sorry, but i've got to disagree with that statement. i swapped out the stock assembly for a Richmond gear set & the Auburn posi, and still broke the gears, every year, for 6 years.

as for hammering on it, yeah i was hard on it. but when you go and build a truck with car diff's (refering to GM here) it's bound to have consequences.

 

Do you have really large diameter tires?

And was the diff properly set up with the correct pinion depth, ride pattern, and bashlash settings?

My old buddy had an '80 Malibu with a 383 stroker with camelhump heads that I ported on it with a tiny 7.5" rearend and 4:11's with an Auburn cone posi which we set up to spec, and it lasted 3 full seasons at the track (3yrs) plus this was his daily commuter vehicle he drove to work every day, and it ran 11.40's off nitrous and 10.50's on nitrous (and that was even WITH slicks). It eventually did blow that diff and so then he put a 9-inch rearend into it, but that 7.5 lasted quite a long time. I also had a 7.5 in my old '85 Mustang that I put 3:73 gears into using the stock track-lok carrier with a moderately built 302, and it lasted probably around 3 yrs also, until I was showing off to a friend and side-stepped the clutch into 2nd and popped the spiders out. And it had a 5sp and I always beat the livin hell out of that car. Cars with automatics generally tend to be a little easier on diffs for the most part.

But if you had big tires on it then I can see why it cracked. I had a buddy with a Ford Ranger all jacked up too high and HUGE tires on it and he was blowing his diffs all the time I remember. He also had 4:11s in it to balance the ratio out since his tires were so tall. One time he stripped the splines right off one of his axles. Lots of stress.

I agree that 7.5's have their limits but for a kid on a budget, I think he could milk the stock diff along for a while until he got over the cost he spent to put the V-8 in. Then maybe if it blows he can put a tougher rearend in, and just match the gears to the front. Changing the front is too much trouble unless you have a full fab shop or want to pay someone big bucks to fab brackets and get something bigger in there. It all just goes back to the 'ol sayin: "Speed costs money, how fast do you want to go?"

 

nope, ran the factory LT235/75/R15's on a bone stock truck.

as for proper set up...........after the factory installed gears blew, i put in GM gears, but they didn't survive. after that i only put in Richmond gears, but they still couldn't stand up. and ring & pinion set up is the only work on my vehicles that doesn't get done by me. i have a long time friend-who's an ex drag racer-do the set up. he's owned a trans & driveline shop for the last 20-odd years, and his work has never been in question, i know it's the operator (that'd be me).

and i know that these trucks have crap drivelines (diff's & trans), but since i like the trucks, there's nothing short of building a tank that's gonna stand the test of time.

 

Hmm, well I dunno what to tell you. I beat on my '96 Blazer pretty hard and
it now has 120k miles on the stock rearend and it seems to be working just fine, and so is the transfer case. And I do even have 1 size bigger BF Goodrichs on it.

 

looking back through this thread, i realized i left out a crucial piece of info;

" '92 T15 Jimmy SLT, 4dr, 4WD, 1 of only 2 factory 5spds. in Canada, and stupid fast (R.I.P.) "

the fact that it saw (on a routine basis) 7 grand shifts, and 4 grand launches in 4HI, was what i was refering to when i said...
it's kinda "apples & oranges", but i never had any diff issues with the '81 LB Chevy i built, and it was running a 337 horse SB, backed by a Super T10. and i didn't even change the original diff in that truck-it was a factory 250 cu.in. w/three-on-the-tree, running a 10 bolt.