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Rambler with Jag IRS, Take 2!!

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farna View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Topic: Rambler with Jag IRS, Take 2!!
    Posted: Jun/23/2016 at 9:28pm
Well, I broke my IRS. Not the actual unit, but the mount. I thought I bent the crossmember, but what happened is it broke at a weld. Pics below. If I'd used 1/4" plate instead of 1/8" it would have probably held up just fine forever.





I made a hard left turn out of a side road when this happened. The combination of engine torque and the right tire gripping hard and pushing at the bottom finally ripped the weld. It's been under there for 13 years and about 50K miles, so I'm not terribly disappointed.

The crossmember was bolted straight to the rear suspension sills ("frame rails"). This allowed a lot of vibration to be transmitted into the car body. I needed to pull this out and rubber mount the crossmember anyway, and was planning on doing it this summer. Well, now no excuses, someting HAS to be done!!


Edited by farna - Jun/23/2016 at 9:45pm
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jun/23/2016 at 9:38pm
I had figured out how to add rubber mounts. I was going to shorten the crossmember slightly on each end (about 1/4" each end) then extend it underneath between the shocks under the rails. Then use Jeep six cylinder motor mounts between the extensions and body. Why Jeep? Because they have pieces that prevent the motor mounts from pulling loose if the rubber should part. Handy when off four wheeling, and would keep the rear axle from coming out from under the car in my case.

I took a different direction though. I decided to get a Jaguar "cage" and mount it under the car. The Jag IRS was designed back in the late 50s and first used in 1961. It was made to replace the live axle in current production Jags with no change to the frame. So it drops right in with some added holes and boxing  where the mounts bolt on.

Here's a pic of the cage and mounts out of the car.








Edited by farna - Jun/23/2016 at 9:47pm
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LakesideRamblin Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2016 at 1:15am
Bummer it broke but you got your mileage worth. Cool fix with the Jag IRS. Be interested to hear what you think about how much it lessens the vibration compared to pre-rubber installation.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2016 at 5:20am
Not knowing anything about how your rear section underbody and the Jag IRS cradle mount attachment... from the pix, of the attachment brackets for the cradle, seems if you can fab a replacement bracket that will adapt to your existing frame to mount the cradle in place. As long as there is room underneath.

It would be a cleaner look and puts the reinforcement in the custom mounts not the welds.

Though 1/4" plate is pretty thick stuff, my rack and pinion mounts I custom made are thicker than any part of the car's frame including the crossmember, but is definitely not 1/4" thick.

Have not measured the thickness of steel, but it must be an in between thickness, as I cut square steel tubing.

One thing about smaller wheel based and light weight cars... an IRS suspension really makes a difference when properly done.

For those who have long wheel based cars, like my 71 Javelin and longer, don't get much benefit of the independent action. It is mostly a coolness factor. Outside of having a link setup for suspension stability. Which can be simply done to a straight axle.

I am sure your second time around, will correct the matter, for both comfort and long term use.

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390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2016 at 6:24am
The car rides and handles great with the IRS -- just some vibration and mechanical noise (along with road noise) comes in. I had talked to others with the IRS in "fat" 40s and early 50s cars mounted solid like I did, but those were all sedans. The wagon is worse as far as mech/road noise -- it reverberates up through the floor directly into the passenger compartment, no sealed off trunk/seat for noise insulation.

I've just about figured out how to mount the Jag cradle (or rear suspension crossmember, if you prefer). Here's a few pics of it raised in place under the car.








Edited by farna - Jan/27/2024 at 9:55am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2016 at 6:39am
It looks sweet, and don't know why you did not attempt using it in the begining... assuming it prolly looked simple enough to weld tabs or brackets to mount with.

Dont mind me, on proper naming convention, I have my odd way of sorts. Though most peeps understand for the most part.

My only thought before you mock mounted the Jag cage... was the ride hieght change. Though I would think your old mounting may be about the same maybe a wee lower in the back.

PS, your right about what you shared a while back on how things match up between the two makes. Like not much change to make it right.

To me the rambler wagon is still light and short ln the wheel base compared to later wagons. So IRS is quite the upgrade, and in your choice in setup, a good match.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2016 at 6:44am
As noted in the pics in the previous post, the front mounts are in near perfect position. They align with the Rambler rails great! Initially I looked at the TSM and noted that the widest measurement on the Rambler is within 1/16" of the outside measurement of the Jag mounts. Perfect! But the Rambler rails bow out in the center where they would go around the coil spring. Where the mounts need to go there is about a 3/4" gap on the outside and about a 1/2" gap on the inside. The Rambler rails are only 1-1/2" thick, the Jag mounts are made to go over 2-3/4" rails.

Front mount position - Rambler rail almost perfect!



Rear mount position - Jag rail is symmetric, same slope on both ends. Rambler has less angle in the back.



So it looks like I could make some spacers between the rails and mounts and bolt up. The rear one would still take one bolt, and I could just weld a piece of tubing across the bottom of the rear rail for the lower bolt. Perfect, right?

