What height to mount a Jag IRS

[fatfendr]

I'm stuck and am hoping for some advice. Decided to start on the rear end of the Dodge. I'm going to solid mount the Jag rear, but leave it caged. How do I determine what height in the chassis rails I should mount it. The Jag coils are pretty stiff, so I took them out for ease of setup.

I know the drive shafts are supposed to be horizontal, but how do I set it up for that when there is no weight on the chassis and don't know how much it will weigh when finished. Obviously I don't set them up horizontal no, otherwise with weight they will be pointing downward. How critical is the rear end height location, or do I just mount it and compensate with aftermarket coils when all the weight is in the car ?

John

[PeterR]

I'm stuck and am hoping for some advice. Decided to start on the rear end of the Dodge. I'm going to solid mount the Jag rear, but leave it caged. How do I determine what height in the chassis rails I should mount it. The Jag coils are pretty stiff, so I took them out for ease of setup.

Make up the jig as shown here and leave it in place until you have finished, then start tweaking the springs.

http://www.ozrodders.com/forum/viewtopi ... &hilit=jig

In particular,

The spacer made from 5/16 diam rod as shown will do the job, but being rather whippy it can not sustain much compression without buckling. If you make a more rigid spacer jig then it can be bolted to the mount hole and secured over the fulcrum nut then remain in place right through the vehicle construction and ensure ride height will be maintained even if the springs are taken out.

It can easily be fabricated from a piece of 20mmx20mm or 25mmx25mm RHS 150mm long with a flat tab welded to each end, or a piece of suitable angle section 250mm long with a 50mm notch cut off opposite legs at each end to form the tabs.

[FRANK BASILE]

The angle of the side shafts at normal ride height is not exactly parallel to the ground either at normal kerb weight.
Somewhere I had the shocker eye to eye measurements I took from a number of Jags to simply get a typical setting. to replicate into my final loading calculations
If you get hold of a service manual there is a check tool mentioned also .
I can enquire today or tonight, my son works on these vehicles all day.
Frank.

[PeterR]

The angle of the side shafts at normal ride height is not exactly parallel to the ground either at normal kerb weight.
Somewhere I had the shocker eye to eye measurements I took from a number of Jags to simply get a typical setting. to replicate into my final loading calculations
If you get hold of a service manual there is a check tool mentioned also .
I can enquire today or tonight, my son works on these vehicles all day.
Frank.

Pictures of the tool and the measurements are in the link above.

[fatfendr]

Hmmm, ok I better go and decide what ride height I want the chassis at. Maybe I need to drop the body back on. That sux a bit. I'll then make a jig for where the shocks mount, making sure I have the 218mm measurement between the fulcrum shaft and lower V mount. The jig at the shocks should be easier for me as I'm not using the V mount. Interesting comment about making the inner fulcrum level and not worrying about the angle of the pinion flange.

That front end measurement should be handy too. The front, rear and engine were all from the donor Jag. I guess if I have the mid laden measurements correct and use existing engine mount, I shouldn't have to worry about drive angles as it will be identical to the vehicle it came out of.

This may have just helped me out further down the track.

John

[jeffa]

Rather than drop the body on, what about similar weights? Might be easier.

[CarGuys]

Confusing looking post, The inner and outer pivots on the lower arm should be 61mm higher on the centre ones at ride height.

The cage is mounted to the diff housing and so are the lower control arms, so the shocker install height has nothing to do with the set up when mounting the cage to the frame.

If the top of cage is mounted level to the ground at ride height the pinion angle should be similar to the factory spec.

Drive shaft angle will have to be adjusted when you set the engine and transmission in the car, to provide proper universial joint function.

I have a question for you, Why haven't you taken the time to at least wash all the crap of everything before you start thinking about fabrication or set up?

Advise clean all the stuff, grind all the areas to bright steel where ever you even think you might have to weld. Dirt and rust dont weld.

The old saying applies: Poor preparations leads to Poor results.

