WHAM!!!!!.......thump, clunk, clack....

[formula_gramps]

Seems like I've gotten to the point where it's a new problem every three weeks or so with this car. Last week I had to replace the wiper motor control module. Not fun. I can't believe where they stuffed that motor into. So far I've been able to fix everything, but I'm really starting to get worn down....... I'm sure some of you have found yourselves in that position.

(I have a '94 formula, 6 speed by the way, street use only ....)

Anyway, last night I hit a "stealth" hole in an area of road construction, and immediately thereafter knew I had a rear suspension problem. On the way home the car made all sorts of thumping and banging noises from the right rear.

Got it up on the ramps today and was shocked at what I found!

Apparently, the spring perch on the passenger side busted nearly completely off! Most of it is gone. The coil spring is of course free at the bottom, and is cocked slightly to the side pointing inboard of the car. How it didn't come completely out and take out a bunch of other nearby components is a matter of **** luck I guess, if you can associate "luck" with this event at all.

I looked at the perch on the driver side, and although it is of course rusty, it looks otherwise o.k. These spring perches appear to be just welded onto the axle housing.....is that correct? Assuming this is true, this doesn't look like an easy fix. I can't imagine there is a replacement part for this, other than replacing the whole axle housing.

I know a complete aftermarket replacement rear-end will run me over a thousand, and be a project that I probably would not want to tackle on my own, and perhaps that would be overkill anyway. A used one from a salvage yard would be only about $400, but with the same sized project to face, (not to mention the task of trying to find one in good condition at this point......).

I've learned so much here from this board and the experts who regularly post here. Maybe one of you has a more cost effective suggestion than the ones I've mentioned above. I hope so. Although I am getting worn down on this car, I still in fact, love my old black bird, and would hate to have to take it out by the side of the road and "shoot" it.

Any suggestions would be most welcome. Thanks!

[Jeff_in_Atl]

I bought a used axle from a 2001 6 speed car for $200. It only took about 2 hours to swap it out and that was me procrastinating.

BTW this is the first time I have heard of this one.

[MunsonGTA]

if it's just welded onto the axle housing, you could probably just fix it. you might be able to hack one off of a junked car, then take it to a local welding shop, and have it welded on.

[Injuneer]

Is the axle tube damaged in any way where the spring perch broke off? Did the housing tear at all?

[formula_gramps]

Thanks folks for all your quick responses........

To Jeff:
That's pretty intriguing, that the project only took you a couple of hours. I suspect you're a hell of a lot better mechanic than me....LOL. But I guess the important thing is that it demonstrates to me that this is a project that an old shade-tree mechanic like me could try and tackle. I'm searching for a used rear end from salvage yards now to explore that option further. Don't think I'll be getting as good a deal as you found though! Wow, 200 bucks! This would have to be done on stands, which I'm kind of phobic about. Don't mind working under a car on ramps, but jack stands give me the creeps, especially when you're applying a lot of force in your work. I think it's time for me to finally stop being a cheapskate and get an air wrench too.

To: "Munson GTA"

Yes, that would seem so be the lowest cost solution. Scare up an axle assembly somewhere, carefully remove the bracket, then have the car carried to a local welding shop. A good possibilty. Although, if I end up having to buy an entire rear end just to get the perch, and the equipment is in better shape than what I currently have, I might be more inclined to try the swap. Also, since the perch is on the top of the axle housing, I'm inclined to think the welding couldn't be done with the axle housing in place. Stay tuned....

To Fred:

I'm going to check that out today. I guess yesterday my reaction was typical of what happens when you find something like that....you know: "holy *bleep*!! My eight year old was in the back seat when that thing let go. It scared me a little when I got to see what actually happened. Glad we weren't too far from home!
I'll get under there with an inspection mirror and light to check the top of the axle housing to see if there's any damage. Assuming the spring didn't create any more carnage, are you thinking along the same lines as Jeff? BTW, I checked out your website, and I see you have a 94 Formula. Still a sweet machine in my book! And though I am frustrated with all the stuff that has had to be done to mine lately......OF COURSE I'm going to fix my poor bird!

To all:

While I'm pursuing a salvaged rear-end, I've noticed there are some that have come off of V6 firebirds. Am I correct in my assumption that these are not compatable with my Formula's rear end? I didn't think the regular bird came with a LSD. (By the way, I don't have traction control on this one....)

Thanks again to all!

Ken

[formula_gramps]

Fred..a.k.a "Injuneer"

To answer your question, it looks like the spring caused no damage other than the e-cable, and the brake line mount for that wheel. The top of the axle housing looks fine. The spring actually got caught atop the housing itself.....that was lucky I guess. That thing could have gotten loose and created a hell of a lot more havoc.

