Rear end blown - Pontiac GTO Forum
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post #1 of 20 (permalink) Old 06-10-2016, 10:12 AM Thread Starter
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Rear end blown

I don't know if I'll ever get a full summer out of this car anymore. Ziggy just turned 12 on June 7th but the week before on Memorial Day she took the opportunity during a drive out to Lake Michigan to blow the rear end out on the way back. I had the wife with me so she got to see how you do it. I had pulled out onto a main road with no one around and just nailed it (no clutch dump) in 2nd gear. The wheels just spun as we wiggled down the road and I hit third and continued the spin.

I backed off at about 70 mph and almost immediately smelled rear end fluid even though we were cruising that fast. That was followed by some awful noises from the rear. We made it a short distance down the road before it quit altogether. Tow trucks on a holiday are expensive.

I got it off of the flatbed and he was able to get it almost all the way into the garage and we pushed it in the rest of the way. The driver's stub was out about a 1/2" with grease all over the underside.

Getting those top 4 bolts that hold the diff to the subframe was a major pain. I think I may have used Lock-Tite when I put that pumpkin on years ago because they would not budge. I finally made a "breaker wrench" out of a pry bar hooked on my combo-wrench and the bolts begrudgingly came out 1/8th turn at a time.

After draining out shiny silver fluid I got the Harrop cover off and inspected the damage. I had sheared all the bolts off that hold the posi to the ring gear and there was gobs of ground metal inside.

Looks like I'm going to send it out for a major rebuild with new 3.73 gears and a Wavetrac posi. The last problem I have is I can't get the driver's stub out. I'll be "renting" a wheel bearing puller to see if I can slide hammer it out. Another summer with at least 6 weeks on jack stands and another $3,000 into the money pit. Take note kids that use it for a daily and don't have a bank account. This car is not for the weak of heart, having to pay someone to do your work or needing to be easy on your wallet.


2004 Blk/Rd M6
6.3 litre LS1

Built and tuned by svede
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post #2 of 20 (permalink) Old 06-10-2016, 11:13 AM
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Time to tub it out and go 4 link w a dana 60.

Seriously though, sorry to hear she broke again.
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post #3 of 20 (permalink) Old 06-10-2016, 01:39 PM
 
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That sucks!! It's been one thing after another for me the last 6 months as well. Every time I fix something another thing goes bad lol. Good thing i like to work on cars... This car is not for the faint of heart...

BUT I WILL ALWAYS LOVE MY GOAT!

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #4 of 20 (permalink) Old 06-10-2016, 08:32 PM
 
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Yes I have to agree you just never know what around the corner. But the nice thing is a lot of the work you can do. Rearend different story but keep spirts up and I guess save the penny for the rainy day fund. Doug
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post #5 of 20 (permalink) Old 06-10-2016, 10:39 PM
 
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Sheered the ring gear bolts off the M80 ring gear...d#mn. Sorry to read this! Been a while since ran across sheered ring gear bolts in conventional live axle diff build. Reads like after various diff upgrades, you have found a weak point.

For frame of reference, how many aprox ft lbs of torque was being sent to the ground with your well enhanced stroked LS1 6 spd combo? 575? What rear tires? even with new lift and overhead trans jack, doubt I will be taking on any R & R's on M80's, say that, though stranger things have happened.
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post #6 of 20 (permalink) Old 06-11-2016, 01:35 PM Thread Starter
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I'm probably only around 460-475 peak but that's in 4th gear. With the torque multiplication of a 6 speed in first and second gear 3.91 rear end gears and how much low end torque that comes on at low RPM it's a killer. I run 275 NT05s in the back on 9" wide wheels. New build will be with 3.73 gears, ARP hardware and a Wavetrac posi.

Two years ago was over 5 grand for the stoker build, Almost 4 grand last year with heads and cam and then this at over 3 grand it's been an expensive stretch. I'm probably close top 50 grand with the new purchase price, upgrades and repair and that's all parts. I do almost all the labor including tuning myself. Setting up a rear end is more than I want to tackle though so doing the R&R is enough for me.

I finally got the stub out the one side with a lot of effort that I really feel today. I "rented" a slide hammer and front wheel bearing plate to see if I could knock it out. The plate holes did not line up but after some thought I found the driveshaft adapter plate has 3 bolt holes that line up perfectly. There's a hole in the center that the pinion nub sits in that the slide hammer rod fit in. With a nut on the back side it took almost 20 minutes of slamming as hard as I could on it to get the stub out. After thinking I was wasting my time I found it moved about the thickness of a sheet of paper with each hard slam. Slowly, slowly it came out with resistance the entire way. When I got it out it looked completely undamaged. I have no idea what was locking it in so well.



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post #7 of 20 (permalink) Old 06-23-2016, 08:55 AM Thread Starter
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The pumpkin should be in the builder's hands in Cali today and I just received the Wavetrac. I'm now labeling it to send off right away. I'm missing not having my car with it always on jack stands but my buddy who has a '70 Chevelle SS that he did a complete frame-off restoration two years ago got into an accident last night and both sides got crushed. At least as long as my garage stands Ziggy is safe.


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post #8 of 20 (permalink) Old 06-24-2016, 07:59 AM Thread Starter
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The pumpkin arrived out to Mike after the long journey to California. Shipping 93# 2,200 miles ain't cheap. Mike got a look-see at it today. I knew one adjuster was shot and all of the posi bolts were sheared off. The other adjuster turned out to be jammed so that one needs replacing too and I need an adjuster locking tab. So far only the case and Harrop are re-usable.

Now I'm looking for a 05/06 pinion yoke. It seems the stroker is a torque monster and I need a beefier propeller.


So it begins




The inside was filled with a handful of metal shavings. I'd already scooped most of it out before I sent it



The one side adjuster has mushroomed into the housing and made nice little slivers of metal. I guess it took grinding and some work to get it out



The bolts were all sheared off, everything shifted and ground into the bearings and adjuster and the LSD was split into pieces











This is the propeller yoke thing I need but for a 05/06 so if you know of any one that has one. . .


2004 Blk/Rd M6
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post #9 of 20 (permalink) Old 06-30-2016, 03:28 PM
 
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Man that stinks. I'd have to say a second vote for Dana 60 time...
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post #10 of 20 (permalink) Old 07-06-2016, 09:57 AM
 
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Who do you recommend to rebuild this differential?
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