Changing from Threaded to Rubber Spring Shackle Bushings

[Sharps40]

If you're in the purest camp this post may elicit negative thoughts and feelings.   But, if you like to drive your car.....perhaps it will help.

 

This is a rear leaf spring conversion.

 

1937 Dodge D5 4 door sedan.

Old on top. New on bottom.

Old is 7 leaf. New is 8 leaf (850 lb rate).

The new made springs are for the 40s/50s Chrysler (heavier car) and others. All the measurements are the same. Sole difference is the rear spring eye is not threaded for the old steel Cee Shackles rather using the more modern Rubber bushings and shackles. The Cee Shackles were used on the 37 and many models before 1942ish in part due to a cross member just aft of the fuel tank.

I am lead to believe that a leaf spring rides best flat or with 1 to 2 inches of arch. Passenger side was flat, drivers side inverted. Time to replace. 86 years is a good run.

Doing a lot of research, it seems this particular spring length/rate was used Mid 30s clear up to late 60s on Mopars, and clear up to date on other items like trucks, trailers, other make cars, etc.

(Freshly installed, the new springs are giving me about 2+ a little inches of arch, so, even with normal settling, should be perfect for a long time.)
 

 

Edited November 22, 2023 by Sharps40 (see edit history)

[Sharps40]

Better view. 86 road years is a lot of flexing and the old springs have quite a set. Spring shops say that spring rate does not change with age but Arch will.

You might have them rearched (Factory arch should be 8.5 inches for MOPARS using this spring) but finding a shop that can...and given the low price of brand new springs...plus the upgrade to one additional leaf...and the ability to convert from those hard to service threaded bushings.....

[Sharps40]

The new part number. Available from lots of places, shop around for the best price. These were under $400 the pair shipped. NOS springs are still available with the threaded eye but its getting darn near impossible to find a matched pair.

 

[Sharps40]

The old shackles. These were righty tighty on both sides, others may or may not be so I try the socket in both directions and don't round off the head, they can be in the frame sleeve pretty darn tight.

I thought these would be the last of Ma Chryslers righty loosie stuff, but, thankfully it was all normal thread. Heaven knows if she stashed anymore backwards threaded parts in there but I think I got them all swapped out now.

 

Edited November 22, 2023 by Sharps40 (see edit history)

[Sharps40]

The new shackles and bushings, Boomerang style/heavy duty courtesy of the OffRoad types.

The old Cee Shackles measure 4 inches CTC. The new Boomerang Shackles (allow clearance of the aft cross member) are sold at 4 inches CTC but actually measure 4.5 inches CTC. Not a problem, thats only 1/4 inch lift out back. New grade 8 hardware, including grade 8 locking nuts were acquired. Some triming and reshaping of the inner shackle arm was required to ensure cross member clearance through out full stroke. Finally, a few washers are acquired to ensure the spring is aligned to prevent bind and breakage. (I used 3/8 thick shackles for strength since I knew I'd be trimming a bit.  (Shown below rough shaped prior to final smoothing, 1 each inner, 1 each outer, same shapes for both sides of the car.)  Not shown, a 2.25 in steel sleeve was used on the center bolt establishing a 2.9 in width across the shackles arms with the bushings compressed)

The bushings shown are rubber, 7/8" outer, 1/2" inner and of a length needed for 1 3/4" wide springs. (EG just a bit longer so they smush up and lock tight in the eye/sleeve and around the bolts.) I did not smooth out the old threads in the frame sleeve as rubber bushings do NOT rotate in the hole....they twist a bit with the shackles turning on the bolt. And those threads are really more round bottom and shallow, shouldn't be any problem at all.

Short leg goes up (Frame bushing) and large Vee faces the rear bumper to maximize clearance and stroke.

Edited November 22, 2023 by Sharps40 (see edit history)

[Sharps40]

New and old ride height. (Factory ride height restored!) Remember to leave all the bolts (including the axle u-bolts) slightly loose until you have weight on wheels. Jounce the rear end several times then torque the front eye bolts, snug up the rear shackle bolts to compress the bushings. Finally, tighten down the axle U-bolts.....then go ride.

[alsfarms]

Could you show a picture or two of your new install so we can understand your modification better. I am certainly considering this very modification on a 1937 DeSoto coupe.  Have you made any driver type upgrades to the front suspension?

Al

[Sharps40]

here is the old and new ride heights.   

 

Front is an off topic modern independent suspension, it had to be lifted with 1.5" raised spindles and 13.5" free height coils.   This put the front 1 inch below factory ride height.

 

Rear is an off topic modern differential but rides on the original semi elliptic springs.  The only change out back was the newer MOPAR compatible springs and replacing the worn out threaded cee shackles with the more modern bushing style shackles.

 

I'll go get pics of the rear spring install next.

