anyone ever heard of this happening?

[TICK]

Good to hear that. So you were thinking that the transmission shifting too hard caused the rear end to crack?

The tail housing geartrain endplay of these transmissions is around 0.015" or so. I can't imagine having this movement would damage the rear end, since there's a slip yoke that allows the driveshaft to "stretch." Was the yoke maybe binding? Was it perhaps a coinsidence or I'm missing something?

I'd think maybe a drum, shaft, sprag or bearing inside the transmission is what would fail if shifting is too harsh.


In any case, glad the problem was resolved.

i'm fully confident, that the tranny was responsable for cracked carrier. that tranny shifted violently, i would brace myself when shift coming. it would startle passengers. they would ask, did you just hit something? id say yup, 2nd gear.

 

[The_Family_Tahoe]

I'm gonna jump out there and contradict this entire thread. I have a 610 lbs ft flywheel motor in an 8.5 axle square body with a Trac loc and 295s. It has held up fine for 1500 miles. I drive the snot out of it. Are you all rock crawling with 35 inch tires? How are you breaking the 8.5 axle? What's the weak link? Street driving with a heavy foot and I've no issues. Even with a couple of burnouts with the 295 mt radials. I would expect an axle break rock crawling, but street strip? Why does everyone hate the 8.5? Granted it's not the famed Ford 9 inch or a 12 bolt, but it's got its place vs the Ford 8.8 and the notorious 7.5. Who broke an 8.5 and how?

 

[stutaeng]

I'm gonna jump out there and contradict this entire thread. I have a 610 lbs ft flywheel motor in an 8.5 axle square body with a Trac loc and 295s. It has held up fine for 1500 miles. I drive the snot out of it. Are you all rock crawling with 35 inch tires? How are you breaking the 8.5 axle? What's the weak link? Street driving with a heavy foot and I've no issues. Even with a couple of burnouts with the 295 mt radials. I would expect an axle break rock crawling, but street strip? Why does everyone hate the 8.5? Granted it's not the famed Ford 9 inch or a 12 bolt, but it's got its place vs the Ford 8.8 and the notorious 7.5. Who broke an 8.5 and how?

I posted some torque ratings from performancetruck.net on the 10 bolt, 9.5" and 10.5" 14 bolts on a thread a while back. IIRC, the 10 bolt was rated at around 3600 lb-ft while the 9.5" was rated around 5,000 lb-ft. and 10.5 was around 6,500 lb-ft... numbers are numbers...I even did some basic math on engine TQ/axle ratio ratings on that thread...

I don't hate the 10 bolt, but have to accept it's one of the weak links in our 1500 trucks. Mine on my 1500 has made it to 260,000 miles under stock tires and a V6 with the G80/3.42s. I never really took the truck off road, but the few times I did, I was really careful I didn't go nuts on it (one time I was like 1,000 miles south of the US border, probably 20 kilometers from the nearest town, lol.)

For pavement only, it's fine. Throw some big tires AND a guy that likes to jab the gas, and you'll be rebuilding the thing in a matter of time...or the guys doing the crazy burnouts...or the guys with slicks at the track.

Admittedly, I think those are the guys blowing them up and NOT the guys just minding their business...then there's the G80/10 bolt "gov bomb" deal. I think the spider gears are prone to failure or the G80 in most those cases.

 

[stutaeng]

Here you go. Post #22:

Suburban rear axle into C1500?

"most 400's I find in the junkyard are beat to hell" then "10 bolt axles get a bad rap" Which one is it? The 9.5 is tough enough that often you can just find one and install it. Sure, check the brakes. Nobody is suggesting that every hobbyist knows how to build a rear end. Many can install...

www.gmt400.com

Good luck

 

[Schurkey]

The 8.5" axle--when equipped with DECENT BRAKES, is a fine axle for compact and intermediate cars. MOST (not all) 8.5" axles got too-small drums. A few got discs, or 11" drums.

For the record, the 8.5 axle I removed from my '88 K1500 because it was getting sloppy loose internally, is now under my friend's '89 K1500 because his 8.5 shattered, dropping gear oil and iron pieces in the road as the truck skidded to a stop.

God bless the 9.5" Semi-Float. It's what the K1500s should have had to begin with.

 

[TICK]

I'm gonna jump out there and contradict this entire thread. I have a 610 lbs ft flywheel motor in an 8.5 axle square body with a Trac loc and 295s. It has held up fine for 1500 miles. I drive the snot out of it. Are you all rock crawling with 35 inch tires? How are you breaking the 8.5 axle? What's the weak link? Street driving with a heavy foot and I've no issues. Even with a couple of burnouts with the 295 mt radials. I would expect an axle break rock crawling, but street strip? Why does everyone hate the 8.5? Granted it's not the famed Ford 9 inch or a 12 bolt, but it's got its place vs the Ford 8.8 and the notorious 7.5. Who broke an 8.5 and how?

you must have not read the original post. did not break a axle. the carrier developed cracks all through it, and floping around. i don't drive hard. most of my driveing is on roads. although some would say coming down my driveway is considered going off road. when you spend lots of money and time building this stuff, you don't take it out and abuse it. the cracks developed because who ever built that tranny was a classic jackleg.

 

[TICK]

when i took the 14 bolt outta the doner truck, and checked it out. when i turned the yoke by hand there was quite a bit of slop before the axles turned. thats part of the reason i installed the new locker and ring and pinion. im sure the broke 10 bolt had similar slop, as it was original to the 89. you ad a hard hitting tranny, or someone pounding the gas pedal. witch would be the equivalent. something gonna break when you violently take up that slop.