The Gearbox & Diff thread

[Dras]

I also have a V7A6 box. Will see what ASA has to say about the VIN tonight.

I found this on the http://www.mivec.co.nz.

Gearbox Code________Part #___________Years Available
F5M42-2-V7A1________MD974040________94-95
F5M42-2-V7A2(LSD)___MD974041________94-95
F5M42-2-V7A3________MD974602________95-2000
F5M42-2-V7A4(LSD)___MD974603________ 95-97
F5M42-2-V7A6(LSD)___MD975854_________97-2000

[Bennoz]

Ahh, nice.

You see Im also thinking the helical diff came out in the later model boxes (V7A6's) where as the earlier types were the viscous...

[Dras]

Ok, the VIN of the FTO my V7A6 box come out of is DE3A-0301329.

According to ASA, this was a GP Version-R2 (1999). The part number for the diff is MD770978.

[Shane001]

Might be worth adding VIN numbers as well where available, can then cross reference on CAPS

DOH posted this in reply to the first page...

[Bennoz]

Anyone else? Anyone with a Version R that would be happy to share vin & or gearbox numbers?

[aza013]

I will have a look for you.

Edit:- ok numbers are F5M422V7A6........... VK3480..

[Bennoz]

Which... I reckon.... means you got the helical LSD

[aza013]

So I take it that is a good thing?
The only thing I know is it works well.

[Kustom]

[Vectose]

Just had a look at mine

F5M422V7A6 - VJ3055

[Rob Furniss]

Just had a look at my old 4spd tip GPX on ASA and it turns out it had LSD - PNC 27690A but no part no data.

[Bennoz]

Just rebuilding another box with limo diff

F5M42-2-V7A2(LSD)___MD974041________94-95

Its a viscous type

[Bennoz]

Just *popped* another box open, F5M42-2-V7A2... and guess what? Viscous LSD.

So I think we've established the V7A2 are viscous LSD, the V7A6 is the helical type.

Also, some points to note:

The Viscous LSD uses different bearings to the standard & helical diffs. The centre bore is smaller.



It's also the the diff (viscous) that uses the stubby ended drivers side driveshaft. (Yet you can still see straight through the centre of the diff.)

[Taz]

You want me to check my 98 model diff there Ben? Or have you establisged what you wanted to know?

[Shane001]

So Ben to clarify, can you see straight through both the Viscous & the Helical LSD's?

And when you say Viscous you're referring to a clutch based LSD & Helical as a torsen type LSD?

Any chance you could put some side by side pics up of different angles? I'll email you a few pics I've taken of the diffs I've had apart to post up as well.

[Bennoz]

Yes can see through both. If you've gone to the trouble of popping driveshafts to check, the only way to determine Helical vs Viscous (apart from the numbers stamped on the box (F5M42-2-V7A2 vs F5M42-2-V7A6) is that the viscous type uses the stubby ended drivers side shaft.

Yes by helical I mean torsen style, but I wouldn't consider the viscous a clutch type, its more like a viscous coupling on a fan. Its got all these thin wafers that spin around in a specific viscosity goo in the centre of the diff in a sealed section. The goo also changes viscosity with temperature.

I'll get some pics of that up with your ones too.

[clint111]

Mine is 2V7A2 AA3749
From a 95 something.
Half cut, so I have a viscous lsd?
Woot! I have LSD!

[Shhtuart]

My 1998 GPvR 5spd Tip is F5A42 1E7A1 GM839

Viscous?

[aza013]

I hope this helps .

Links to pics of the helical dif.
http://www.google.com.au/search?q=helic ... 24&bih=672

Torque sensitivity
This category includes helical gear limited-slip differentials and clutch, cone (an alternative type of clutch) where the engagement force of the clutch is a function of the input torque applied to the differential (as the engine applies more torque the clutches grip harder and Trq d increases).
Torque sensing LSDs respond to driveshaft torque, so that the more driveshaft input torque present, the harder the clutches, cones or gears are pressed together, and thus the more closely the drive wheels are coupled to each other. Some include spring loading to provide some small torque so that with little or no input torque (trailing throttle/gearbox in neutral/main clutch depressed) the drive wheels are minimally coupled. The amount of preload (hence static coupling) on the clutches or cones are affected by the general condition (wear) and by how tightly they are loaded.

And the viscous.

http://www.google.com.au/search?q=visco ... d=0CGEQsAQ

Some info to have a read of .
Viscous

The viscous type is generally simpler because it relies on hydrodynamic friction from fluids with high viscosity. Silicone-based oils are often used. Here, a cylindrical chamber of fluid filled with a stack of perforated discs rotates with the normal motion of the output shafts. The inside surface of the chamber is coupled to one of the driveshafts, and the outside coupled to the differential carrier. Half of the discs are connected to the inner, the other half to the outer, alternating inner/outer in the stack. Differential motion forces the interleaved discs to move through the fluid against each other. In some viscous couplings when speed is maintained the fluid will accumulate heat due to friction. This heat will cause the fluid to expand, and expand the coupler causing the discs to be pulled together resulting in a non-viscous plate to plate friction and a dramatic drop in speed difference. This is known as the hump phenomenon and it allows the side of the coupler to gently lock. In contrast to the mechanical type, the limiting action is much softer and more proportional to the slip, and so is easier to cope with for the average driver. New Process Gear used a viscous coupling of the Ferguson style in several of their transfer cases including those used in the AMC Eagle.
Viscous LSDs are less efficient than mechanical types, that is, they "lose" some power. In particular, any sustained load which overheats the silicone results in sudden permanent loss of the differential effect.[7] They do have the virtue of failing gracefully, reverting to semi-open differential behavior. Typically a visco-differential that has covered 60,000 miles (97,000 km) or more will be functioning largely as an open differential;[citation needed] this is a known weakness of the original Mazda MX-5 (a.k.a. Miata) sports car. The silicone oil is factory sealed in a separate chamber from the gear oil surrounding the rest of the differential. This is not serviceable and when the differential's behavior deteriorates, the VLSD center is replaced.

[wagonist]

Seems like an LSD is quite a common option for the FTO. Is this correct?
And how hard to find?

Is there any way to find out how different the FTO box is to the US spec Eclipse? Quaife sell brand new Torsen/Helical diffs for both the V6 FWD & front diff of the AWD turbo.
Some bright spark figured out that the latter one (ie front diff of the AWD box) fits the Hyundai Elantra box (which I've now fitted to my Excel).

I've still got the factory open diff of the Elantra at home to take some measurements if that'd help.