 

[Sharps40]

Springs were purchased on Ebay, (McVeighs Truck Springs), 37 to 54 plymouth.  Also lists out for the later heavier chryslers.   Check your lengths with Tom and the old parts manuals, if lengths are the same, this 8 pack is likely to fit.   850 lbs is not a bad rate for these heavy old cars, for me it sits right and rides very nicely.   Nor more wallowing around and hitting the bump stops, and not too high.

 

Front spring eye is already bushed in rubber and steel so only the new grade 8 5/8 bolt and grade 8 lock washer/fender washers and nut was needed.

 

 

Edited November 25, 2023 by Sharps40 (see edit history)

[Sharps40]

drivers side rear outer.  Upper, mid and lower bolts, locking nuts are grade 8.   Washers used are grade 2.   Shackles are a heavy duty 3/16 thick.  

 

Edited November 25, 2023 by Sharps40 (see edit history)

[Sharps40]

Drivers side rear inner.   Used to look like the outer but needed a bit of trimming and shaping to fit up into the area where the rear gas tank cross member sits.   It also needed a bit of trimming to clear that same cross member as the lower spring eye deflects to the rear upon compression of the spring.

 

 

 

Edited November 25, 2023 by Sharps40 (see edit history)

[Sharps40]

Back to the drivers side upper outer.   Top bolt, through frame bushing.   I installed 1 fender washer to both compress the bushing head on that side and to stand the shackle slightly off the frame member.   Also, in this photo you can see the black steel sleeve that establishes basic width between the shackles there in the center.

 

Edited November 26, 2023 by Sharps40 (see edit history)

[Sharps40]

Looking again at the drivers side outer down at the rear spring eye, 2 fender washers were inserted between shackle and bushing to properly position the spring eye left to right for bind free motion.   As you can see, the bushings are smushed but not crushed.   No torque spec applied, just what felt firm with a 6 inch socket wrench.   I'll check and tighten as needed but most shackle nut specs do not exceed 35 ft lbs.   Its hard to "torque to spec" a squishy part.

 

 

Edited November 25, 2023 by Sharps40 (see edit history)

[alsfarms]

Your description of "wallowing" while driving and taking bumps is exactly a good way to describe the ride feel. I am anxious to update this same area on my old and tired 1937 DeSoto coupe. 

Al

[Sharps40]

Yep.   If your still running stock springs out front, might just change all 4.   But I don't know about doing the fronts with a shackle conversion as these years ran those odd ball shackles with the loop and extra bushings out front.   That might wind up being either nos or re-arch what you have if the front porpoises around or sits too low. 

[alsfarms]

I am going to replace the original Desoto 6 with a later but interchangeable Chrysler 265 6 to give the coupe a bit more stamina yes looking the original part. I have been thinking about a transmission change and adapt a T-5 to give an overdrive gear.

Al

[Sharps40]

I had a T5 in a 65 chevy truck with a factory spec 250 6 cyl.   It was ok.   After a while, I really got tired of rowing the boat.   That plus they do pop the fifth gear off the shaft.   Since its installed aft of the case on the outside of the main box and only held by a circlip all the pressure on it is to the rear against that thin retaining clip.  You'll know when overdrive is gone, loud bang and coasting when the clip jumps out of the worn groove and the gear slides back out of engagement.   Should still have 1-4 to get you home and the old school fix is to put in a new clip and tack weld the clip into the groove in the shaft.  All that said, I wouldn't do it again, rather opt for an overhead valve inline 6 or v8 and auto.   Not traditional but more power and torque than many hopped up flats and off the shelf parts when your're traveling.  Love the fellows with the old flaties but........ 

Edited November 25, 2023 by Sharps40 (see edit history)

[alsfarms]

I toured earlier this year with some flat head 6 Chrysler guys. I was impressed enough with the 6 performance and handling to stay with that technology. I know where I could get a 3 spd with over drive but I understand that long term reliability might be an issue. I have put many miles on a T-5. If behind a V8, not so sure that they are up to the task. Did you stay with the stock shocks on your Dodge?

Al

Edited November 25, 2023 by alsfarms
Clarity (see edit history)

[Sharps40]

Yes.  Stock Monroe out back on the factory mounts. .   Camaro sway bar fit in between the too.   You should have a front sway bar already 

 

Edited November 25, 2023 by Sharps40 (see edit history)

[alsfarms]

A sway bar really helps reduce the "wallowing".

Al

[alsfarms]

I am not sure, does your Dodge have the independent front suspension or a solid front axle?

Al

[Sharps40]

It originally had the solid axle.   I assume Desoto had solid axle with sway bar too originally.   

[alsfarms]

Actually, DeSoto had a decent independent front suspension along with Chrysler.  They rode nice but were a bit sloshy if not kept in good condition.  I was not sure about Dodge but was sure that Plymouth was a solid axle design.

Al

[maok]

Thanks for posting this 'conversion'. I wasn't aware the leaf springs were all very similar with all these models and not aware of the availability of this kit.

 

I had to do the shackle conversion because the threads in the chassis of my C7 Airstream were worn out.