What is the best way to go about changing the backing plates on a 77 Corvette?
I see that I need to pull the axles, but I am not sure how. I was thinking of taking the differential cover off and hoping there was a pin or something? Is there something that I can take off without taking the diff cover off? I bought 3 valvoline 80w90 and the GM posi additive so I do want to change that *****.





Any advice is appreciated.
Thanks!

 

Why do you want to change the backing plate?
What you need to know before you start is that in constructing the trailing arm they start with the backing plate an build everything else around it.

 

is it an automatic?. i removed all that stuff for weight savings...lol, I live on flatland though too(florida)

 

Virtually everything comes off (spindle included) before the backing plate comes off

 

Wait, What?
Diff cover? backing plates?
What exactly are you trying to do?
Mooser

 

This is for a 3 speed automatic that needs parking brakes, but I am having trouble determining the best way to change the backing plates. The backing plates are bad in a few areas. The last owner gutted the parking brakes and tied the levers up inside the drum with plastic zip ties. Everything from the center brake cable needed replaced.

The car does seem to be almost built around the backing plates, but I think I figured it out. It looks like there are 4 bolts and nuts that hold the hub/wheel bearing together along with the backing plate and axle which seem to be about 6 inches long. I could not get them loose when I tried turning the nuts on the backing plate side, but I will try the bolt heads by the axle side, which I just discovered.

I will flush the differential out after. I bought 3 quarts of valvoline 80w90 and GM posi additive. Is the fill plug on the passenger side about halfway down on the diff? Also do I drain that by just loosening the bolts for the cover and let it leak out or is there a gasket that needs replaced once I crack it open?

I was following these directions when I discovered step #2 or 3 has the bolts heads to release the backing plates from the axles and wheel bearing/hub: inside trunion carrier yoke had me looking hard for a minute and on the outer end I saw the bolts for hub removal to remove the backing plates, I think.

Axle Driveshaft
REMOVAL AND INSTALLATION
1979 and Earlier Models
1. Jack the rear of the car up and support
with jackstands.
2. Disconnect the inside trunnion from the
carrier yoke.
3. On the outer end, bend down the locktabs
and wire-brush the bolts.
4. Scratch a mark on the camber adjusting
cam and the bracket to permit realignment.
5. Loosen the camber adjustment nut and
turn the cam so that the eccentric end points
inward. Doing this will push the trailing arm
out and give more room for driveshaft re
moval.
6. Remove the driveshaft, outside end first.
7. To install, position the inside end of the
driveshaft in the carrier yoke and asemble Ubolts
or clamp and bolts. Torque the bolts to
14-18 ft. Ibs.
NOTE: When removing and installing both
axle driveshafts, be certain to position the
carrier side yokes so that the trunnion seats
are at 90° angles to each other.
8. Install the outside end of the driveshaft
into the spindle drive flange. Install the locks
and bolts. Torque the bolts to 70-90 ft. Ibs.
and bend the locktabs up.

 

I think you'll find that, among other things, the axle needs to be pressed off/on to replace the backing plate. That's a tall order even for those of us that have done it before. (note: the "driveshaft" removal instructions you have above are not referring to the same stub axle that is contained in the trailing arm.)

 

To the best of my knowledge (and I've had mine apart), the spindles need to be pressed out to change the backing plates. I've never seen a two piece replacement plate (as were available for some chev's in the early 80's)
If your backing plates are toast, you'll need to take the rear spindles apart and you might as well do the bearings while your in there.
Before you get in any farther you might want to look up what's involved in doing the rear spindles.

As for the diff, since the cover is a structural part of the rear suspension you can't really just loosen off the bolts and drain like a regular chevy.
If it's on the car, siphoning it out of the fill hole is the normal(?) method

Just as a tip, when re-filling the diff, stick a pin through the hose and bottle lid to lock it on, there was a fellow here a few weeks back who dropped the tube into the diff and couldn't fish it back out.

HIH
Mooser

 

Trailing arm rebuild detail ....ought to give you an idea of what you're getting yourself into (and why the previous owner tied them off)

FYI: if you have more money than time you can buy the assembly rebuilt - bolt on and be done.

 

You guys are awesome! I think if I can get the spindles off and then pressed out, then I can get to the backing plate nuts with a socket. The backing plate nuts are very rusty, almost to the point of being gone so I might want to look into some new spindles, but I would rather buy a press and cut the threads which would be 5 times cheaper than buying new spindles. I am thinking that I will just get them apart and take them to a shop with a press to have them install bearings and remove the backing plate nuts. Another option for the backing plate bolts is to cut the nuts off and beat the studs out, but that would only be if I could find new stud bolts for the backing plates.
Thanks again!

 

Wow! This backing plate replacement is turning out to be a major project. I am doing the trailing arm rebuild and the trailing arm mounting bolts are going to need sawzalled out along with the shims due to rust which is a major pain, but after that I think I will have smooth sailing in the bushing and bearing replacement.

In the end the whole rear end is being rebuilt which the car really needed and I am sure my brother will appreciate it.

Does anyone know how to correctly shim the trailing arm mounting bolt?

Also I was thinking about getting a 6 ton shop press for $65 to remove and install the new bearings if it made things easier or could I just use a 2 jaw pulley puller which seemed to work fine for the pushing the strut rods out instead of a spindle knocker?

 

So what im hearing here, is that if your TA do not need rebuilt, dont bother trying to get to the backing plate just to replace it? I would have thought the spindles would come out a little easier than that...guess I was wrong!

 

My backing plates are messed up from the previous owner gutting the parking brakes and ripping the spring pins through the backing plates as well as rust and the brake lever holes are cut out and torn.

