Looking for your thoughts on the strength of the Jag IRS. I believe
the dana 44 diff set-up should be good for 450 + hp/tq
applications. My questions leans more towards the stub axles and
wheel hubs. If I am correct, these are a 19 spline unit? I have
already had an experience with a wheel stud spinning in the wheel
flange and I would like to look at changing that design to a longer
screw in stud, but I really don’t want to put all that work into a
19 spline hub, that I view as a weak point. Did Jaguar make
anything else that may handle a little more abuse. I am looking at
a drag racing application. Thanks.
In reply to a message from Rob Wade sent Sun 14 Nov 2010:
Well the 427 Ford Cobra used that same set up… regularly I used to
see 550HP engines back when 550 hp was the biggest dog in town…
Rob Beere Racing makes 780 horsepower and races that same rear end
set up…(wins regularly against much newer machinery)
The only mod I did with my racing V12 XK-E was to mill off the stub
axle where the nut holds everything in place and replace it with
with a NAS bolt of 1 inch diameter…
The V12 can easily make 650 HP and more if you’re willing to
spend the money…
Drag racing isn’t about loading though… you tend to shock
things… You’ll find that with IRS you can’t hook up as well as
with the old fashioned straight axle. It’s a matter of
geometery.That plus NO Jaguar I can think of has enough room in
it’s fenderwells to take much of a slick…–
MGuar
Wayzata Minnesota, United States
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In reply to a message from Rob Wade sent Sun 14 Nov 2010:
never had any problems with the Salisbury or dana center with 6
liter engines with up to 460 lbs/ft of torque but that all changed
when we put a 460CI V12 with 578 lbs.ft of torque in a XJ-S.
started beaking axle stubs, replaced with C5 corvette ones, then
axle shafts, replaced with tubular ones. broke jaguar 4 speed
gearbox, replaced with Viper T56. then finally the diff, replaced
with 9in.
wheel hubs are 10 spline and would be the weak link for drag racing
with engines over 500 lb/ft torque.
It’s torque that breaks things not HP.–
The original message included these comments:
the dana 44 diff set-up should be good for 450 + hp/tq
wheel hubs. If I am correct, these are a 19 spline unit? I have
In reply to a message from Norman LUTZ sent Mon 15 Nov 2010:
What was involved in the corvette stub axle swap? I understand a
corvette style halfshaft, but you would be talking spider gears,
stub axles and what kind of fab work to adapt them?–
Rob Wade
Windsor Ontario, Canada
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In reply to a message from Rob Wade sent Mon 15 Nov 2010:
Now that I think about it…how did you use the corvette stub
axles (outboard brakes) on the jag diff with inboard brakes?–
Rob Wade
Windsor Ontario, Canada
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Rob there was a company called Concours West Industries that had really
heavy duty Jaguar IRS components. I think they did a lot of work with Cobras
and high power applications. From memory, I believe they were in Washington
or somewhere on the west coast. I don’t see any hits for their website any
more so they might be out of business but perhaps someone else on the list
will know more.
In reply to a message from Rob Wade sent Mon 15 Nov 2010:
You can put outboard brakes on the Jag hubs by using the XJ40 rear
Hubs. It’s a pretty simple swap for racing… I don’t use the
parking brakes on a race car so that’s not anything I’ve looked
into…
It’s nice to get the brakes away from the diff… brake temps can
be over 1400 degrees in racing applications which will quickly cook
diff oil.
Better off having them outboard. Diff doesn’t need an oil cooler
then untill over 500 Ft.pounds of torque… (above 400ft. pounds I
use the aluminum finned cover to help cool the diff.)that and some
cooling air. Don’t pick it up from underneath… already plenty hot
from the engine… better off with a NACA duct off the body work,
Right at the fender flare works well since that’s a high pressure
area… Once you put air into the area give it a way to get back out
or it will stagnant and remain hot…
Best trick is to put it out right at the rear license plate area.
Does several things… first provides fill air in an area that is
normally turbulant. Second there is a real extraction effect
sucking air out from the area… third reduces drag because of the
provided fill air…
You can also use that same area to pick up hot air at the fire
wall and through ductwork put it out at the rear of the car…
Dramatic reduction in under hood temps. Further reduction in
drag… Coolers can be moved to the trunk to shift weight to the
rear.
Won’t work at all on street cars…
Road race applications are easier on the diff than drag racing…
since you’re talking about loads rather than shock…–
MGuar
Wayzata Minnesota, United States
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In reply to a message from Norman LUTZ sent Mon 15 Nov 2010:
I used a synthetic oil for the diff. found out diff temps dropped
by over 100 degrees…
That and move the brakes outboard using XJ40 hubs. Improved
airflow around the diff kept things alive under a lot more load…
Brake temps can be 1500 degrees in racing aps. moving them
outboard drops temps significantly…
air flow around the diff drops temps as well.
