No spin?

[swamp rat]

On my glove box door the sticker has this listed:

G86 No Spin rear axle.

My question, does this mean limited slip? There is definitely nothing external to lock the diff, Its an Eaton HO72

[Mike C]

It means what it says. Like a limited slip, the no-slip or no-spin, works automatically- there is no external lever or button that needs to be engaged. It is the fore-runner to the Detroit Locker. Jack it up on the pumpkin and put it in neutural, NOT RUNNING, then rotate the tire forwards or backwards and if the opposite side turns in the same direction it is a no-spin. If it rotates opposite, it is an open diff.

I have a '70 GMC parts truck that was factory 4.57 and no spin (Dana 60) but when I pulled the cover off I found 3.73 open. So you never know exactly what your getting with an old vehicle.

[swamp rat]

Originally Posted by Mike C

then rotate the tire forwards or backwards and if the opposite side turns in the same direction it is a no-spin. If it rotates opposite, it is an open diff.

I have a '70 GMC parts truck that was factory 4.57 and no spin (Dana 60) but when I pulled the cover off I found 3.73 open. So you never know exactly what your getting with an old vehicle.

Ok thanks, Just didn't know if it designated limited slip, if i do remember correctly they both do spin forward. Per your other comment, i couldn't agree more

[WIDESIDE72]

Originally Posted by Mike C

I have a '70 GMC parts truck that was factory 4.57 and no spin (Dana 60) but when I pulled the cover off I found 3.73 open. So you never know exactly what your getting with an old vehicle.

I am sure that that gear swap adding quite a bit to the driveability of the truck. Talk about a stump puller!
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[twisty]

Originally Posted by Mike C

Jack it up on the pumpkin and put it in neutural, NOT RUNNING, then rotate the tire forwards or backwards and if the opposite side turns in the same direction it is a no-spin. If it rotates opposite, it is an open diff.

what if only the one wheel you are spinning turns? if i spin one of the rear ends i have quick enough i will see the opposite tire spin the same way, but for the most part if i just casually spin the wheel the other doesnt move.

[SS Tim]

Originally Posted by swamp rat

On my glove box door the sticker has this listed:

G86 No Spin rear axle.

My question, does this mean limited slip? There is definitely nothing external to lock the diff, Its an Eaton HO72

Like has been said it is a locking differential unit that replaced the spider gears inside the differential case. What makes you think your truck has a HO72? HO52 axles were stock for CK20 trucks.

[swamp rat]

Keep in mind this is a uncertain guess gathered from what i have been researching on different forums and i have yet to prove anything out.

The HO72 and HO52 are mainly different by weight designation, and brake size, yet i cant find anything for sure on the brake size. But HO52 i think is rated at 5200 and the HO72 at 7200lb

Some of other stuff other "experts" say like the HO52 only has 2 spider gears Vs 4 for the HO72 dosent seem to pan out ether.

If you or anybody have any info or leads (even better a casting or stamping numbers chart) it would be greatly appreciated.

[SS Tim]

Been doing a lot of research, unless you think the axle has been changed it is probably the factory K20 HO52 (5200lb) axle. The brakes would be 11 x 2 3/4". There was also a Dana 60 (5500lb) usage in the K20s but that is very different looking intergral carrier style axle.
A C30 rear axle, HO72 (7200lb) has a heavier housing and 13 x 2 1/2" brakes on SRW trucks. Often people cite the load bolt that controls ring gear deflection as an indicator but it isn't. Fact is the drop outs are interchangable with the difference being the housing itself, the bearings, hubs and seals are the same. At this point the easiest thing to do is check the axle code and see if it is a K20 or a C30 application. There is no code overlap I know of between the two. But the catch is the carriers are code stamped and not the housings. There is an axle code chart in the parts manual.

[swamp rat]

Would it be safe to say I have the ho-72? There is an adjusting screw on the driver side of the diff plus my rear drums are pretty big, my rims are 16.5 and my drums look to be about 3" smaller plus they have the heat dissipation ribs around the outside. I need to get under it and find some numbers soon. I can't upload pictures now
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[SS Tim]

11 x 2 3/4" C20
13 x 2 1/2" C30

Like I said earlier the load bolt is not a positive tell. The only way to know anything is to decode the drop out. The axle housing would have to be a judgement call based on original installation and brakes.

Why are you wanting this to be a HO72 anyway? The 13" drums are about impossible to find.

[Stocker]

Correct me if I'm wrong.... HO72 always has the load bolt, HO52 some have it and some do not. My K20 has an HO52 with the load bolt, and FWIW the drums are finned.

[SS Tim]

Originally Posted by Stocker

Correct me if I'm wrong.... HO72 always has the load bolt, HO52 some have it and some do not. My K20 has an HO52 with the load bolt, and FWIW the drums are finned.

That seems to be the pattern at this point. If you have a load bolt rear, post up the axle code stamped into it.

[swamp rat]

Originally Posted by SS Tim

That seems to be the pattern at this point. If you have a load bolt rear, post up the axle code stamped into it.

