Rear differential leaking

[unbrokenchain]

The chassis service manual simply lists the axle torque specs based on weight ratings has no mention of brand name except on the Eaton limited-slip. I'm just assuming that HO72 is the 7,200lbs whereas HO52 is 5,200. Brakes/lug patterns are obviously different between the two but sounds like RedRoad has a handle on the internal difference(s).

Mike16, I actually siphoned the fluid out with a squeeze pump so I didn't have to mess with the gasket.

[RedRoad]

To drain the gear oil you just need to remove one of the bottom bolts, either the cover or carrier side as they are both through holes. Its best to remove the cover to inspect AND get all the sludge out of the bottom of the housing. You will be surprised how much crap is in there.

The two gaskets are still available. One is a thin paper type (carrier to housing) while the other is regular gasket material (cover to housing). As mentioned earlier use the gear oil specific RTV for no leaks

http://www.rockauto.com/catalog/more...nid=528&jpid=8

http://www.rockauto.com/catalog/more...nid=528&jpid=2

Here is a list of recent part numbers for the HO72

All the following parts were available at AutoZone, Oreilys, and Napa

Hub Bearings

Inner KD11786y
Outer KB111630z
Seal 2081
Axle flange seal 55350

Permatex Gear Oil RTV 81182


Center Section

Pinion Seal 411330n
Repair Sleeve 99259
Retainer Seal 3758222
3rd member to housing seal RDS5090
Cover to housing seal RDS5088


Brakes (1972)

Wheel cylinder Left BHH WC49680
Wheel cylinder Right BHH WC49681
Wheel cylinder repair kit BHH WCK13620
Shoes BB248
Rear Hose BH 36684
Drum BBR 2079DGS

[Andy4639]

If you have one of these like on mine you don't have to take it a part to check the gears! Ha.

[unbrokenchain]

Whoa, did you make that? Probably would be terrible for the diff, but would be sweet to put a little tritium in the fluid and watch it at night...

I'm going to attempt this myself, have decided to rebuild the wooden bed anyway, so I figure I might as well do both at once and have the bed out of the way for maximum accessibility to the diff.

[bollybib]

Posts 28-33 in my Project thread describe my experience replacing the pinion seal on an HO52 that you may find useful.

[Andy4639]

Originally Posted by unbrokenchain

Whoa, did you make that? Probably would be terrible for the diff, but would be sweet to put a little tritium in the fluid and watch it at night...

I'm going to attempt this myself, have decided to rebuild the wooden bed anyway, so I figure I might as well do both at once and have the bed out of the way for maximum accessibility to the diff.

If your talking about the diff cover No! I bought it from Clear gear covers.
Here is the link I did on the install.

http://67-72chevytrucks.com/vboard/s...d.php?t=519400

[BCOWANWHEELS]

I,d jerk that old style ho52-72 out and put in a new style 14 bolt if it was me. those old rears don't have parts support anymore.

[unbrokenchain]

Have to say, that pinion nut is a bear! I broke a 3/4" drive breaker bar, even bought a compressor and some air tools, but the 3/4" drive impact wrench that's supposed to go to 1,000 ft/lbs wouldn't even bust it. I put the driveshaft back on and drove it to a local shop who will tend to it on Monday. Hopefully they've got something powerful back there!

Hey, at least I've got air tools now.

[BCOWANWHEELS]

please that rear has run dry,junk it and install a modern 14 bolt. its basically a bolt in if you have leaf springs and theres tons of them around for 2-3 hundred bucks. look on craigslist

[unbrokenchain]

I've actually found some decent support for parts at Asheville Powertrain, but if I have issues after the seal is replaced then that'll likely be the plan. Til then, though, I'm still of the "if it ain't broke..." mentality. The differential wasn't dry inside, the oil was just well below the level where it should have been. Have some rear frame repair to tend to, so it might be a while before I build the new bed. That'll allow me to keep an eye/ear on the diff. a little better once it's back on the road.

[mike16]

support is available. you just gotta go a lttle further than your corporate franchise auto parts store. 14 bolts are good but not everybody runs a leaf spring rear, which has nothing to do with logistical support.

[unbrokenchain]

Well I got the truck back from the shop, no more leak! Seal from PartsGeek was not the right one, not even close. Guy that did it was able to read the number off the old seal, Asheville Powertrain had it in stock. Happy about it, only thing is, they definitely messed with the "do not mess with this bolt" bolt. What should I do about it?

[RedRoad]

http://67-72chevytrucks.com/vboard/s...d.php?t=177514

Originally Posted by Ridgeback

MrBinAz

Following is the adjustment procedure for the ring gear thrust pad, taken from the Chevrolet Chassis Overhaul Manual. If you post your email I can also send you a picture of Figure 51 referenced in the adjustment procedure.


RING GEAR THRUST PAD ADJUSTMENT
(5,200, 7,200, 11,000, 15,000 and 17,000 Lb. Axles)
1. Inspect bronze tip of thrust pad and if worn install a new
one.
2. Install thrust pad and tighten screw until bronze tip
engages back face of ring gear while rotating gear.
3. Back off screw one-twelfth (1/12) turn and tighten lock-
nut to specifications (fig. 51).

NOTE: Make sure screw does not turn during lock-
ing process. This adjustment provides .005,, to .007”
clearance between thrust pad and ring gear face.

[unbrokenchain]

Thanks RedRoad! Hard to work the search function when you don't know the name of the part. Ring gear thrust pad. Awesome.