Went to your website and read the step by step on swapping out the rearend. Thanks for posting that. I think this is the way I'm going to go. Love all the extra goodies you put on your '94. That suspension looks really sweet! Don't think I can cost justify doing something like that, but I'm trying to get a newer rearend that I can clean up, paint, replace seals etc. ( maybe even a good time to rebuild or replace the calipers), then slap that sucker on.

(This is what I get for driving this car in New England winters......Lol. Every winter it transforms from one of the must sure-footed beasts I've ever driven to a 285hp hockey puck).

No luck trying to find the id. number on the front of the axle housing. As you said on your website, it's amazing what a rusty piece of *bleep* this thing is. Indiana Jones couldn't excavate the number of this thing! I'm pretty sure the Formula's for that year at least received limited slip differentials with specs of 10 BOLT, 7.6", 28 SPLINE AXLES---- but I'm not 100% sure of that.

That's what concerns me. As you said on a previous post on this subject, match the wrong rear with the wrong tranny and first gear turns your car into a "stump puller". Never heard that expression.....nearly fell out of my chair laughing!

[toddwirges]

All M6 V8 cars have the same 3.42 gearset, so as long as you get an axle from a M6 V8 car your gear ratio will be allright. This is important, because 3.42's are the highest gears that came from the factory. If you can't verify the axle is from a V8 car you could end up with an open diff, 3.23's, or 2.73's, all of which would not be a good thing in a M6 car. Fortunately, I think you'll have a pretty easy time finding a donor, especially if you are open to using an LS1 axle.

I will say, that you still need to be careful if you aren't 100% sure of the axle's history - because it is relatively common for people to change gears on these cars.

If your car does not have traction control (ASR) then your life is pretty simple if you get a full rear assembly, because you can use any M6 V8 axle from an LT1 or LS1 car. If you have ASR then you'd ideally want to get a ASR axle to have the sensor rings already in place.

The LS1 axles used larger rear brakes and a "drum in the rotor hat' parking brake system with better holding power than the LT1 style brakes. There was also a changeover to Torsen posi's in mid '98, which are generally preferred in mild cars because they aren't prone to clutch wear like the Auburns used pre '98. Most people would consider these to be worthwhile upgrades.

To some extent it goes without saying, but if you are going to do a full axle swap there is no better time to swap out the coil springs or replace the rear shocks. Rear shocks are fairly inexpensive and can have significant impact on the ride/launch quality of the car.

Finally, I would suggest saving a lot more than a couple hours if you are doing the job mostly by yourself without a lift or air tools.

[formula_gramps]

Thanks Todd....that's a lot of good advice.

So far, the only rearend I have come across is a 3.23 locking diff., which as you said would be a bad idea for this car.

Have to keep looking!

Yes, I will allocate a couple of DAYS rather than hours for this project. Experience has taught me that. I had also planned to put in new springs and shocks, replace any seals, and possibly rebuild or replace calipers if everything else goes well.

The rear that's in there now is limited slip. What's your take on a locking diff vs. L/S, assuming they even made a locking version for the M6?

Best regards,
Ken

[toddwirges]

A limited slip is all you want in a street car. A "working" Auburn or a Torsen are fine enough to keep both wheels laying down power.

By locker I think you are referring to a spool, or both rear wheels being locked relative to each other. Not a good idea on a street car. There is room for confusion here because people get the terminology mixed up.

Regardless, if it is a factory axle, not tinkered with, it has either an Auburn or Torsen, which is fine.

If the 3.23 is the only axle you can find... it'll work. Your speedometer would be just a tad off (you might be going 64 when the speedo says 60), and the car would be a little doggier off the line... but most people would have a hard time noticing the difference between 3.23's and 3.42's.

3.42 rears are rather plentiful, so I would just keep looking.

[Injuneer]

A "locker" is a spring activated unit that only has two positions.... open and locked. There is a sudden transition, not a gradual one like you get with a limited slip unit, generally accompanied by a loud clunk. Not great on the street, but not totally unfriendly like a spool. Big problem is part way through a corner, when the lock suddenly decides it wants to "lock".

Some cautions:

-93 M6's did not get the 3.42 gears. They were either 2.73 or 3.23 like the A4's.

-94 did not have the option for traction control. It was advertised in the sales literature, but was not available until 95 model year.

-he needs a 3-channel rear axle assembly, whether it comes from an LT1 or an LS1 car.

[bn_bullet]

Ken,

Where are you located? I have a few stock 7.5" rear-ends from either '95 or '96 Formulas that I would be willing to sell. All of them are from cars that had 12-bolt rears put into them. Two of them have 3.42 gears and one of them has a 3.23 gear. If you are anywhere close to Maryland, maybe we could work something out.

V/R
Brian

[formula_gramps]

Thanks again to everyone for their help.

I'm still looking for a correct replacement.......

Fred and "Bullet".....I sent each of you a private message.

Stay tuned!