89IROCZZ4

i may be buying a car with a 10 bolt that is busted. The car comes with a 10 bolt rebuild kit and 3.73 gears. What pieces could/should I buy additionally to beef it up? I don't want to pay $2k+ for a 12 bolt or 9" and don't think I'll be beating on it all that much, and not really ever with slicks, I'd imagine.

sofakingdom

iTrader: (1)

Just exactly how "busted" is it?

At least as important, what kind of rear is it?

I would not recommend spending one cent on any rear for these cars that isn't a 89-up with PBR discs.

As far as strengthening one, about all you can do is:

• Weld the axle tubes all the way around, in a fixture holding them straight
• An Eaton posi (NOT a Gov-Lock, NOT an Auburn)
• A pinion bearing crush sleeve eliminator
• Better axles; I'd suggest Superior brand, as they have rolled splines and are heat-treated AFTER splining, instead of heat treating BEFORE splining the way "custom" axles must be made
• A girdle type of cover
• Cap studs
• New yoke

When you add all that up, it's obvious why you don't want to do this to anything less than THE TOP OF THE LINE core. It'd be about like rebuilding a 305 short block, where you sink about 20 times as much into producing the product as the core costs, making the cost of the core to be a COMPLETELY INSIGNIFICANT factor in the total cost of the project. No sense in polishing a turd. Start out with the best core you can find so that when you are done, you have the best finished product possible.

89IROCZZ4

Thanks! It is from a 1989 IROC. What kind of price are we looking at for all of these things?

AlkyIROC

You need to know exactly what diff is under the car first. A 1989 IROC could have a 10 bolt but may have a 9 bolt. If it's a 9 bolt, upgrade components are few and hard to find.

If it's a 10 bolt then it will have 26 spline axles unless it's already been upgraded. We'll assume it's still original.

New 28 spline aftermarket axles $500 for pair.
LPW rear cover with bearing cap supports $170
Eaton posi $520
Assuming the "broken diff" has broken teeth, new 3.73 gear set $200

Your's already up to $1400 without other minor upgrades like the solid crush sleeve, welded axle tubes, ring gear installation kit with bearings etc and after spending that much, you still have a tiny ring and pinion. You can throw a lot of money at the 10 bolt to make it better but the tiny ring and pinion will still be the weak link.

For roughly the same price or a little more, you can upgrade to a 9" with 31 spline axles that can use a junkyard center section.

sofakingdom

iTrader: (1)

Does it matter? It's kind of like, either you pay whatever it takes, or it scatters itself even more often.

If you have a 89 rear, it most likely has 26-spline axles. Since you'll be buying both a carrier and axles, make them both 28-spline instead.

Axles aren't that much; about $225 a pair. Look up Superior EV10-4 on Summit. Crush sleeve eliminator is about $30 from Ratech. T/A cover is about $150, with the cap supports.

Sonix

iTrader: (1)

Hmm, now lets pretend I "know a guy", who did this, but did NOT use a fixture when welding the axles (*cough*). This fellow now has a vibration above 50mph, and after swapping wheels/tires, and rebalancing the driveshaft, it hasn't cured it. Is there a way to verify the straightness of the assembly now? Perhaps, without access to a machine shop? ie, how straight is straight enough?

sofakingdom

iTrader: (1)

Easiest way to verify the straightness, is with a straight piece of rod, and 4 cones that fit tight to it (similar to the ones they use on wheel balancers).

Check for a bent wheel or axle. Amazingly common, and easy to do without really trying very hard. Look for a flange that isn't perpendicular to the shaft anymore. Just put the car up on stands under the axle tubes, crank it up, put it in gear, and look for a wheel that wobbles. When you find it, swap the wheels side to side; if the wobble switches sides, it's a bent wheel; if it stays where it was, it's a bent axle.

Sonix

iTrader: (1)

I did try swapping wheels, no change (borrowed a friends "known good" wheels/tires). I also tried putting a dial indicator on the axle wheel flange. Nothing measureable. I tried to replace the axles, but realized drum axles are different from disc axles... I didn't want to buy new axles until I KNEW I needed them.

Straight piece of rod and 4 cones? I'm trying to visualize how this would work? I have used a tire mounting machine, and a balancing machine, so I can picture that.

AlkyIROC

The rod and cones is to eliminate the axles, carrier etc. The rod is a heavy piece of solid bar stock, 5-6 feet long and 1 to 1-1/2" thick. Cold rolled is better. The 4 cones replace the inner and outer bearings and have a hole through them that the bar just slides through. Once all in place, you can see how far out the outer bearings are to the inner bearings and if the axle tubes need to be straightened to put them all in line again.

Any welding onto the axle tube, especially all the way around to weld the tube to the center can easily distort the tube and cause a misalignment.

sofakingdom

iTrader: (1)

Exactly: good description.

You take out all the guts; put 2 cones in the pumpkin, pointed ends into the tubes; put the other 2 cones in the outer ends; slide the rod through.

If the tubes aren't straight, then all 4 cones won't fit into all 4 holes at the same time.

Most stock rears, you can chuck up in a big vise and stick a piece of 2" galvanized water pipe into the tubes and reef on it a little, and break the spot welds. I've often wondered how ANY of em EVER stay together at all.

Wouldn't be too hard to make a jig as described; use threaded rod, put 2 nuts and washers inside the 2 innner 2 cones, and 2 nuts and washers outside the outer ones. Break the welds as described, then assemble the apparatus into the remains; tighten the nuts, thereby aligning the tubes to the rod; then weld. Can't warp if it's held in place while heating and cooling.

Sonix

iTrader: (1)

Hmm. Smart Sofa & Alky. I can picture that. I can likely get some 1" ready-rod or something, but not sure where i'd get "cones" ready made.

Well, now that i've welded it around, i'll have a hell of a time breaking the weld (pre-heated and used a ~95% nickel stick rod...)

Alky - Would you happen to know a machine shop that would be able to test for straightness - and more importantly fix, my existing rear end - here in Calgary?

AlkyIROC

redi-rod may be too flexible even if it's 1". You need something heavy and solid that will always stay straight.

Cones can be made up by anyone with a lathe and some chunks of aluminum.

If you do a google search for differential (diff) alignment jig, you'll see lots of examples.