Spring Shackle revisited

[DanOlson]

Anyone know or remember which end of the left front spring shackle is left hand thread? The frame end or the spring end. I've tried an impact on both ends in both directions but didn't whale on it too much. This may be the perfect justication to buy a Oxy Acetylene torch.

Dan

[DanOlson]

I've been working on the shackle off and on for the last couple of days with no luck. I've been trying LH and RH not knowing for sure what it is. If I was to cut off the shackle close to the spring and frame could the innards be driven out?

Dan

[Don Coatney]

On my Plymouth P-15 both are right hand threads. Are trucks different?

[DanOlson]

According to earlier posts, yes, the spring shackles on the drivers side are left hand like the wheel lug nuts. The replacement shackle I got from Rare Parts has one end LH and the other end RH.

[Young Ed]

Yup Don. If I remember correctly its the front of the front leaf springs he's having trouble with. there is one up there that is a lefty but I forget which one. I think its the spring end of the drivers side one. The shackle on a truck has a collar piece that is threaded on both the inside and outside. The outside threads into the spring and then the shackle threads into the inside of it. Hope that makes sense-kinda tricky to explain.

[Young Ed]

Here Don this one kind of shows it. The front spring is shackle mounted at the front and has a pin through it at the rear on the underside of the frame. The rear leafs are the opposite with the pin at the front. On these not only does the shackle wear out but because so many of these were worked so hard and not maintaned the big cast piece the upper rear shackle goes into gets worn out too. Very common to have to grind the rivets off the frame and replace those mounts. Roberts sells repro ones. Mine were only slightly worn so they were ground off and swapped side to side to the worn piece is on the bottom and not really weight bearing anymore.

[DanOlson]

My 53 is opposite that. Fixed in the front and shackle in the rear.

[Young Ed]

Thats interesting too. I wonder why that change? I know in 48 they moved the axle back. My 46 takes the same oil pan as a car but the pilot house engine I have has the sump at the front because of the axle move.

[Merle Coggins]

Yup, spring shackles moved to the rear of the springs, and the steering linkage changed to work side to side in stead of fore and aft as in the earlier models. This was to reduce bump steer.

My manual shows a cut-away of the shackle, but doesn't mention anything about left or right hand threads.

[Bob_Koch]

I know on the rear spring it's the bottom one - the one attaching the spring itself. i'm thinking the front is the same that's reverse threaded.

[DanOlson]

Good enough for me. I have a 50/50 chance, right?

Thanks, Dan

[TodFitch]

Yup, spring shackles moved to the rear of the springs, and the steering linkage changed to work side to side in stead of fore and aft as in the earlier models. This was to reduce bump steer.

My manual shows a cut-away of the shackle, but doesn't mention anything about left or right hand threads.

Everything old is new again. Your description and photo match how they did the spring shackles and drag link on my 1933 Plymouth. I wonder why they went away from it before coming back to it.

I don't recall any left hand threads on my "silent-U" spring shackles. I guess I should rummage through my spares to see what is there.

[Bob_Koch]

Here's a picture of the left rear that's opposite threaded. Don't know why the front would be different.

[DanOlson]

On my 1953 B-4-C, the shackle on the rear of the front left spring is left hand thread on the spring end and right hand thread on the frame end. This matches the replacement shackle from Rare Parts, RP35516. Anything I should know as I install the new one?

Dan

[TodFitch]

Anything I should know as I install the new one?

Dan

The only trick is to get the U in the correct position with respect to the frame before screwing in the bushing. Likewise get the spring in the correct position with respect to the U before screwing in that bushing.

The 1936-42 Plymouth service manual calls for "place a 7/8 inch gauge between the spring shackle and the frame side rail and between the end of the spring and spring shackle. Install the shackle bushing and remove the gauge." I imagine that the dimensions are probably pretty close on your truck to the older passenger cars. By the way the service manual continues: "CAUTION The lower leg of the left rear spring shackle has left hand threads. This is indicated by the notches in the lower shackle bushing (7, fig 6)."

[Bob_Koch]

Sure would have been helpful if they had put that in Our manuals

[DanOlson]

The inside of the spring eye and the frame is not actually threaded is it? Do you draw the shackle into the bushing?

Dan

[TodFitch]

The inside of the spring eye and the frame is not actually threaded is it? Do you draw the shackle into the bushing?

Dan

On the "silent-U" style shackles they are actually threaded. The idea was that all the contact area along the threads gave more lateral thrust control than a conventional plate sided shackle and that as the spring moved the shackle slightly screwed and unscrewed itself spreading the grease around.

As to actual threading, it did not look like my springs were threaded but the shackle bushing did screw in. Not sure if that was simply because of the threads on the outside of the bushing or not.

[Bob_Koch]

The U shackle is threaded. The springs are not as Tod stated. The shackle is the part that is reverse threaded so put that end on the bottom.

[DanOlson]

Thanks everybody, got the new one installed. What was throwing me was from the ridges on the outside of the bushing, at first glance there appeared to be threads on the inside of the spring eye and frame tube. After some cleaning it became apparant that there were just rust. The new one went in without a hitch. I didn't have a chance to test drive it last night but since it took a breaker bar and a 4 foot pipe to break the old one loose I think it's safe to say it was froze.

Dan

[TodFitch]

Thanks everybody, got the new one installed. What was throwing me was from the ridges on the outside of the bushing, at first glance there appeared to be threads on the inside of the spring eye and frame tube. After some cleaning it became apparant that there were just rust. The new one went in without a hitch. I didn't have a chance to test drive it last night but since it took a breaker bar and a 4 foot pipe to break the old one loose I think it's safe to say it was froze.

Dan

Those ridges on the outside of the bushing are what lead me to believe they are threaded on the outside as well as the inside. . .

Keep those Silent-U shackles lubricated and they will last a long time. Let them go dry and they will wear out pretty quick.

[MBF]

I think those grooves that are being looked at as threads on the outside of the bushings are meant as to increase the surface coverage of the lubricant (grease) throughout the shackle, bushing, and sping. TodFitch is correct. Kept properly lubed they will last a long time because the actual metal to contact area is reduce by the outer grooves, let these run dry and those grooves will wear down quickly and cause the shackle to develop side to side play. Just my 2 cents again! mike

[Jerry Roberts]

According to earlier posts, yes, the spring shackles on the drivers side are left hand like the wheel lug nuts. The replacement shackle I got from Rare Parts has one end LH and the other end RH.

If anyone else is going to buy these spring shackle bushings from Rare Parts , have them label the parts as to location . They can look in their book and get this information . It worked for me . They are in my hometown so even though their price was higher than others , the cost was the same as there was no shipping .

[chipsb3b]

Appreciate the discussion on rear spring rear shackles.

I'd like conformation please.

For a B3B (and probably all B Series) the left hand threaded shackle bushing should be located on the left (driver's side) spring at the trailing (rear) end of the spring - - - right?

[Fernando Mendes]

1/2 & 3/4 ton frame assembly