Mark Shearer

[mgtstumpy]

I use the 4 x OEM rear Jag coilovers on my 35 Chevy tourer and it rides a treat and it'd weight considerably less than your body. Once you add the body weight you'd be surprised how much it will settle to achieve ride height. Plus that IRS is a LOT of unsprung weight. I removed the cage in my installation so there was a lot more fabrication and measuring etc. I wouldn't mount by filling the gap as per templates, is it being solid or rubber mounted? Filling gap that way in my view (cantilever style) adds additional stress to chassis when under load. If rubber mounting in OEM cage I would widen it and cut the OEM housing ends off and make flat filler piece to spread the load and fold it to match the cage profile and overlap cage where it joins. The ends that the mounts attach to could be welded back on to accept OEM mounts if that's what you want. Weld along the seam when it joins plus add a few plug welds as well to ensure rigidity and integrity of structure.
Also when mounting, make sure that the diagonals are right to ensure it is square in the frame and that when at ride height, the tyres are centred in the rear mudguards. Nothing looks worse to me than a rear end mounted incorrectly and biased either to the front or rear. Might not bother some people but that's me.

[madmike3434]

couple of things that people are not discussing re the 1960 thru 1986 jag IRS. The pinion angle is predetermined by the side lower control mounting arms. These are the cast arms that bolt to the center section with the 2 ......1/2" coarse thread special GRADE 9 bolts are available from concours west industries These should also be saftey wired as its critical these do not back off. The 4 bolts on top of the jag should also be safety wired in pairs. Also some loctite RED should be used.

The lower control arm mounting side brackets , depending on the year could be any of the following pinion angle degrees 0----3---6. These arms determine what degree the pinion is. With the rear end sitting flat on the ground put an angle degree tool on the pinion mount or top mount and read what it says. The jag rear end should sit flat and level with the ground.

A jaguar rear end is totallly independant. An older vette style is not. When you grab hold of the hub carrier without the shocks attached, notice that the hub carrier flange plate with wheel studs , when it moves up and down thru the motion, notice that the hub flange always remains on the same plane , never in an arc. A corvette rear arcs and swings towards the body.

Its important also to make sure that a good 3/4 inch round sway bar be installed, front end and rear end to prevent the body from tilting inward as you go around a corner or the body will be rubbing on the tire. There is not a lot of room in most older car wheel wells in the rear.

Note also that there are two types of jag shocks.....one with 10 coils from sedans and one with 8 coils, these are usually from XKE models. An under 3000 pound car can use the E type shocks and a heavier vehicle will need the 10 coils shocks otherwise it will bottom out.

jag shocks center to center of mounting rod holes is 13 inches. Maximum rebound of the shocks is 3 inches.
Take the measurements of the factory cage for where the shocks mount in relation to the center of the jag center section, these are the best settings for the correct angle to mount your shocks. Do yourself a favor and get the jag rear out of the cage and it will be a lot easier to work on.

STREET RODDER MAGAZINE ran a whole jag rear identification article 4 issues about everything you were afraid & wanted to know in the 90's .
Also discuses how to narrow a jag rear end as they come in 3 widths from 53--62" wide

MGTSTUMPY also has the correct info

mike

[madmike3434]

I have asked mark taylor ( mgtstumpy ) to post 3 pictures of my jag install in my 1935 chevrolet standard series ,to this thread.

The mounting crossmember as you will be able to see is 1/4 " thick wall 2" x 3 " tube The jag rear is mounted with urethane bushings in red to reduce vibrations. The shock mounting angle is almost stock jag. But for extreme flexibility for ride height adjustablility, inside the crossmember is a piece of 1/4' thick metal that is tapped for FOUR 5/16 bolts. This plate slides along INSIDE the crossmember thru 2 slots ============= like this that are cut into the crossmember underneathe. It allows you to raise or lower the rear ride height by as much as 5 inches simply by looosening the 4 bolts and sliding the shock mounting brackets OUTWARDS.

CONCOURS WEST INDUSTRIES in Oregon USA makes this.

Last tips.......if you take the jag out of the cage, make sure you keep the bottom plate attached as that keeps the whole bottom bracketry strong. Also as a point of interest the half shafts use 1955---1964 chevy 1/2 ton truck universal joints .

