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Jaguar IRS Generations

There are three generations of the venerable Jag independent rear suspensions that have been very popular with Hot Rod/Street Rod and Kit Car enthusiasts and now V8 Bikes since the early 1960s. This is due to their superior handling and ride caracteristics.

The Series I, II and early Series III Jag IRSs are Salisbury units. Not only is it strong, there is some parts inter-changeability with the Jeep Dana 44, posies/limited slips with a large selection of gear ratios.

Late Series II and Series III Jag IRSs have outboard brakes and are Dana units.

Jaguar IRS Models
1961-1975 E-type
1961-1965 Mark X
1963-1968 S-type
1966-1970 420G
1966-1969 420/Daimler Sovereign
1968-1992 XJ6
1968-1992 XJ12
1975-1996 XJS
1986-1994 XJ40*
There was a change in design of the Jaguar IRS after 1985.
The 61-84 unit is in a stamped steel "cage" that is self-contained and easily removed as a single unit.
This makes it relatively easy to adapt to other vehicles.

*The 1986 and later unit uses a subframe/lower wishbone design that is not easily adaptable to other vehicles.

PLEASE NOTE:
I982 and beyond XJ Series uses the 2:88 ratio gear set.
THIS 2:88 CARRIER CANNOT BE CONVERTED TO ANY OTHER RATIO with out an adaptor.
**

SALISBURY VS DANA

Differences between the Salisbury and Dana differentials include:

On the Salisbury, the bearings on the output shafts are held in the case with five bolts. On the Dana, the bearings on the output shafts are held in place with three bolts.

The Salisbury has a drain plug, the Dana has no drain plug.

The input flange on the Salisbury is circular. The input flange on the Dana is rectangular.

Salisbury's inboard brake calipers are bolted to brackets on the flanges holding the output shaft bearings, with the bolts installed from the inboard side outward. (See photo "A" below)
Photo "B" is of the Series I bearing flange on stub axles - XKE and other early models, etc.

Dana's inboard brake calipers are bolted to bosses on the case itself, with the bolts installed from the outboard side inward. In order to access those bolts, the Dana is fitted with brake rotors with access holes.

Jag IRS Specifications

Track Widths see the Generations Chart above for your application.

Model Year Ratios Width
E Type '61-'75 Various *52"
Mark 10 '61-'75 3.54, 3.77 *60.5"
S-Type '63-'68 3.54, 3.77 *55"
420 '66-'68 3.54 55"
420G '66-'70 3.54, 3.77 *60.5"
XJ6 4.2 '68-'85 3.31, 3.54, 3.77 61"
XJ6 2.8 '68-'85 4.09, 4.55 61"
XJ12 '72-'85 3.31 *61"
XJ6/12 '79-'92 2.88, 3.07 61"
XJS '75-'96 2.88, 3.07, 3.54 *61"

* = Factory Locker


XKE, 61-75 (Series I), Dunlap or Girling Calipers, 1/2" Rotors, various Gears w/Locker, 52" wide.
Early series have knock off wheels, later models, 5 lug wheel mounts, GM bolt pattern.

S-Type, 63-68 (Series I), Dunlap or Girling Calipers, 1/2" Rotors, 3.54 or 3.77 Gears w/Locker, 55" wide

420, 66-68 (Series I), Dunlap or Girling Calipers, 1/2" Rotors, 3.54 or 3.77 Gears, 55" wide

XJ6, 69-73 (Series I), Dunlap or Girling Calipers, 1/2" Rotors, 3.54 Gears or 3.77, 61" wide

XJ6, 73-79 (Series II), Girling Calipers, 1/2" Rotors but with odd dust Cover, standard 3.31, 3.54, 3.77 gears, Locker optional, 61" wide

XJ6, 79-88 (Series III), Girling Calipers, 1/2" Rotors, with Drain hole in Stub axle flange, 2.88 Gears, Locker optional, 61" wide

XJ6/XJ40, 88-95, A completely different set up, not recommended for aftermarket applications.

XJS, 76-87, Girling Calipers, 1/2" Rotors, All Powerlock Gears, Tapered Roller Bearings on Stub axles, 3.31 Gears, 61" wide

XJS, 87-89, Girling Calipers, 1/2" Rotors, Flat bottom diff with NO drain plug and 3 bolt mounted stub axles, American Dana Unit with weak traction lock (Not recommended), 2.88 Gears, 61" wide

XJS, 89-95, Girling Calipers, 1/2" Rotors, ABS on uprights, speedo pickup in rear aluminum diff cover, 2.88 Gears, 61" wide

There are 3 different types of stub axle flanges/caliper mounts. Series 1 & early II, pic "B", and 2 later Series II with additional bolt tabs for the calipers, pic "A," the other where the bearing is oiled thu the cap . The differences are due to bearing configurations - ball bearings vs tapered roller bearings.

Also, the Series I case has fins in the casting along the side of the pinion area.
The Series II casting has a solid wide bars.


Again, PLEASE NOTE:
I984 and beyond XJ Series uses the 2:88 ratio gear set.
THIS 2:88 CARRIER CANNOT BE CONVERTED TO ANY OTHER RATIO without an adaptor.
**


Series I Bearing Cap (flat)
w/o Caliper Flange
Series II Bearing Cap
w/Caliper Flange

To recap the Series I and Series II differences...
The Series I casting has 4 fins around the pinion area.
The Series II casting has solid wide bars along the pinion area.

The Series II bearing retainer cap has a flange for the caliper mount.
The Series I bearing retainer cap is flat and has no flange. The caliper is mounted with two small brackets.
The Series II has tapered roller bearings on the stub axles.
The Series I has ball bearings on the stub axles.
They use different front-mounted calipers.

Stub Axle Bearing Identification
XJ6/XJ12, 69-73 (Series I) Ball Bearing on Stub Axles
S-Type, 63-'68 (Series II) Tapered roller Bearings on Stub Axles
XJ6/XJ12, 73-79 (Series II) with Odd dust Cover Tapered roller bearings on Stub axles
XJ6/XJ12, 79-88 (Series III) Tapered roller bearings on stub axles
with a drain hole in the stub axle bearing cap for bearing oiling
XJ6/XJ40, 88-95 - A completely different set up, not recommended for aftermarket applications
XJS, 76-87 Tapered Roller Bearings on Stub axles

Again, PLEASE NOTE:
I984 and beyond XJ Series uses the 2:88 ratio gear set.
THIS 2:88 CARRIER CANNOT BE CONVERTED TO ANY OTHER RATIO with out an adaptor.
**


** WE HAVE THE ADAPTORS AVAILABLE - CALL US FOR INFORMATION
Can only be used with 2:88, 2:92, 3:07 to 3:76 gears.