Can’t pick up from underneath… already heated air… use NACA
ducts. Side windows or in front of the rear wheel flairs.
However the real trick is to provide air a way out… dump it out
in the license plate cut out… does a bunch of nice things…
Provides fill air in an area that is normally turbulant. Thus
reduces drag. (and provides a extraction effect) With the
reduction in turbulance any downforce measures used will be much
more effective (Spoiler, wing).
Can also duct hot air from firewall area to rear to dramatically
reduce underhood temps… while you’re at it put cooler back there
to shift a little weight aft… (Heavy V12)–
MGuar
Wayzata Minnesota, United States
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If I remember correctly, Concours West had a very heavy duty swap
that used a Ford 9" aluminum pumpkin. I can’t seem to bring up their
website this morning, but maybe it will be up later in the day: http://www.cwiinc.com/www.cwiinc.com
In reply to a message from Mike Frank sent Tue 16 Nov 2010:
I talked with Boost Logic here in Austin tx.
they put over 1000hp around 800tq, regularly thru the CWI
,IRS. (bring lot of money)
its mounted in Toyota supras.
they did say the 93-97 supra IRS would handle 750hp, 600tq
no problem.
and they are a much less expense, also the IRS in 93-98
Toyota
SC 400 are very strong.
check things out around your part of country, uno japanese
dont make no junk–
The original message included these comments:
In reply to a message from Ronbros sent Tue 16 Nov 2010:
Here’s a street rod I just built headers and exhaust for last
month. It has the 9’’ ford based irs in it…huge money! I
would put a solid axle in it long before I would think about
spending that kind of money. The TPI motor is no where near making
enough power to break the dana 44, but if I stuck the car good with
a little spray, I could see it breaking a stub axle.
In reply to a message from Rob Wade sent Tue 16 Nov 2010:
right on ROB, hard to justify that kind of rear, in that type
car, Dana 44 more than adaquate, or whole JAG setup.
just mentioned Toyota rears, probably showin up in junk yards
now, I bought one for $400, bucks ,had to take it out tho the
whole thing.
back a few yrs I had a deal at local yard Jag rears for $100.
US.–
The original message included these comments:
month. It has the 9’’ ford based irs in it…huge money! I
enough power to break the dana 44, but if I stuck the car good with
a little spray, I could see it breaking a stub axle.
In reply to a message from Ronbros sent Wed 17 Nov 2010:
Had a local guy build himself a nissan 240 (newer) with the JZ2
engine and a MASSIVE turbo! Was making the better part of 850 and
running a supra trans and rear diff. 9.90’s at 143…no
breakage…granning shifting the car. Defenately strong pieces.–
Rob Wade
Windsor Ontario, Canada
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In reply to a message from Rob Wade sent Wed 17 Nov 2010:
All of this assumes Drag Racing application…Jaguars drag racing?
Sort of like wearing a Too-too for hockey practice. Not illegal but
sure silly.
Road racing dosn’t have standing starts! Corner loading is far
higher than acceleration loading… The race is never conducted in
1st gear anyplace on the track most starts are at around 50-90
MPH. Darn few second gear corners either…–
MGuar
Wayzata Minnesota, United States
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In reply to a message from MGuar sent Sat 5 Mar 2011:
true MG, what are you sayin.
Jag IRS never was good for Drag racing, we figured that out
back in the 60s, my 57 Corvette out acclerated many XKEs.
never had one get me on top speed ethier!
youno kid stuff, street racing stop light to stop light,
we had a lot of fun and then back at the coffee shop told of
our tales.–
The original message included these comments:
All of this assumes Drag Racing application…Jaguars drag racing?
Road racing dosn’t have standing starts! Corner loading is far
higher than acceleration loading… The race is never conducted in
1st gear anyplace on the track most starts are at around 50-90
MPH. Darn few second gear corners either…
I have dragrace with the same Jag rearend since 2004 it has 3:31 and workes amazing well.
Car is a T23 Hotrod with 607HP Chevrolet smallblock. best ET. 60ft 1,44 1/8 6.13/180km/h and 9,69/234km/h. This summer i tried to drive it on track to use the steeringwheel litle more
Best ET on Gelleråsen 1min 25 sec . I would like som ideas to perform the Jaguar rearaxle for better performance on track. should i get any new bushings in better material? Best regads Johan
Johan a good drag car , has enough grip to lift the front tires off ground!
that comes down to good drag tires, that when track is prepped you cant spin them!
torque at the tire is done with a low gear ratio(hi number), i’m guessin you could use a 4.11-1 ratio(or4.56).
1st gear and ratio should be in the 13/15-1 total ratio!
what transmission you using? whats 1st gear ratio dose it have?
most drag races are done in the 1st 200ft, or if you have plenty of top end power you may have a fast speed , but low ET.
ron
