The 'ROBlobster Xfer case'


The one thing about the Sierra (sam) i have always thought of as
a short comming, was the overall gear ratios on HI and LOW range.
A standing start with a full load (not to mention with a trailer)
in HI, or climbing a good hill with steps or tree roots across it, in LOW
needed a bit more clutch slip than i like to use.

After looking about on the WEB and in the ORC ( http://www.off-road.com/4x4web/suzuki/ )
suzi list i HAD to have one of those 4:1 low xfer cases.( rocklobster, rockhopper, hawklobster...)
Well here in OZ it would cost me $995 for the gears only and $1495 for
The kit ( not including the case or labour )
I had an offer of the one gear that has to be MADE up for US$300, but
that would still have cost about $1000 all up in my truck.

After a bit of 'playing around' at Suzisport ( Thanx again Graeme ) and hunting the service books
I found where the bits for the 4:1 boxes came from.

Here is a PIC of the gears in the Xfer case:


[Pic1]Input is top right.

Gear "A" is the input gear.
"B and "D" are a one peice cluster.
"B" is the common cluster gear.
"D" is the LOW range gear on the cluster.
"C" is the HI range output gear.
"E" is the LOW range output gear.

I have found 3 sets of ratios for the gears. Also with some ratios
you have the choice of a one or two peice input shaft/gear. The one
in the above case is a two part input shaft/gear.

Peruvian , NZ , Colombia:

Gear A 39 teeth
B 42
C 62
D 24
E 57

Hi range = ( B / A ) * ( C / B ) => 1.590:1
LO range = ( B / A ) * ( E / D ) => 2.557:1


Europe ( and all after june 1983 ):

Gear A 31
B 53
C 49
D 32
E 47

Hi range = ( B / A ) * ( C / B ) => 1.580:1
LO range = ( B / A ) * ( E / D ) => 2.511:1


Most other countries:

Gear A 44
B 41
C 62
D 23
E 56

Hi range = ( B / A ) * ( C / B ) => 1.409:1
LO range = ( B / A ) * ( E / D ) => 2.268:1


So if you have the last xfer and want a little reduction in both
HI and LOW range, you can put one of the last two xfers in.
This is sometimes called a 'baby-rocklobster'. This type of case
comes from an older SJ410 suzuki or from the UTE back stockman/sierra.
1.409 / 1.58 * 100 is about 12.8% reduction.Thats half a gearbox gear lower
OR
Standard 27" tyres with the 1.409:1 gears is the same as 30.5" with the 1.580:1

Thats OK for HI but i NEED a lower LOW !
If we take the A, B and C gears from the 1.580:1 case and the D and E from the
1.409:1 case, and stick them together we would get :

HI range => 1.580:1
LO range = 53 / 31 * 56 / 23 = 4.16:1

I have not seen how other people have done the mod, but
I did not like the idea of a 'Cut-N-Shut' in the middle of
the "B"-"D" counter gears shaft. With a bit of 'discussion' with my
dad and brother, we went with the method shown in the PIC below.


[Pic2]' THE JOIN ! '.
A 41/23 cluster had its 41 teerh ground off and was machined down
to about the diameter of the body of the cluster.
Next the guts of a 53/32 teeth counter shaft was cut out to keep
the 53 tooth gear. The hole in the guts of the 53 gear was left 4 thou
to small at room temp' so at 600-800 Deg C it would 'press' onto the .
stub left on the 41/23 cluster where the 41 tooth gear used to live.
This would have been good enough, but my brother had a weld run over
the join on the outer side.( not seen in the PIC.)

Thanx to:
Brother Rob , dad
Graeme at suzusport
and
CRANKSHAFT ENGINEERING p/l
2/20 Tradelink rd.
Hillcrest Q. 4118
ph. 07 3806 7488
fax 07 3806 7433
Who will do the cut and weld for about $200 if you supply the two clusters.


Here are some things i had not 'thunk' about before installing the 'ROBlobster.

3 rd LOW is now like the old 1st low...This is GOOD.
ONLY one lil' problem..reverse in also verrry low..So if you are trying
to rock and rev' out of a deep bog, you might not have enough wheel
speed in reverse to clean the tread.

There is a fair amount of axle wrap when you plant the foot in 1st low
even with the lower load springs still on.

I also did not know there are at least 2 speedo drive gear sets.
The xfer out of the 410 has a 3:1 reduction to the speedo cable,
where the 413 had a 2.7:1. So when the speedo reads 80 i an doing 100
( With the 215/75s on )

IF the 413 flanges don't not fit (US 1988 --> )onto the 410 case, Drill new
holes in the 410 flanges ( They end up very close to the outer edge of the
flange but none of the torque is side ways) ,also the 413 drive shafts have bigger
centering 'bits' sticking out that have to fit ONTO the
flanges on the xfer case. So i got 3mm (or so) taken out of the flange.

( BUT I STILL LOVE IT ;^)
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