C2 trailing arm shims

[Joe L.]

Re: C2 trailing arm shims

I do a lot of C2 and C3 alignments. I'm probably the only shop in my region who will touch the rear alignment of these cars. For pre-1969 cars that originally used the longer 2 hole shims I always setup the alignment with the later slotted shims. If its a driver (won't be NCRS point judged) I leave those in and will even drill the holes in the frame for the 4" safety cotter pin. For owners that want original two holes I remove the slotted shims and install an identical thickness of shim pack inner/outer of the original type. Its really not that difficult to do. Easy removal of the trailing arm bolt is a balancing act, you have to have the vehicle weight on the arms and bottle jacks under the spring end and frame, plus a ratcheting strap around the arm and your lift ramp to get to a balance point where the bolt will slide out easily and allow you to insert the 2 hole shims and slide the bolt back in. You do not need to hammer in any shims, they should slip fit in tightly and when you tighten the castle nut on the bolt they will be firmly in. You should not be able to move the shims by hand after tightening if properly done. Same goes for the newer style slotted shims that are tucked into the frame pocket, they ought to be tight after torquing the nut/bolt. One other pointer, if using slotted shims install the long safety cotter pin before you torque the nut.

Edward------


Do you do these alignments on a "flat rate" basis or time and materials?

[Frank D.]

Re: C2 trailing arm shims

I do a lot of C2 and C3 alignments. I'm probably the only shop in my region who will touch the rear alignment of these cars. For pre-1969 cars that originally used the longer 2 hole shims I always setup the alignment with the later slotted shims. If its a driver (won't be NCRS point judged) I leave those in and will even drill the holes in the frame for the 4" safety cotter pin. For owners that want original two holes I remove the slotted shims and install an identical thickness of shim pack inner/outer of the original type. Its really not that difficult to do. Easy removal of the trailing arm bolt is a balancing act, you have to have the vehicle weight on the arms and bottle jacks under the spring end and frame, plus a ratcheting strap around the arm and your lift ramp to get to a balance point where the bolt will slide out easily and allow you to insert the 2 hole shims and slide the bolt back in. You do not need to hammer in any shims, they should slip fit in tightly and when you tighten the castle nut on the bolt they will be firmly in. You should not be able to move the shims by hand after tightening if properly done. Same goes for the newer style slotted shims that are tucked into the frame pocket, they ought to be tight after torquing the nut/bolt. One other pointer, if using slotted shims install the long safety cotter pin before you torque the nut.

I used the slotted shims and the safety cotter pin when my trailing arms were rebuilt -- on the '63. You can always pull the pin out for judging and swedge some dum-dum in the pinholes for judging for less of a point hit I guess.

Anybody that's driven a car with the trailing arm bushings completely gone knows how violent the motion is on accel/decel (you can steer with the accelerator) so why even take the chance on spraying shims along the road on a non-trailer queen ?

And yes, the final T/A bushing bolt torquing should be done with "weight on wheels" and re-checked in 200 miles or so.

[Edward D.]

Re: C2 trailing arm shims

Joe,
All work done here at Edz Vintage Vette Repair LLC is on a time and materials basis. Alignments vary from easy on freshly restored cars to difficult on rusty suspension vehicles. By the time an owner thinks they need an alignment there typically are other issues causing the drivability problems to correct. In front arm bushings, ball joints, wheel bearings, and tie rod ends need to be checked. In the rear the strut rod bushings commonly need to be replaced. If I have to remove a trailing arm to replace the pivot bushing we are out of the realm of typical alignment. In sum, the variability inherent in working on 50 year old cars pretty much prevents fixed rate anything.

[Frank D.]

Re: C2 trailing arm shims

Joe,
All work done here at Edz Vintage Vette Repair LLC is on a time and materials basis. Alignments vary from easy on freshly restored cars to difficult on rusty suspension vehicles. By the time an owner thinks they need an alignment there typically are other issues causing the drivability problems to correct. In front arm bushings, ball joints, wheel bearings, and tie rod ends need to be checked. In the rear the strut rod bushings commonly need to be replaced. If I have to remove a trailing arm to replace the pivot bushing we are out of the realm of typical alignment. In sum, the variability inherent in working on 50 year old cars pretty much prevents fixed rate anything.

So true.... My rear suspension rebuild included everything but the sombrero bushings - mine weren't that bad and the repros looked flimsy...the metal was 1/2 the size of the originals... I also went for a rebuilt steering box and an NOS coupler (these are becoming harder to find).
The 63 rides and handles like new now. For gosh sakes don't use poly...

On early cars owners might consider the reinforced differential mount bracket - especially if the mounting bolt holes are wallowed out..
Original vs reinforced - IIRC there is a TSB on the issue...

[Joe L.]

Re: C2 trailing arm shims

Joe,
All work done here at Edz Vintage Vette Repair LLC is on a time and materials basis. Alignments vary from easy on freshly restored cars to difficult on rusty suspension vehicles. By the time an owner thinks they need an alignment there typically are other issues causing the drivability problems to correct. In front arm bushings, ball joints, wheel bearings, and tie rod ends need to be checked. In the rear the strut rod bushings commonly need to be replaced. If I have to remove a trailing arm to replace the pivot bushing we are out of the realm of typical alignment. In sum, the variability inherent in working on 50 year old cars pretty much prevents fixed rate anything.

