Rear Spring Bushings / Isolator / U Bolts

[Fresh Air Inspector]

Hello All,

If this thread should be in the 'Police Cars' section, please let me know.

I'm approaching the half way point in what will be a 3 year project restoring / modifying a 1988 AHB code Plymouth Caravelle (aka Gran Fury). I've just pulled the 8 1/4" rear axle out to replace the original 2.94 open diff with 3.55 Sure Grip. The original bushings, isolators and U bolts are toast. I suspect a number of you have been down this road already. So ....

1. U Bolts
What type of U bolt did you use? I have been unable to find ones that match the factory items; the underside of the curve has been flattened to better spread the axle tube load and the underside of the flattened portion also has an X pattern stamped into it to better grip the axle tube. The axle tubes are 3", the U bolts are 3/8" with a height of 4 3/4". Any recommendations?

2. Leaf Spring Bushings
The front bushing is the large oval one with the metal outer sleeve. The rear shackle is a 'stepped' design with the frame mounting about 4 3/4" wide and the leaf eye at about 3 1/2" wide. Based on what I have found online, this 'stepped design' appears to be unique to the AHB code (police package), vehicles. I have new standard after market items for the front and shackle bushings but would prefer Polyurethane to match all the bushings I have for the rear sway bar, front suspension and motor mounts.

3. Shackle Studs
The studs that support the bushings in the shackles have some corrosion, I would like to replace these. Since I believe these shackles are unique to the AHB code vehicles I will need to replace these studs. These are welded into one side of the bracket, I assume that these can be drilled out and replaced with a grade 8 bolt of similar dimensions? Anyone done this?

4. Isolators
These are well past their 'sell by date' and need to be replaced. It appears that ESPO Springs 'n Things carries these items as well as the front leaf spring bushings and shackle bushings. Has anyone used their products? Happy with the quality? Or is another supplier recommended; Firmfeel?

Looking forward to the feedback.

 

[Aspen500]

Espo, highly recommended. You need to order by phone, but worth it just to talk to the lady that answers.

How corroded are the shackle pins? Some pitting isn't a big deal.

 

[Fresh Air Inspector]

Hello Aspen500,

Appreciate the quick reply. ESPO - noted.

Shackle Pins - enough corrosion to reduce the diameter although I haven't measured as yet. Hope to get at that tomorrow (Fri). The query about replacing the pins was to have a Plan B in case I needed it.

 

[Aspen500]

Problem with using bolts is, the threads will chew up the bushings. Also there's no shoulder for the other side of the shackle to torque the nut to.

You could, however, make sleeves to go over the bolts for a bushing surface, and for each side of the shackle to tighten against.

Far as I'm aware, only the regular straight shackles are availible new from Mopar and also the aftermarket but not the HD ones like an AHB uses.

You can get u-bolts from ESPO or most any parts store. Unsure if any of them are flattened. Fully round works fine though, unless you're going for 100% original appearance that is.

 

[AMC Diplomat]

I second Espo Springs and Things. I couldn't be happier with the whole experience. Link: Leaf Spring Shackles, Bushings, Ubolts | ESPO Springs n Things

 

[Mikes5thAve]

I've usually gotten the various bushings and U-bolts from local spring or truck shop. Theyve always had it all in stock and better prices then l online. But they won't have the iso pads and probably not the oval bushings either so you could get everything from the same source online.
For the shackles if the pin in them is that bad you could probably get away with cutting snd drilling it out and then either get a rod the proper diameter and thread each end for nuts or see if you can get a bolt the right size that only has the end threaded. Sleeving it might work also but you'd probably need to drill the bushings a bit bigger to fit over it.

 

[Duke5A]

Are you willing to deviate from factory at all?

 

[Fresh Air Inspector]

Hello All,

Great feedback. ESPO is able to provide all the polyurethane bushings including those for the AHB shackles as well as the U bolts (7/16"). The U bolts are not exactly the same as the factory ones (flattened curve), apparently the originals are now 'unobtainium'. But are the correct dimensions.