Not so fast!! As you will note with a quick look at a late 80s/early 90s XJ6 (my axle came from a 1988 model), the cars sit rather low. The reason the rear rail of a Jag unit body is at the same angle and lower than the Rambler is because the axle is tucked way up under the car. I need to put another inch between the Rambler rails and the Jag axle to get it back to where it was. I really think it needed to be at least 1/2" higher in the rear too.

I will either have to make spacers between the rails and mounts or weld spacers between the Jag mounts and cradle. Right now I'm favoring using rectangular tubing sized to fit the Jag mounts with vertical tabs to bolt to the Rambler rail rather than welded directly. Would make it easier to return to stock if anyone ever wanted to. The tubing would be placed so that it sandwiches between the Jag mount and Rambler rail, sitting evenly against the rail.

I am also mulling over raising the mounts though. If the bottom of the mount was even with the top of the cradle instead of lowered on the side it would be perfect. Will have to look and think some more on that.

In this photo you can see that moving the mount up would also move it in. Since I have a 3/4" or more gap on the outside that might move the outer "ears" of the mount even with the Rambler rail, only requiring a spacer on the inside. The mount has two bolt into the angled side of the cradle and one stud under the bottom. So I'd have to weld a tab or something under the mount for that bottom bolt.




So this is where I'm at now. It might be a few weeks before I get time to go over and take some measurements and do any work. So lots of time to think about it...



Edited by farna - Jun/24/2016 at 6:48am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2016 at 7:17am
I would not worry about welding a tab on the mounts.

Look at it as you started thinking of hieght gap and side gap.

Gosh I have some air craft aluminum segments that may be of proper thickness and length to mount against the frame.

Though my concern, not knowing the thickness of the Rambler frame, would the brackets crush the sidewalls of the frame when bolted through and under side load? You may have to weld in steel bolt tubes to prevent side load crush, like what AMC did on my 71 Javelin frame.

As for the distance for mounting the low side of the mount, you can either cut a retangular tube steel channel to weld inside the mount to extend and take up space between the rear frame, thus making less work at how much you need to change between frame and bracket mounting.

I try to simplify first then work on how things will mount after. So to me working with a short and wide bracket makes sense to use it as a saddle to cut and weld in place a proper extension to allow mounting to your existing frame.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2016 at 7:47am
I will make side plates for the rails that go from where they meet the body to the lower edge. That's what I did for the lower trailing arms on the axle. Strengthens them enough without the tubes. Can make them longer in the back so that lower bolt that would be just below the rail will go through the plates -- might use a tube on the outside there.

The more I think about it the more I like the idea of raising the mount on the Jag cradle rather than making a spacer between the Rambler rail and cradle. Either way works, and the spacer can bolt to the Rambler rail. Will mull over this a bit more before doing anything. Will likely be a while before I can get to it anyway.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Aug/01/2016 at 5:24pm
I managed to get about three hours to work on the car! Got new springs on two of the new coil over shocks for the Jag rear axle. Thought I had a differential side seal leaking, but looks like it might be calipers. Whew! One was a rebuild, the other (that leaks most) I rebuilt with a seal kit. Looks like I'll be ordering a pair of rebuilt calipers. Might see if Willwood has a pair that would work, or if a pair of aluminum GM calipers could be used... Those cast iron two piston Jag rear calipers (two opposed pistons) are HEAVY!!

Got the broken crossmember off the axle and figured out how I'm going to mount it. I needed to lower the whole Jag subframe/cradle about 1.5". So I put a 2x4 across the top and jacked it up in place under the car. Perfect position! Centered it all and jacked it up tight. The Rambler rear rail is 1.5" wide, gap between the Jag mounts is right at 3". So I have 1" on the outside of the Rambler rails and 1/2" on the insides to make up.

I'm going to see if I can get some 1" thick x 4" wide rectangular tubing, about 11 gauge. I'll need two ~5" lengths for the front outside and two ~7" lengths for the rear. Pretty sure I can't get 1/2" x 4" rectangular tubing, so will use 1/2" thick aluminum plate for the inside mounts. Will simply bottom the pieces out in the Jag mounts and drill for 3/8" bolts, then put in place and sandwich the Rambler rail between the inner and outer pieces and drill the rail for two 3/8" bolts.  Will probably use four bolts, two for each side, on the Jag mount end, just a pair of 3.5-4.0" bolts through the rails on each.

Well, just looked it up on-line... seems I can't get 1"x4", can only get up to 1"x3". So I'll get 1"x2" and weld together to make 4" width.  1/2" I can only get 1.5" 16 gauge (only 1/16" walls), so will go with flat aluminum stock there. Of course I could double 1/2" aluminum for the other side...  it's only $15 a foot... Could thread the aluminum and forego nuts... just use some loc-tite...

Anyone see a problem with using 1" thick aluminum (6061 flat bar -- doubled 1/2" flat) on one side and 1/2" on the other?  The bar lifts the axle about 1.5" above the "frame" rail then connects to the rubber mounts. With that thickness I don't think strength is an issue... anyone disagree?


Edited by farna - Aug/01/2016 at 5:39pm
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