Edward-----

I'm not surprised, at all. I would have been absolutely amazed if you said you did it on a flat rate basis. I think anyone looking for a shop that would do a 63-82 Corvette rear alignment on a flat rate basis would be looking for a LONG time. They'd probably be looking for a long time for a shop that would do it, at all. In fact, if one came upon a shop that would do it on a flat rate basis, I would seriously question the competency of the shop and, certainly, their experience in doing the alignment.

[Joe L.]

Re: C2 trailing arm shims

So true.... My rear suspension rebuild included everything but the sombrero bushings - mine weren't that bad and the repros looked flimsy...the metal was 1/2 the size of the originals... I also went for a rebuilt steering box and an NOS coupler (these are becoming harder to find).
The 63 rides and handles like new now. For gosh sakes don't use poly...

On early cars owners might consider the reinforced differential mount bracket - especially if the mounting bolt holes are wallowed out..
Original vs reinforced - IIRC there is a TSB on the issue...

Frank-------


The reinforced bracket is the ONLY way to go for any 1968-79 Corvette. Period. It's also the way to go for 1963-67 with a caveat: GM never replaced the earlier non-reinforced brackets with the reinforced style for SERVICE of 1963-67 Corvettes even though they are functionally superior. I believe the reason is that the 63-67 underbody tunnel configuration makes removal and installation of the bolts difficult when the reinforced bracket is used on these model years.

[Frank D.]

Re: C2 trailing arm shims

Frank-------


The reinforced bracket is the ONLY way to go for any 1968-79 Corvette. Period. It's also the way to go for 1963-67 with a caveat: GM never replaced the earlier non-reinforced brackets with the reinforced style for SERVICE of 1963-67 Corvettes even though they are functionally superior. I believe the reason is that the 63-67 underbody tunnel configuration makes removal and installation of the bolts difficult when the reinforced bracket is used on these model years.

I can't say on the early midyears about the replacement practice by GM but here is the document I have on it... I have a reinforced bracket "on the shelf" for the 63 if I ever have the problem with the bolt holes but -- so far, so good...

[Timothy B.]

Re: C2 trailing arm shims

The reinforced bracket with the welded thick flat washers seems like it does not take up any more room in that area, that's the one I would use on a midyear car if needed.

The original parts included a lock washer and thick flat washer. To me it seems the problem arises when the top rubber cushion degrades and allows the up/down movement of the front differential mount causing stress in the bolt connection and the sawing effect loosens the bolts. This allows the grade eight bolts to hammer against the thin steel of the bracket.

Sorry if I got off topic, this post is about trailing arm shims.

[Joe L.]

Re: C2 trailing arm shims

The reinforced bracket with the welded thick flat washers seems like it does not take up any more room in that area, that's the one I would use on a midyear car if needed.

The original parts included a lock washer and thick flat washer. To me it seems the problem arises when the top rubber cushion degrades and allows the up/down movement of the front differential mount causing stress in the bolt connection and the sawing effect loosens the bolts. This allows the grade eight bolts to hammer against the thin steel of the bracket.

Sorry if I got off topic, this post is about trailing arm shims.

Timothy------


There were actually 4 different brackets over the 1963-79 period. The first was GM #3820186 which was used for 1963 only. The second was GM #3843683 which was used for 1964-E65. Neither of these brackets had any sort of welded reinforcements for the bolt holes. In late 1965 bracket GM #3868799 was used and replaced the former brackets for 1963-E65 SERVICE. This bracket had the welded washer reinforcements at one pair of holes. This bracket was used for L1965-67 and also for 1968 with manual transmission.

For 1968 another bracket was released and first utilized for all 1968 Corvettes with THM-400 transmissions and, thereafter, all Corvettes through 1979. This bracket, GM #3921657, had thick plates welded to both sides of the bracket. All holes were drilled through the reinforcements. This is the bracket that I highly recommend for any 1963-79 Corvette. However, as I previously mentioned, it can be difficult to install on 63-67 Corvettes since the cross bolts are difficult to install due to the driveshaft tunnel.

Is the 1968-79 bracket really necessary? Consider this: if the washer-reinforced bracket, GM #3868799, solved the hole elongation problem, the plate-reinforced bracket, GM #3921657, would never have happened.

[John F.]

Re: C2 trailing arm shims

I used the slotted shims and the safety cotter pin when my trailing arms were rebuilt -- on the '63. You can always pull the pin out for judging and swedge some dum-dum in the pinholes for judging for less of a point hit I guess.

Anybody that's driven a car with the trailing arm bushings completely gone knows how violent the motion is on accel/decel (you can steer with the accelerator) so why even take the chance on spraying shims along the road on a non-trailer queen ?

And yes, the final T/A bushing bolt torquing should be done with "weight on wheels" and re-checked in 200 miles or so.

Frankie, Can you post some close up pics of the long cotter pin installed for the shims. I have read the whole thread, but my pea sized brain has not seen it yet.