The Stovebolt Site Forums The Shop Area Driveline Eaton HO72 pinion nut torque ?

I replaced the pinion seal on the HO72 third member I bought that has the 4.10 gear ratio. It is out of a 1972 C20. Going by the service manual for a 1972 C20 truck the pinion nut torque spec is 220lbft but I had to go up to 230lbft in order for the cotter pin hole to line up with the nut. Am I in any danger running the pinion nut 10lbft of torque more than what is required?

Check the turning torque required to turn the pinion gear with an inch/lb. torque wrench. If it's not above 20 in/lbs. or so there shouldn't be a problem with a slight amount of extra pinion nut torque.
Jerry

No. That rear end uses a spacer between the brgs. That is the normal procedure for tightening on the HO72 & HO52 rear ends.

The last spec I read on one of these talked about a minimum torque of 160 ft Lbs and a maximum of 280. the idea was to go to 160 and then keep going until the pin hole lines up.

I’m working on the same swap right now in my ‘49. I have the third member out and I have cleaned the housing of the almost 70 years of sludge. Aside from replacing axle flanges and cover/differential gaskets, is there anything else I should do? I’m planning to stay away from replacing lots of parts on this.

My replacement is caked with grease and dirt around the yoke. I’m hoping it is not a bad seal. If it is, how difficult of a swap is it. And does the third member have to come out of the housing to do it?

Not a bad deal to change, just work. But you do want to have the third member mounted in the housing (and it stays in the housing while changing the seal). It's a bear to break the pinion nut loose. I made a wrench that slipped over the pinion yoke with the free end sticking under the leaf spring to keep things from spinning while I used a 3' or so long cheater on a 1" ratchet. Also had to thin the walls of the socket I used on the bench grinder so it'd fit onto the pinion nut, you'll see what I mean. I used white marking paint on the castle nut and flange to ensure that on re-installation, I tightened it to the exact same spot.

good deal. I guess I wanted clarification that I could change it w/o dropping the third member again. Looks like I can. looks like Loosing the pinion nut isn't easy any way you slice it. At least with the pumpkin mounted its one less thing to try and keep from moving around

The best way to handle the pinion nut is a 3/4 drive air impact, or a stout 1/2 in. After you remove the yoke you need to remove the flange, held on by 5 bolts. It has a thick cork gasket behind it. The seal is in the flange. If the gasket is not available you can use a thick coat of RTV.

An impact is common for this repair, and I've used one... but to avoid hammering the gear teeth I much prefer holding the yoke and using a long handled ratchet on the nut (or torque wrench for installing). It's also near impossible to properly torque the pinion nut with an impact, at least the "torque" is just a guess, even if an educated one.
One way to hold the yoke shown above, other people use a large pipe wrench, but that can damage the yoke.

Try one of these
Pinion yoke holder tool, to remove or torque pinion nut http://www.ratechmfg.com/Yoke%20tools.htm

Also works for drive flange on back of transmission, and fits many other vehicles and applications.

Here's the shop manual for servicing these axles.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0410.htm

I bought a 4 foot aluminum pipe wrench at a pawn shop for pennies on the dollar, and ground the teeth flat to avoid damaging driveline yokes. Since Rigid sells replacement jaws for big wrenches, I didn't do any permanent damage to the tool. A 3/4" drive breaker bar with a 3 foot cheater pipe and a modified socket handles the nut.
Jerry

I also have a 4 foot iron pipe wrench I got at an auto wrecking yard in Bakersfield for $5. in the '70's, haven't worn it out yet, works great for holding U-joints.

Ed