The spindles seem to be pressed on the trailing arm and pressed on the wheel bearing hub.

My trailing arm mounting bolts, cotter pins and shims are rusted solid. Here's my shopping list. Plus a sawzall blade.

Timken rear wheel bearing kit $80
Spindle support studs 8 22
Spindle support stud nuts 8 2.5
energy suspension trailing arm bushing set 21
6 ton shop press 65
trailing arm front shim pin 2 3.5
trailing arm mount kit 2 66
trailing arm front shim kit 42.5

I found some good videos on youtube:
http://www.youtube.com/watch?v=nZcCn...feature=relmfu
http://www.youtube.com/watch?v=vrAi1...feature=relmfu
http://www.youtube.com/watch?v=c-omV...eature=related

 

Also I was thinking about getting a 6 ton shop press for $65 to remove and install the new bearings if it made things easier or could I just use a 2 jaw pulley puller which seemed to work fine for the pushing the strut rods out instead of a spindle knocker?[/QUOTE]

If your parts are rusted enough that you need a sawzall to remove the trailing arms, I'm pretty sure a 6 ton press won't do it. I couldn't get mine apart with my 20 ton press. I had to take it over to a buddy who has a 50 ton press to get it apart. And yes I had decided it was either going to come apart or break. It came apart.

Rebuilding the bearings on these cars is probably the most technically complicated procedure on the entire vehicle. My advice is remove the trailing arm and send it to an expert like Van Steel to have it rebuilt. Then bolt it back on. This is not a job for an average mechanic.

 

Thanks again for the advice. This is definitely not a job for the average mechanic with average tools. I am currently stuck trying to cut out the trailing arms with a sawzall and it is not very effective. I bought a 9 inch sawzall blade that is for cutting through half inch thick of steel and I basically wore the blade out with little progress. I bought 5 blades for $20 but at this rate I might need 10 of them at least. Any ideas how I could cut the trailing arm bolts with more efficientcy? Cutting blindly with the tip of a sawzall is a tough job.
I at least got the trailing arm nut off today after letting it soak for a week in pb blaster, but the bolt won't budge. I beat the end with spike and sledge hammer but just deformed the end of the bolt. I tried beating on the rusted shims which seem to be the main problem because they are rusted pretty good to the frame. Very slow progress unless you guys have a better idea?

 

Nope, that's about what it's like
If you can't pull the shims out you need to go through them as well as the bolt.
The shims are just mild steel, the bolt is grade 5 (I think, maybe 8) so they cut easily with a sawsall
Blades, I like lenox, but hard to find at the box stores sometimes, I used Milwaukee
Their TORCH blades are very good, and they make a new Double duty one that's got a stronger spine.

Here's a recent thread
http://forums.corvetteforum.com/c3-t...arm-bolts.html

HIH Mooser

 

If your parts are rusted enough that you need a sawzall to remove the trailing arms, I'm pretty sure a 6 ton press won't do it. I couldn't get mine apart with my 20 ton press. I had to take it over to a buddy who has a 50 ton press to get it apart. And yes I had decided it was either going to come apart or break. It came apart.

Rebuilding the bearings on these cars is probably the most technically complicated procedure on the entire vehicle. My advice is remove the trailing arm and send it to an expert like Van Steel to have it rebuilt. Then bolt it back on. This is not a job for an average mechanic.[/QUOTE]

The original bushings are flared in place which will need to be drilled out vs. pressed (then you can pull/press them). You'll never install original bushings (and properly flare them) using a 6 ton press so waste of money in my opinion.

As others have advised, you've picked the most difficult repair on the car to start with. You can save yourself purchasing many high dollar, single use tools, by simply purchasing a rebuilt unit and installing it.

 

The OP was referring to using the press to disassemble the bearings, but you're right. The bushings are another reason to send the trailing arms out for rebuilding.

And yes, the trailing arms can be a b**ch to remove. Most of us have been through it. Hang in there. It CAN be done! Good quality sawzall blades, and a lot of beer.

 

Good point, guess I got ahead of myself when he stated he was going to rebuild the trailing arms now (which would include the bushings). No need to confuse the issue further for him so thanks for the clarification.

 

Thanks for the confirmation push!

I finally made some good progess last night and got one trailing arm out. It took a long time to cut through the shims and the bolt, but shaving by shaving they came off. I bought another set of sawzall blades with more teeth per inch for cutting thick metal which didn't make much of a difference.

Next I need to drill the bushings out, get the spindle nut off and cut the spindle support studs. Then do the same thing to the same thing to the other trailing arm. Plus I want to blast and paint them.

I was thinking of taking them to a local corvette shop in the Pittsburgh area to get new bushings and bearings installed correctly, only if they are charging less than $200 labor, otherwise I may buy a 20 ton shop press from harbor freight and press them in and out myself.

I understand how the bearings are installed correctly with the end play and adjusting the shim to get it correct, but I need to read and learn how the bushings are installed correctly with the flares. Just to make sure that the shop I take them to does the job right or so I can do it myself.

Here's to another trailing arm day.

P.S.
Tough job for an average mechanic for sure, but feel I am a little above average. I mean I don't just do oil changes and brakes occasionally. I have replaced a few clutches and will get involved with any job on any car system. Prior to this backing plate problem, I buffed the paint job, cleaned the engine, did a full tune up, replaced the valve cover gasket, the power brake booster, master cylinder, caliper, front swaybar bushings. Internal engine and internal transmission are the only jobs that scare me at this point.
After this rear suspension, parking brake and differential job, I will fix the headlight vacuum problem, one brake light problem, loose door panel problem, caulk the back window, and install new carpeting. Then see what else.

This car seems a lot simpler compared to my foreign tuner, except the parking brake backing plate.