Concours west industries and kugel components in california make white urethane 2 piece bushings to replace the 4 wheel ball bearings in the lower control arms , plus also the hub carriers. They also make a bushing set to replace the side rubber mount that is used as a track bar on each side.

mike

[mgtstumpy]

Here goes, Mike's 35 Fisher bodied coupe



I set my chassis up at required rake and with body on and wheels attached to rear end and rolled it in to ensure it was positioned correctly. I was also reminded and forgot, if you remove unit from cage you definitely need that bottom bash plate and tie bars front and rear as well as torque roads on front to stop pinion wind up up on acceleration and wind down during braking. A lot of load on the those 4 attaching bolts on top of diff otherwise. Bash plate bolts to lower castings that bolt to diff centre as the lower control arms pivot of them. Ties them together as suspension works through its arcs and strengthens everything. Otherwise all load is placed on the four (4) attaching bolts on the castings. NOT GOOD. This is mine without body on and off. Note that in Mike's coupe like mine, the 1/2 shafts are not parallel to the ground when at rest with body on. Also he rubber mounted (Isolated) his centre. Mine is solid mounted. You want the tyre centred in rear wheel arch for car to look right

[fatfendr]

Ok, back from the shed and have done some measuring and more thinking. I followed PeterR's advice and made a jig for the rear end height. The 218mm measurement from the links he referred to, equates to 280mm from top shock mount to bottom shock mount (give or take a couple of mm). I used some 20mm x 20mm box steel as these spacers and mounted them where the shocks were. one on each side. Drive shafts sitting close to level with the ground now. Measured standard shocks and at full extension they are 340mm. Can't compress them to see length at full compression, but was just going to do this out of curiosity to see if this mid laden height was close to the middle of the shock travel range.

Checked the angle of the inner flange / control arms. How do you put a level on them when they are that shape? I measured from the ground to the nut at the front and the same to the nut at the back. 200mm both measurements. With them level I checked the pinion angle and sure enough it was 0 degrees. Just a comment...although top of cage is level, gauge on top of diff bolts shows a decline of 6 degrees toward the front.

Anyway, decided not to drop the body back on to get an idea of finished chassis height. Instead I setup the rear guard to how I wanted it to sit over the rear wheel. Knowing where the body sits on the cahssis and where the guard mounts to the body, I took some measurements and was able to determine a fairly accurate idea of where the chassis has to sit off the ground. Knowing this and knowing the IRS mid laden heght as determined by Jag, I think I know know at what height my IRS has to sit in relation to me chassis.

For this, I thank those who have offered advice.

Now to address some other comments/questions etc.

The IRS although staying in the cage, was still going to be removable, so no need to worry about me welding in a filthy IRS and then trying to clean up a cage in situ. And I'll be detailing it when I strip it down, before putting it back in.

I know there are numerous perceived right and wrong ways to do things, but I wouldn't have thought my mounting intention was not that bad. The cardboard template was not a finished and complete arrangement. There was more to my mounting brackets. As far as cantilevar and strength goes, there was going to be 6 M14 bolts each side holding the "cardboard template" to a 8mm vertical spacer plate between the chassis and this "cardboard template". The "cardboard template" was to use the standard JAG V-mount bolts of which there are 6 each side holding it to the cage. Probably hard to understand or picture...sorry.

Anyway, guess what? I'm now thinking of going back to my original thought of rubber mounting the cage using the standard v-mounts. That might get me some more acceptance....from some. I did original want to do this, but due to the Dodge's wide chassis, solid mounting looked like a much easier option.

Looks like I'm going to have to narrow the cage by about 10mm each side and then have a parrallel piece of 75x75 that the v-mounts will bolt to and will attach to the inside of the cahssis, allowing for a 10mm gap for the v-mount nuts. Hmmmm sounds like fun. Maybe I should have kept the 9" after all.

Hopefully I can post some photos after I spend the day in the shed on Friday.

Hey Mike...nice rear end. Why didn't you mount your lower trailing arms in line with the inner fulcrum pivots. You're going to get your knuckles wrapped.

John

[madmike3434]

Its not necessary to mount the trailing arm ( side track bars) to any pivot point......look at the STOCK JAG ARMS they are just mounted straight ahead. This is the way kugel komponents and concours west industries also does theirs . The movement of the rear hub carrier is only 3 inches maximum with the stock shocks. The trailing arms do only two things, stop the lower control arms from moving forwards or backwards under acceleration or deceleration. They also control the no arc up and down hub carriers.