Point me to where i need to look if ya would save me some muck scraping time, Thanks!

[Stocker]

Originally Posted by SS Tim

If you have a load bolt rear, post up the axle code stamped into it.

It's a work truck, not a show truck, and it's a bit crusty underneath. A quick look found nothing. Where should the numbers be?

[SS Tim]

Originally Posted by Stocker

It's a work truck, not a show truck, and it's a bit crusty underneath. A quick look found nothing. Where should the numbers be?

On the top forward section of the drop out.

[Ol Blue K20]

Originally Posted by Stocker

Correct me if I'm wrong.... HO72 always has the load bolt, HO52 some have it and some do not. My K20 has an HO52 with the load bolt, and FWIW the drums are finned.

My drums are finned also.. now for the stupid question what is a load bolt?

[swamp rat]

Originally Posted by Ol Blue K20

My drums are finned also.. now for the stupid question what is a load bolt?

Heres a link, its on the side of the carrier:

http://www.google.com/imgres?q=Eaton...6geaOCTrG0M%3A

[swamp rat]

Originally Posted by SS Tim

11 x 2 3/4" C20
13 x 2 1/2" C30

Like I said earlier the load bolt is not a positive tell. The only way to know anything is to decode the drop out. The axle housing would have to be a judgement call based on original installation and brakes.

Why are you wanting this to be a HO72 anyway? The 13" drums are about impossible to find.

I'm just trying to verify what i have because i want to convert to Disk brakes in the near future, i don't want to order a bracket or kit to find out that a HO-52 and HO-70 may have a different flange pattern. Humm, guess i could have asked/mentioned that a while back huh?

Yea i know 14 bolts are plentiful, I've thought about it a lot, i just want to go this route for now, i figure if i ever decide to convert to 14 bolt i can use the disk setup when i cross over as well if i cant find a 14 bolt already converted.

[SS Tim]

The load bolt is used to prevent the ring gear from deflecting under load at the pinion gear (as in push away). It has a shoe that just floats against the ring gear under unloaded conditions.

[swamp rat]

Originally Posted by SS Tim

The load bolt is used to prevent the ring gear from deflecting under load at the pinion gear (as in push away). It has a shoe that just floats against the ring gear under unloaded conditions.

Thanks for the explanation and pic, any idea what a proper clearance would be on it? i ask because the grease monkey at Jiffy lube thought it was to check the gear lube level, guess he never dealt with antiques before not sure if he messed it up but figure i should check the setting.

[SS Tim]

Originally Posted by swamp rat

Thanks for the explanation and pic, any idea what a proper clearance would be on it? i ask because the grease monkey at Jiffy lube thought it was to check the gear lube level, guess he never dealt with antiques before not sure if he messed it up but figure i should check the setting.

All depends if he just wrenched it down or not.

[special-K]

Originally Posted by swamp rat

I'm just trying to verify what i have because i want to convert to Disk brakes in the near future, i don't want to order a bracket or kit to find out that a HO-52 and HO-70 may have a different flange pattern. Humm, guess i could have asked/mentioned that a while back huh?

Yea i know 14 bolts are plentiful, I've thought about it a lot, i just want to go this route for now, i figure if i ever decide to convert to 14 bolt i can use the disk setup when i cross over as well if i cant find a 14 bolt already converted.

The axle flanges on HO52s and HO72s are the same. The brakes can be interchanges,as the 14-bolts can as well. The No-Spin is a locker,not a limited slip and only came in the corporate rears (HO series). They are Detroit Lockers that GM gave their own name to. The Dana 60s came with the Power-Loc which is a limited slip from factory (if optioned)

[swamp rat]

Originally Posted by special-K

The axle flanges on HO52s and HO72s are the same. The brakes can be interchanges,as the 14-bolts can as well. The No-Spin is a locker,not a limited slip and only came in the corporate rears (HO series). They are Detroit Lockers that GM gave their own name to. The Dana 60s came with the Power-Loc which is a limited slip from factory (if optioned)

Thank you for that information!

I have all the No-Spin pamphlets and i'm fairly sure this is the stock unit, our family got this truck when it was a year old.. I'll find out soon enough

I don't want to open it up until i have all the disk brake parts i need front and rear, as well as a new booster and am ready to do the swap, cant buy it all at the same time so trying to save some coin and then dive in with both feet.

[SS Tim]

You can download workable and searchable copies of both the factory service manual and the overhaul manual here.

http://67-72chevytrucks.com/vboard/s...d.php?t=558016

Really not sure you need rear disc brakes. The kits I have seen either don't use a park brake at all or rely on a poor mechanical design intended for a much lighter vehicle.

If money is tight get your 72 front disc brakes up to as new with some quality pads, rotors, calipers and hoses. They do most of the work even more so on a lightly loaded truck. Then just go through and clean up the rears. Adjusted and working correctly they do a great job.

[Ol Blue K20]

Thanks I'll check it out
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