Regarding the feedback about the shackles - a good sign of a healthy and active forum;

Duke5A - I'd rather not deviate from factory.

Aspen500 - Fortunately only the lower studs have corrosion. The plan is to use a long 9/16" grade 8 bolt, these will have a long shank. Of course the threaded portion will be too large in diameter as well as being too long. A machine shop can easily undercut the threaded end to match the thread length and diameter of the original. The bolt head can be machined to the factory 5/8" round head for welding as well as adding knurling to the top of the shank for a 'press fit' into the shackle flange. Needless to say these two bolts won't be cheap but at least the shackle will be back to the original factory design. Plan B is to use 7/16" grade 8 bolts with a sleeve - provided I can find a sleeve with the correct ID and OD.

Mikes5thAve - Appreciate the thought. I would love to support local unfortunately we don't have any other than NAPA and Bumper to Bumper. The only bits available locally were the U bolts, which were significantly more expensive than ESPO even are USD conversion, shipping, duty and taxes. Where I live is quite rural and the only major city in this province is Halifax, a 1 hour drive one way. Plus the chances of a supplier there having bits for a 1988 vehicle is slim to none. So, 99% of the bits for all my vehicles come from online sources in the US.

It will be a number of weeks before I get this sorted as the rear axle needs to be rebuilt (3.55 + SureGrip), before reassembly. I'll update this thread when I have all the bits to hand.

 

[Mikes5thAve]

I thought that might be the case being in NS. Luckily we have a couple truck shops near by, the first couple times I did axle work they didn't have U bolts that size so I actually got to see them make them which was pretty neat.
All the bushings other then the ones I noted are pretty standard it's too bad most of the old style psrts stores are gone because those were the guys who were more likely to find stuff like that. Rather then if it's not listed by car you're s.o.l.

 

[volare 1977]

Be easier to buy new shackles an cut the lower studs off and reweld to the old ones. or put a ad out there for some good used replacements. Pretty sure they used those same shackles used on the 93 minivan. 4094060 is the part number i believe

 

[AMC Diplomat]

Be easier to buy new shackles an cut the lower studs off and reweld to the old ones. or put a ad out there for some good used replacements. Pretty sure they used those same shackles used on the 93 minivan. 4094060 is the part number i believe

Right as usual, Link: Rear axle/suspension rebuild

 

[AMC Diplomat]

You might need to start investigating other shackle options and see what is close enough, as the chrysler stuff is hard to find
This is the rear shackle out of a Toyota Tacoma 4wd 95-04

I don't know what the measurements are, but surely there's another option out there that will be "good enough"

 

[Fresh Air Inspector]

Hello All,

AMC Diplomat - interesting Toyota shackles, unfortunately they are $77 CAD each ($57 USD), and may not be an exact fit. Hopefully this will work for another forum member.

Received my repaired rear shackles from the machine shop. He charged me $80 CAD ($60 USD) for the two shackles. This was in addition to the two grade 8 9/16" x 5" bolts at $2.60 CAD each ($1.95 USD). BTW, I could not find grade 5 (original factory type), in 9/16". Cost effective solution from my perspective.

The original studs are knurled at the base and pressed into the shackle. The machine shop rounded the bolt head so it could be welded and turned the threaded end to match the original bushing length and thread end (3/8" thread). Attached are the pictures.

I have all the ESPO Polyurethane bushings just waiting for the rear springs to be re-arched (minor adjustment), by a local truck shop and the rear axle rebuilt (3.55 gears + LSD + bearings / seals), by a close friend (has experience that I don't .

Hope it helps.

 

[AMC Diplomat]

Hello All,

AMC Diplomat - interesting Toyota shackles, unfortunately they are $77 CAD each ($57 USD), and may not be an exact fit. Hopefully this will work for another forum member.