Re the side lower control arm brackets......when you set the rear flat on the ground and place an angle finder on the pinion, that tells you exactly what pinion degree you have....0--3--6 . That is determined by the side brackets. The jag is to be mounted so that the lower control arms and the hub carriers move straight up and down in a 90 degree arc .

As mentioned before you should consider a 3/4" thick sway bar to counteract body roll.

mike

[jeffa]

Delayed response, but I just made some measurements on the Jag RE I have at the moment.

I set it up on a reasonably level surface, then used jacks, blocks of wood, wedges etc to set the top surface of the cage level in both directions.

Then I set up a square on the floor, supported in such a way so I could adjust it to be perpendicular to the cage top surface (using another level).

I set this assembly next to a wheel stud, and when I lifted the hub up and down through it's travel, the hub moved exactly vertical when viewed from the side.

Then I used the square to check the pinion angle - dead vertical to the top (level) surface of the cage. Not quite what I expected.

I read around the traps, that to mount these, you set the top surface of the cage level to the road. This makes sense to me, as the wheels will then travel perpendicular to the road surface over bumps etc.

But then there'd be no pinion angle. I don't think Jag engines are mounted level are they?

Conversely, there is a pressing in the top surface of the cage. Maybe the experts mean mount the cage with this pressing level? That would give a healthy pinion angle, but now the wheels wont travel perpendicular to the road surface.

[krusty]

Ok, back from the shed and have done some measuring and more thinking. I followed PeterR's advice and made a jig for the rear end height. The 218mm measurement from the links he referred to, equates to 280mm from top shock mount to bottom shock mount (give or take a couple of mm). I used some 20mm x 20mm box steel as these spacers and mounted them where the shocks were. one on each side. Drive shafts sitting close to level with the ground now. Measured standard shocks and at full extension they are 340mm. Can't compress them to see length at full compression, but was just going to do this out of curiosity to see if this mid laden height was close to the middle of the shock travel range.

Checked the angle of the inner flange / control arms. How do you put a level on them when they are that shape? I measured from the ground to the nut at the front and the same to the nut at the back. 200mm both measurements. With them level I checked the pinion angle and sure enough it was 0 degrees. Just a comment...although top of cage is level, gauge on top of diff bolts shows a decline of 6 degrees toward the front.

Anyway, decided not to drop the body back on to get an idea of finished chassis height. Instead I setup the rear guard to how I wanted it to sit over the rear wheel. Knowing where the body sits on the cahssis and where the guard mounts to the body, I took some measurements and was able to determine a fairly accurate idea of where the chassis has to sit off the ground. Knowing this and knowing the IRS mid laden heght as determined by Jag, I think I know know at what height my IRS has to sit in relation to me chassis.

For this, I thank those who have offered advice.

Now to address some other comments/questions etc.

The IRS although staying in the cage, was still going to be removable, so no need to worry about me welding in a filthy IRS and then trying to clean up a cage in situ. And I'll be detailing it when I strip it down, before putting it back in.

I know there are numerous perceived right and wrong ways to do things, but I wouldn't have thought my mounting intention was not that bad. The cardboard template was not a finished and complete arrangement. There was more to my mounting brackets. As far as cantilevar and strength goes, there was going to be 6 M14 bolts each side holding the "cardboard template" to a 8mm vertical spacer plate between the chassis and this "cardboard template". The "cardboard template" was to use the standard JAG V-mount bolts of which there are 6 each side holding it to the cage. Probably hard to understand or picture...sorry.

Anyway, guess what? I'm now thinking of going back to my original thought of rubber mounting the cage using the standard v-mounts. That might get me some more acceptance....from some. I did original want to do this, but due to the Dodge's wide chassis, solid mounting looked like a much easier option.

Looks like I'm going to have to narrow the cage by about 10mm each side and then have a parrallel piece of 75x75 that the v-mounts will bolt to and will attach to the inside of the cahssis, allowing for a 10mm gap for the v-mount nuts. Hmmmm sounds like fun. Maybe I should have kept the 9" after all.

Hopefully I can post some photos after I spend the day in the shed on Friday.

Hey Mike...nice rear end. Why didn't you mount your lower trailing arms in line with the inner fulcrum pivots. You're going to get your knuckles wrapped.

John

you got 75mm travel on your jag coil overs