD]

ratio is the same? then explain why the 5-speed rear doesn't work with the atx, but the 6-speed does.

[stealthTT]

ratio is the same? then explain why the 5-speed rear doesn't work with the atx, but the 6-speed does.


on JDM(also EU) specs, both 5 and 6 speeds gearboxes had the same final gear ratio so that B3H and B4H have the same ratio: 3.545. hope it helped.

dont know about the auto trans.

Ilie

[MR2]

Question: what are the chances that a Diff like that is still intact...considering every Stock viscus is 99% chance expected to be open if i were you Marty I'd be opening it and checking it ASAP.

[IPD]

on JDM(also EU) specs, both 5 and 6 speeds gearboxes had the same final gear ratio so that B3H and B4H have the same ratio: 3.545. hope it helped.

dont know about the auto trans.

Ilie

then it must be JUST the USDM 5-speed that had a diff gear ratio. i can't imagine that they used a different ratio in JDM between n/a & tt.

[GTOX]

To find a 2WS hybrid LSD you need to find a 95+ GTO MR that is been broken for parts.
It was only available as an expensive optional extra, so they are quite rare, but there are some out there.

Just had a gathering here in Aus where one of the cars (99 MR model) had the hybrid lsd, not sure if the owner even knew...

You got pics yeah Mikey?

[GTOJOE]

I first saw the pics of the diff on Luke's facebook and asked who's it was then realized it was Johns which I already had the VIN number for cus of our Cairns meet a few months earlier :p

[GTOJOE]

ratio is the same? then explain why the 5-speed rear doesn't work with the atx, but the 6-speed does.

All JDM GTO M/T had the same rear diff ratio. The Auto was different as the box was not a Getrag box from memory but a Mitsu made one.

[Marty K.]

Question: what are the chances that a Diff like that is still intact...considering every Stock viscus is 99% chance expected to be open if i were you Marty I'd be opening it and checking it ASAP.
Thanks.
I will be inspecting it prior to installation.
I also want to give it a good clean up, and paint job.

A friend of mine has one also, we picked up really cheap. Ebay:-)
Seller obviously didn't know what they had, and it was on a 'buy it now'......

I have checked my viscous LSD a few times, and it still works fine.

Marty

[Marty K.]

Here is mine.
http://i493.photobucket.com/albums/rr291/marty6470/105_5372.jpg
Marty

[Marty K.]

All JDM GTO M/T had the same rear diff ratio. The Auto was different as the box was not a Getrag box from memory but a Mitsu made one.
I can confirm this.....
Ratio is 3.545 for all the manual GTO's, N/A and TT's.
Ratio is 3.307 for the Auto's(which in Japan are 4WD)
Marty

[Emilie@GZP]

as far as US Spec stuff goes with interchanging.... the JDM 6spd transmission uses a US Spec 5spd rear diff. The JDM ATX AWD trans uses a US Spec 6spd rear diff.

[DocWalt]

What exactly is the Hybrid diff? A clutched diff combined with the normal viscous?

[GTOJOE]

What exactly is the Hybrid diff? A clutched diff combined with the normal viscous?


The Hybrid LSD is a combination helical (torsen-type) and viscous LSD. A torsen type diff will have no limited-slip abilities on sheer surfaces like ice. It'll be as useless as an open diff. But the VCU in the hybrid LSD still allows both axles to lock and spin in sync, even on sheer surfaces. On higher traction surfaces like asphalt, it acts like a normal torsen-type diff, biasing torque to the wheel with the most grip.

As per GTOX's post on the NZ forum.

[DocWalt]

Ah, ok. Thanks!

[IPD]

as far as US Spec stuff goes with interchanging.... the JDM 6spd transmission uses a US Spec 5spd rear diff. The JDM ATX AWD trans uses a US Spec 6spd rear diff.

which would make the only "oddball" of the group the USDM 6-speed rear; which is the same part as the atx rear.

[Markingtime]

OHH, and does anyone know where I can get just the JDM helical locking assembly or have a part number? For clarification, We're looking for an MHI torsion helical lsd that was a JDM option on a 3/S?

Don't know if you ever got your answer but I can get you new OEM ones . . . for a price:

I can deliver in about 3 weeks from order with payment:

MR179436 (entire Ralliart 2ws rear diff) - $4394.00*.

MR179437 (entire Ralliart 4ws rear diff) - $4394.00*.

MR196307 (just the Ralliart rear diff pineapple, same for both 2ws &
4ws) - $3412.00*.

*Does not include shipping which I estimate at $200, and requires your 6 speed or auto 3000GT or Stealth transmission to be upgraded to JDM GTO gearing (JDM 6 speed parts are generally available used at reasonable prices, may not be an option for autos. US 5 speeds (I have heard) and gray market RHD JDM GTOs in Canada already have the right gearing).

[MR2]

wow ouch!

[Markingtime]

Yeah, I think they must be some kind platinum alloy.:D

[MR2]

rofl at the people complaining of the cost of the Kaaz :p

wish we had a quieter option that was hybrid though :)

[2fnloud]

The Kaaz is loud?

[MR2]

Reversing/car parking maneuvers + multi-plate clutch bring out the best in it :p

[anyonebutme]

Reversing/car parking maneuvers + multi-plate clutch bring out the best in it :p

Can be tuned out....not everything HAS to be installed exactly like it arrived, lol.

[MR2]

yeah true, been meaning to do that (switch some of the plates to back to back)