CHEVY 7.5" Small 10 Bolt

[bustingear]

Is anyone experienced with the 7.5" ten bolt rear? I have one under my a-bone. When hot it slips alittle on the break away. It almost feels like brake drag. I rebuilt the Powerglide recently and the 350 block. When I jack it up, there seems to be a little slop or hesitation between when the drive shaft turns and when the wheel starts to spin. I did this in neutral and by hand. Is there an adjustment to get those gear closer? Should I just replace the gears? I dont want to roll under a whole new rear as my four bar links and the panhard par mounts are already welded in. Any suggestions?

[yorgatron]

a very tiny amount of backlash will translate into what seems like a lot of movement at the yoke,seems to me you could remove the cover and have a look inside for strange wear patterns or broken teeth or whatnot.is the big nut that holds the pinion yoke on good and tight? sometimes the pinion bearing pre-load loosen up from too many hard launches-george

[hotrodsnguns]

Differentials do not slip they break. If you have slip check the tranny or clutch. If it is broken enought to appear to slip you will have one hell of a thump.

[bustingear]

I think you mean the external nut on the shaft that runs out the front to the drive shaft?

Also the set up is automatic no clutch. Like I said just had that Powerglide rebuilt. The same thing was happening before and after. Ony really does this when hot. No thump or thud.

What is the pinion bearing pre-load?? Is there and adjustment? Can the bearings be replaced?

Any more ideas?

[yorgatron]

is that a limited-slip or posi? have you ever looked inside? http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

[colorado51]

How is the torque converter? Did you replace it when you rebuilt the trans?

Doesnt really sound like a rear end problem, but you could at least pull the cover off and make sure everything is nice and tight. Those 7.5 10 bolts are not the strongest rears around, thats for sure.

[stoggie]

I have done a lot of late model Malibu/El Camino that use this rearend. The last time I re-did the car I went completely through the rearend. The 7.5" is famous for gernading under horsepower. I was always fortunate...knock on wood.
If it is a "posi" it could be the Auburn style diff that is a little finiky(sp?) when they start to burn up. I had one that I had a hard time getting parts - I could only buy them directly and it took a month. I suggest opening it up and looking inside for abnormal wear and such as noted in the first reply.

[bustingear]

The torque converter was replaced with a rebuilt. It is limited slip not posi. Anyone have any other ideas?

[38Chevy454]

[ QUOTE ]
Anyone have any other ideas?

[/ QUOTE ]

Pray a lot that it holds together http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

Seriously, if it clunks when going from forward to reverse then it is freeplay. Freeplay could be either from the rearend gears or U-joints. Like yorg said, a small amount of freeplay in the axle can translate to a perceived lot in the driveshaft. A slipping posi unit should not make it have any different freeplay.

I agree that it would be a good idea to open that cover up and look at the pieces inside for any strange wear. Check or just replace the U-joints.

[porknbeaner]

BG
We run one behind 400+ for about 3 years in a 2,800 lb. vehicle. Lots of 11 seconds runs and highway miles.
I was impressed that it held up at all.
When we pulled it down I had noticed a lot of play at the axles (early 1/2 turn) and times were starting to drop off by tenths.
Chipped gears, pinion and carrier bearings shot, and one trashed axle bearing.
I don't recall ever experiencing slippage when hot, but I'm not sure that I understand you discription. No fault of yours by the way, just old and empty headed http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif
That take a better beating than I ever expected, but like has already been said, I would drop the inspection plate off and get a good look.
Make sure and drain the gear lube into a clean pan so you can guve it a good look also.
Luck

[bustingear]

I run a 350 with auto powerglide. U-joints have been replaced. I have had the cover off some time ago and did not see any obvious signs. Perhaps the beraings are shot?

[gofast62]

bad clutches in the posi unit! had the same problem in a firebird, replaced the little clutches, added new posi trac oil, all fine.

[bustingear]

This is not a posi unit. Only one wheel drives????

[Stevie G]

So....what do you mean by "When hot, it slips a little" ?
Gears don't slip, Torque converters do....Bands and cluthes in transmissions do. I've seen freash rebuilds that slip. Bad day in the shop, dropped the inch pound torque wrench and screwed up the calibration. Mucked up the valve body and it leaks (When hot). Just my 2c (And worth every penny).

[bustingear]

OK well forget the word slip. More like hesitation and like brake drag. That is what it really feels like.

[lesabre59]

I'm currently finishing up on my A-hole, I have the same 7.5 10 bolt, but i am going to put in a Powertrax Posi Unit from Richmond gear, I've heard nothing but praise for these units and you only have to remove your spider gears and slip the unit in, no fussing with anything else. I'll keep ya posted on how it works out.

[Rocky]

The way the brake parts attach to the backing plates on those things, I wouldn't be surprised if you do have a brake problem. I've had them in the past and I have one now under my astro van. Might want to yank the brake drums to see if you have broken a return spring or anchor pin...
BTW, I ran one of those 7.5" rears under my old chevy sedan delivery with a strong running 406, 4 speed and never broke it. The guy I sold the car to managed to scatter the 4 speed but the weeny rear end lived to fight another day.