Received my repaired rear shackles from the machine shop. He charged me $80 CAD ($60 USD) for the two shackles. This was in addition to the two grade 8 9/16" x 5" bolts at $2.60 CAD each ($1.95 USD). BTW, I could not find grade 5 (original factory type), in 9/16". Cost effective solution from my perspective.

The original studs are knurled at the base and pressed into the shackle. The machine shop rounded the bolt head so it could be welded and turned the threaded end to match the original bushing length and thread end (3/8" thread). Attached are the pictures.

I have all the ESPO Polyurethane bushings just waiting for the rear springs to be re-arched (minor adjustment), by a local truck shop and the rear axle rebuilt (3.55 gears + LSD + bearings / seals), by a close friend (has experience that I don't .

Hope it helps.

View attachment 51880

View attachment 51881

View attachment 51882

I'm curious, if you have the time, as to what the measurements are on your shackles. I did find measurements for the Toyota shackles. This might help the next guy suffering through this.

 

[Fresh Air Inspector]

Hello AMC Diplomat,

I don't have time to make a nice engineering drawing but did do a crude dimensional sketch (see attached picture). BTW is used a set of calipers as opposed to a tape measure so the values will be very close.

The Toyota drawing does not reference the stud diameters so that will need to be checked against the 9/16" that Chrysler used. The dimensions shown below are close, don't know how one would take up the extra clearance. The upper stud on the Chrysler shackle is 2.4mm (had to use metric), wider and the lower one 7mm wider. This does not include the 'dished' recess. Also, the smaller stud to stud distance would have the vehicle sitting slightly lower in the rear.

Dimension Comparison;
Toyota Mopar
1. 4.090" to 4.1875"

2. 2.598" to 2.875"

3. 3.35" to 3.6875"

Please note, the Chrysler shackles have a dish shaped recess at the end of each stud. I assume this is to allow the rubber portion of the bushings seat better. Having said that, the stock replacement bushings (AC Delco brand), have this shape. However, the ESPO Polyurethane ones are flat where they contact the shackle face. Don't know how this may, or may not, effect the performance of the bushing.

Hope it helps.

 

[AMC Diplomat]

Hello AMC Diplomat,

I don't have time to make a nice engineering drawing but did do a crude dimensional sketch (see attached picture). BTW is used a set of calipers as opposed to a tape measure so the values will be very close.

The Toyota drawing does not reference the stud diameters so that will need to be checked against the 9/16" that Chrysler used. The dimensions shown below are close, don't know how one would take up the extra clearance. The upper stud on the Chrysler shackle is 2.4mm (had to use metric), wider and the lower one 7mm wider. This does not include the 'dished' recess. Also, the smaller stud to stud distance would have the vehicle sitting slightly lower in the rear.

Dimension Comparison;
Toyota Mopar
1. 4.090" to 4.1875"

2. 2.598" to 2.875"

3. 3.35" to 3.6875"

Please note, the Chrysler shackles have a dish shaped recess at the end of each stud. I assume this is to allow the rubber portion of the bushings seat better. Having said that, the stock replacement bushings (AC Delco brand), have this shape. However, the ESPO Polyurethane ones are flat where they contact the shackle face. Don't know how this may, or may not, effect the performance of the bushing.

Hope it helps.

View attachment 51884

You're awesome, thanks for taking the time to do this

 

[MoparDan]

I remember when I had my leaf springs replaced sometime in 2014 that they had to have a nearby spring shop make new U-bolts, the only other thing I can remember was that some replacement bushings weren't available anywhere but others were, so some bushings on mine are new (ok ten years old now) and others are still from 1985... I've heard the are all available now

 

[AMC Diplomat]

Here's another set of shackles that I'm trying to find measurements on to see if they're "good enough" They're from 60s Chrysler station wagons
https://www.ebay.com/itm/402777490698?

 

[volare 1977]

NOS MOPAR 2525469 1965 P,D,C WAGON REAR SPRING SHACKLE/BUSHING PKG | eBay 2525469 look quite long in other pics I have seen.

 

[SRTMirada]

For those with fabrication skills this picture might provide some inspiration.