70 rear spring retainer plate(s) appear strange

[Bill L.]

I am crawling around under the rear suspension checking for play, dry rotted bushings, and other stuff before I decide whether to restore or not.

It is becoming obvious that a previous owner did some rear suspension work since all the half shaft u-joints are the Federal Mogul 231 u joints, strut rods are later style, and rivets have been drilled out of the rotors.

I found something on the rear spring retainer that does not look right.

There appears to be an extra plate on top of the spring mounting plate where the 4 bolts go through to attach the spring to the rear cover of the differential. It is a very thick plate that also has a bolt going through it that is parallel to the spring. I searched for pics and I have not seen this plate on any other C3 rear suspension.

What is it? Why would it be there? Hmmm.

My camera is broken Or I would attempt to post a pic.

Thanks, Bill

[Joe L.]

Re: 70 rear spring retainer plate(s) appear strange

I am crawling around under the rear suspension checking for play, dry rotted bushings, and other stuff before I decide whether to restore or not.

It is becoming obvious that a previous owner did some rear suspension work since all the half shaft u-joints are the Federal Mogul 231 u joints, strut rods are later style, and rivets have been drilled out of the rotors.

I found something on the rear spring retainer that does not look right.

There appears to be an extra plate on top of the spring mounting plate where the 4 bolts go through to attach the spring to the rear cover of the differential. It is a very thick plate that also has a bolt going through it that is parallel to the spring. I searched for pics and I have not seen this plate on any other C3 rear suspension.

What is it? Why would it be there? Hmmm.

My camera is broken Or I would attempt to post a pic.

Thanks, Bill

Bill-----


Without seeing it I can't tell you what it might be. However, I can tell you that it definitely did not come that way from St. Louis.

[Don L.]

Re: 70 rear spring retainer plate(s) appear strange

Agree a pic would be helpful.

Is the spring a replacement? A guess: if the spring is a replacement and its overall thickness stack up is less than the original, perhaps the plate is serving as a shim, thereby preventing the 4 center mounting bolts from being too long, thereby extending into the diff case?

I'm not quite sure I am completely following your description, so I may be off due to mis-interpretation. Sounds like a good excuse to get approval for a new camera. Timing's right

[Bill L.]

Re: 70 rear spring retainer plate(s) appear strange

Geez am I stupid. I have an I phone.

Here is the picture. No idea what it is and why it is there. The stock plate is sandwiched between it and the differential cover.

Thanks,

Bill

[Rich W.]

Re: 70 rear spring retainer plate(s) appear strange

That's an interesting piece..not sure what it would do?? Maybe some kind of upgraded thing to keep the bolts from moving?? That's ok..its not hard to fix.

[Bill L.]

Re: 70 rear spring retainer plate(s) appear strange

I have looked at a lot of corvettes since acquiring my 70 and I have not seen a plate on any other car like that.

Like you say Rich, it appears to be an easy fix. It also explains why I the exhaust is just slightly out of place.


Bill

[Don L.]

Re: 70 rear spring retainer plate(s) appear strange

Wow! Dunno what it is or what it might do, however, do be sure that when/if you remove it, the bolts aren't too long for the front 2 (blind) holes. Long bolts can break in to and rupture the diff casting.

[Rich W.]

Re: 70 rear spring retainer plate(s) appear strange

I was looking at this some more..maybe they had the spring off and didn't know about putting the weight of the car on the spring ends before they tightened up the bolts to the different cover..it may keep the bolts from spreading when torquing the bolts down without doing so..wonder if they did use longer bolts..can't tell by the pic..would be a good thing to make sure they are not to long..good point there..

[John H.]

Re: 70 rear spring retainer plate(s) appear strange

It's the forward mount point for an aftermarket trailer hitch.

[Kenneth B.]

Re: 70 rear spring retainer plate(s) appear strange

It's the forward mount point for an aftermarket trailer hitch.

BINGO
You are right on. I have seen it on miyear Corvettes but not on C-3'S
KEN

[Michael G.]

Re: 70 rear spring retainer plate(s) appear strange

It's the forward mount point for an aftermarket trailer hitch.

Bill,

Should you remove the bracket heed the advice Don doled out, bolts currently being used maybe too long for re-use.

[Bill L.]

Re: 70 rear spring retainer plate(s) appear strange

You guys are amazing. Mystery solved

I will be removing it maybe today. At least it is something easily undone.

What is the correct length for the bolts?

Thanks,


Bill

[Michael G.]

Re: 70 rear spring retainer plate(s) appear strange

You guys are amazing. Mystery solved

I will be removing it maybe today. At least it is something easily undone.

What is the correct length for the bolts?

Thanks,


Bill

My originals measure 3.5".....overall length.

[Russ S.]

Re: 70 rear spring retainer plate(s) appear strange

You guys are amazing. Mystery solved

I will be removing it maybe today. At least it is something easily undone.

What is the correct length for the bolts?

Thanks,


Bill

Bill, Be sure you have weight on the wheels when you tighten the bolts so you don't crack the bolt bosses..

[Larry M.]

Re: 70 rear spring retainer plate(s) appear strange

My originals measure 3.5".....overall length.

Two of the bolts thread into blind holes in the differential carrier. You DO NOT want to bottom these bolts out when torqueing and crack the case. I first threaded a longer bolt into these holes so I could measure the exact length needed. Then I made up two bolts that were about 1/8 to 3/16 inch SHORTER (than the exact length) for these holes. Be sure to include the lock washers in this measurement. Also, do this AFTER you replace any of the plastic spring liners, since the newer ones are thinner than originals.

THEN snug up the spring attaching bolts with a small wrench or 3/8 drive ratchet and socket, let the car weight back on the tires, bounce the suspension a few times, and finally torque to spec.

One of the blind holes on my car had a few bad threads, so I chose to use a torque value below the official GM spec to preserve the remaining threads. I did not want to strip out this bolt.

The fours bolts for my 1967 car with standard 9-leaf suspension and new (thinner) Quanta spring liners are as follows:

2 bolts are 3-5/16 inch long..... and
2 shorter bolts at 3-1/8 inch long for the blind holes.


Larry