mayberg

I feel like Rosanne Rosanna-Danna. It's always somethin'.

Today it was the rear leaf spring. I just don't have enough bite on the bolt holes on the front side of the rear end cover to mount the leaf spring. I'm thinking it's time to drill it out and insert a heli-coil. Any comments?

I can get grip in the bolts on the back side just fine. The front side is tough, and one is already boogered up to begin with.


[Modified by mayberg, 8:05 PM 4/21/2002]

Pedro'74

I'm far from a specialist, but can you trust a helicoil for a job like this? I think I'd only find peace of mind after replacing the diff cover...

-Pedro

Paul L

Pedro is bang on. Get a new cover. Don't fool about with this type of critical repair.

mayberg

What about the guys that use heli-coils for head bolts and such?

Pedro'74

Guy,

I may be completely wrong, but here're my thoughts: the heads are held in place by several bolts; if one fails, what could possibly happen? I have no idea, but in the worst case, the engine would go bye-bye, and your car wouldn't run. That's still far better than seeing your spring in the rear view mirror while driving on a highway at 70 mph.

-Pedro

MYPET70

:smash: :smash: I'm a huge heli-coil fan and am convinced that if you did it right, more than likely you'd never know the difference....HOWEVER, given the criticality of that union, the stresses/forces involved, and that there are only 4 bolts.... why take the chance? I would absolutely get a new cover. Good luck!! :smash: :smash: :D

74-Roadster

Since the longer bolts we used were able to bite, can you cut the front two of them down to where they are long enough to bite but won't penetrate inside too far? You can always paint the gold bolts black. :lol: :lol: :lol:

Otherwise, get a heavy duty cover from Muskegon.

KenSny

For the cost of a new cover, I'd feel a lot better than patching this area with a heli-coil. Not worth it IMHO.

Tom454

Heli-Coils will work fine if installed correctly.

They are available in different lengths from industrial suppliers such as McMaster-Carr.
A "standard length" insert which is all you will find at your local autoparts/hardware store may not provide adequate thread engagement.

When you buy a TRW (wide) style fiberglass spring, they provide you with thread inserts (and skinnier bolts) because the OEM bolts are too wide to allow the spring to be installed. Although I'm not a fan of this practice, it is an indication that inserts can be used successfully.

The flip side is, a Heli-coil kit with the correct length insert can cost you half to two thirds as much as a new cover... depending on where you buy the kit.

If you really, really do not want to remove the cover etc., then a heli-coil (if installed correctly) will work fine.

In your case, since the front two holes are blind, it would also be wise to order the special heli-coil tap as a "bottoming tap"... these are also available from McMaster Carr, and will provide maximum thread engagement as opposed to a standard "barrel tap".

Now... do you have a steel spring, or a fiberglass spring?
If steel, do not attempt to tighten the bolts with the spring in an "arched" condition.... the threads in the cover are not designed to "pull" the spring up. This is one way that they get stripped... as yours are.
Use the weight of the car to "de-arch" the spring before tightening the bolts.

Hope this helps.

Tom

mayberg

Tom,

I've got a steel spring. It's after-market, as the top leaves have a slight arch and I believe that originals are flat.

I agree with you regarding torqueing the bolts once the weight of the car is on the ground/spring. And when I plan on removing the spring, I loosen the spring bolts before I jack the car up.

But.....what about those times when the car needs to be jacked up for some reason and the spring is NOT to be removed. If the threads are not designed to "pull" the spring up, will they at least "hold" the spring while the suspension is unloaded?

Let me know your thoughts.

Tom454

Correctly installed, correct length Heli-Coils will hold fine.

Any thread, original or Heli-Coil, will strip when pulling the spring up because thread engagement starts out meager when the stress is the greatest. Bubba might get by doing this once, but probably not twice.

With good threads, once installed & torqued, they hold the spring just fine.

I am about to Heli-coil an 80 cover.... which is aluminum.

Tom

redvetracr

mayberg,
I am not sure which one it is (i had 8 rearends) but one of my covers had a helicoil, I never gave it a second thought. BUT if I was you I would take it to a machine shop and have them do it, it will save you from buying another tool you will (hopefully) never use again. ...redvetracr

Tom454

That's a good suggestion... just make sure you tell them you want full thread engagement...

If the hole is .7 inches deep, you don't want a .4 inch heli-coil in it.

It was that kind of shoddy machine shop work that got me started in the business 30 years ago.

Machine shops are not all equally competent.

Some will try to convince you to accept a krap job just because they are too lazy to order the correct part...
they want to use what they have in stock, or what they can get easily and cheaply at a local parts store.





[Modified by Tom454, 11:54 AM 4/23/2002]