Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

John,
Just curious here, is there a GM part number on the ring gear and the nose of of the pinion gear that you can take a pic of?
Lmk thx

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

I also have a 5.38 ratio here , but its in a housing buried in my parts shed
so cant get pictures for now .

John

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

I didn't see any but will check again and get back to you if I find some .

John

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

I suspect that you may have a gear set that was made by aftermarket company some time ago to fit into the Eaton 3rds.
Or it could be a GM Canada thing, whereby there were definitely differences in production and equipment.
Having a GM part numbers would clear up any confusion on being original or aftermarket.
Thanks

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

I'm confused.

I have a SRW H072 in my C3500, So do I just get the backing plates from a 14bolt ff and the drums, then take my hub/drum, separate them, put the new drum and my old Eaton Hub together, swap out backing plates and brake parts, and re assemble?


I am confused if I reuse my Eaton hubs, or if I have to do some kind of magic to make the 14 bolt hubs fit my Eaton spindle......

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

From my understanding you are good to go on the SRW axle. I am geared up to try the swap myself in the near future. My donor axle has slip on drums though. Fingers crossed and good luck.

On a side note. Alot of dual rear trucks came from the factory as SRW and are dealer converted to duals. There is an actual RPO code for it. I have one of these trucks in my yard right now but the SPID is missing.

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

To make sure I have this straight, either bore out the Pre-70 hubs to accept the bigger 9/16 14 Bolt studs, or use longer 1/2 Pre-70 studs? Was there any issues running the smaller studs with the 14 bolt drums? Does the clamping force of the wheel being torqued down hold the drum in place and not slide fore or aft depending on the direction the wheels are turning upon applying the brakes?

I have the backing plates, just need to get the drums, shoes, hardware kit, and lug studs. In my research I swore I read in a thread on this subject that 14 Bolt hubs were required, and that with some creative interchanging of inner bearings and races, that the 14 bolt hubs would work. I then re-read this thread exclusively, as I cannot find the other threads I previously found on the subject, and discovered 14 bolt hubs only work with some machining to accept the Eaton inner bearing race. I did buy some 14 bolt hubs, but will most likely use the Eaton hubs for my swap to 14 bolt brakes.

Any information you guys can provide on the subject that I am missing will be much appreciated.

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

I bored a set of hubs out with a good drill. The metal was actually pretty soft. Then I installed the larger lugs. It was all pretty easy. I haven't run them yet. That will be part of my upcoming swap. I want to set up a rear to be able to run duals but be switchable back to SRW eventually. I need a K30 for a few months.

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

That sounds easy enough. Did you use a drill press? I don't have one, but may be able to use someone else's. I'd hate to have lug studs all crooked:lol:

This is all going in the '65 C20 in my avatar. I discovered in my parts truck's HO52, that it housed a 4.11 3rd member. I went to move the sometimes daily driven truck the other day to remove the radiator for it to be cleaned and sealed, when my clutch decided to act up. I have been wanting to swap in my SM420 and Ranger OD, but have been enjoying the current setup in the truck. Well, if I have to remove the transmission to work on the clutch, a trans swap is in order, along with an upgrade to the HO52. I swapped in front disc in November 2015, so the braking is much improved, but now for a few more upgrades, and more modern 13 inch brakes will be a nice addition.

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

I used my cordless drill after my good drill finally died. I did chuck them in a vice though. It went quick and they came out straight. I mounted the rims with no problem. I did this with a DRW rear but I am going to decide which axle to put under the K20.

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

Read in this forum somewhere (maybe even early in this thread) that the 3.90's were made for the NAPCO 1/2 ton conversions. If you have ever seen one, they are really strange looking as they retain the small 1/2 ton rear, with stock 3.90 gears, but use a modified Eaton for the front, so you have this rear that looks like it came out of a car, then a massive HO52 up front with 6 lug wheels. The 3/4 ton conversions look a lot more normal as the front and rears are both matching Eatons (with the usual 4.56 gears)
So that really makes sense why the 3.90 exists, and is so rare. I don't think anybody has ever found evidence of Chevy offering it as a RPO (I of course could be wrong on that point). NAPCO must have had them custom made for their conversions, and then probably they or the manufacturer had some others they sold as parts for the aftermarket.
This is the best theory on the subject I have come across, and it makes sense to me. What do you all think? Love to hear other opinions on this.
Tom

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

The 1/2 ton NAPCO conversions used the Eaton HO32/33 both front and rear. That is what came stock in the '55 second design thru 1962 in the 1/2 tons They look just like the HO52/72, just smaller. The 3.90 gears were the most common gear found in the HO32/33's.

Re: Eaton HO72/HO52 vs. 14 Bolt FF
 

[QUOTE=jbclassix;5512266]Interchangeability... Sop far, only the brakes are interchangeable between the 14 bolt and the Eaton. I have seen a lot of requests for part numbers and how-to's for the Eaton brakes. Well, here is my how-to rebuild the brakes on the HO72 and HO52. NOTE: for the 71 and 72 HO72/52 axles this is a direct swap. 70 and earlier use smaller wheel studs and will require a hub swap, or the holes on the hub to be enlarged.


So if we were to go to, say, Napa and try to buy a backing plate, shoes, wheel cylinders to perform this swap What year would we ask for? 1973? 1974? 2WD or 4WD K20, or k30? or would any 14bolt 1973 -87 all work the same. I have a 2000 k2500 with a 14 bolt with drums would all the parts from it swap over? Seems like somewhere along the way the e-brake hook up is going to be different and so on.