Another ‘65 C20 14-bolt conversion
 

The old OE 4.57 HO52 Eaton rear end in the truck had been howling and leaking for quite some time. So I finally decided to do something about it. Also I also wanted to change out the gears to a more gas friendly 4.10 ratio. After a bit of research I determined that I could find a complete 14-bolt corporate GM 10.5” full floating (FF) rear axle with the gears I wanted for much less than getting a ‘new’ used third member with 4.10 gears for the Eaton. I decided on the upgrade. I found a low mileage donor FF axle from a 2000 C3500 single rear wheel (SRW) with a 10.5” ring gear and 4.10 ratio for $275 at a local junkyard.
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Initial inspection of 14-bolt FF 10.5” axle; start the disassembly and cleaning process

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One of the great features of the newer 14-bolt rear end is the removable brake drums (without having to remove the axle shaft and hub).

Apparently somewhere around 1998 GM stopped producing this axle and it is now made by American Axle Manufacturing (AAM). Additionally the model year 2000 was also the last year of rear drum brakes, 2001 and later went to disc. Contrary to the 14-bolt bible on billavista.com (the definitive source of information on these axles) the distance between wheel mounting surface (wms) to wms on this particular axle was 65-5/8” instead of the ‘standard’ 67” for the SRW. This was a bit of a disappointment since I wanted to match the track width of the front axle which is 67-5/16” (’65 control arms with ’71 spindles).

Re: Another ‘65 C20 14-bolt conversion
 

After removing and cleaning the hubs, the first order of business was to replace the stock M14-1.5 metric wheel studs with 9/16-18” studs to match the front. Chevy went to metric wheel studs on 88-up C/K trucks. I was able to find Dorman 610-194 wheel studs which are 9/16-18 x 3.5”. These studs are about 5/8” longer then the M14s and should allow the use of 1/2” wheel spacers. I really dislike the idea of using wheel spacers of any kind but I wanted to get the rear track width closer to that of the front and figured the extra inch would help meet that goal. The knurl diameter of the Dorman stud is 0.621” which required drilling the hubs with a 39/64” bit.

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Rusty metric studs (right) replaced by new SAE studs (left).

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Removal of 14 bolt leaf spring perches, shock mounts and swaybar mounts from axle tubes with cutting torch.

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Removal of the worn out Eaton full floater from truck. Note custom swaybar attached to axle tubes.

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Plywood & 2x4 jig to transfer trailing arm perch location, spacing and pinion tilt angle of the Eaton axle to the new 14b axle. I got this method/idea from other members on this site who have done similar conversions.

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Eaton pinion angle captured by homemade angle-finder.

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14 bolt axle now has correct trailing arm perch location, spacing and pinion angle for the Chevy truck coil spring rear suspension. New spring perches for the 14 bolt axle were purchased from John at Custom Fab (Captain Fab) @ dragtrucks.com.

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Perches tack welded in place to lock in measurements. Note washers and bolt heads in the U-bolt holes of perches – these were used to ‘record’ the U-bolt hole locations of the factory Eaton axle.

Re: Another ‘65 C20 14-bolt conversion
 

I installed the trailing arm reinforcement kit from Ecklers Trucks part No. 121076. This kit consists of 1/8” thick weld-on plates for top and bottom of each trailing arm and new and U-bolts. It was also supposed to come with the replacement polyurethane bushings (Energy Suspension part No. 3.3123) and replacement 3/4” pivot bolts. Unfortunately they sent the wrong bushings and no bolts. It took over a month of calls and emails to get them to send the correct bushings. They never did send the bolts. Classic Performance Products also sells the same trailing arm kit and I would imagine they may have better customer service…
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https://lh4.googleusercontent.com/-5...MG_3048-sm.JPG

Re: Another ‘65 C20 14-bolt conversion
 

I made the panhard rod as long as possible by locating the bracket removed from the Eaton much closer to the right side backing plate than the factory location. This was to help reduce lateral excursion as the suspension cycles through its travel.

https://lh4.googleusercontent.com/-9...MG_3093-sm.JPG
New adjustable panhard rod was made from 1-1/8” x 1/4” wall DOM tubing and forged steel 5/8” 4-bar poly rod ends from Speedway Motors (speedwaymotors.com).

Trial fitting of new axle onto the trailing arms; tack weld panhard rod bracket and overload spring pads onto axle tubes.
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Overload springs were something I found from a junkyard years ago (I forgot the application) and were sized to contact the axle when carrying heavy loads. Seemed to work pretty well so I decided to keep them and weld 3/8” landing plates on the new axle tubes to accommodate.

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Axle position near full compression – main springs removed, overloads contacting landing plates

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All welding and painting complete, axle now ready to install in truck

Re: Another ‘65 C20 14-bolt conversion
 

Another discrepancy from the 14 bolt bible was that the pinion yoke on this axle was NOT centered with respect to the housing & backing plates. It was offset about 1.5” to the right which resulted in a compound angle for the aft section of the 2-piece driveshaft. Although this is not ideal, the resultant angle on the aft shaft U-joints was well below the minimum for vibration-free operation.

Indecently the pinion yoke to axle centerline distance of the 14b is only 1 inch greater than that of the Eaton; this would allow the use of the stock driveline (assuming there was enough travel in the slip joint). Both axles use the standard 1350 style U-joint. However I wanted to upgrade the driveline anyway since I had wimpy 2” diameter tubing to something larger, so I found a later model C3500 2-piece driveline from a junkyard with 2.75” tubing. This required shortening of the aft section of driveline to 35” and re-balancing. New U-joints (Moog 331) and carrier bearing (Timken HB88107A) were also installed.

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Final installation of trailing arms, axle, driveline, panhard rod, shocks backing plates and hubs with new hub seals (National 2081)

Yet another area of internet misinformation on the 14b FF axle is the wheel bearing preload adjustment procedure. Most unofficial references I found, including the 14 bolt bible said to torque the wheel bearing hub nut to 50 ft-lbs and you’re done. I looked up the actual procedure in the GM factory manual for the 2000 C3500 and it said the following: “Tighten adjustment nut to 50 ft-lbs while rotating hub and drum. Back off 1/4 turn and tighten to 13 ft-lbs. Align nut slot with closest keyway, insert key, retaining ring and axle.” That last step of backing off is essential for proper wheel bearing preload. Other year applications back to 1973 have similar procedures, all beginning with torque to 50 ft-lbs, but ALL have the follow-up step of backing off to some degree and minor differences in final adjustment depending on the type of locknut style the axle has. BIG difference from just torqueing to 50 ft-lb and calling it a day…

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Final assembly of main springs, custom spring spacers, brake shoes, brake hardware and axle shafts

Re: Another ‘65 C20 14-bolt conversion
 

Connecting the emergency brake to the new axle required some creative jury-rigging. The e-brake cable housing on the older C20 has a bolt type flange to connect to the backing plate whereas the AAM axle uses a circular spring clip which inserts into a hole in the backing plate. I ended up removing the spring clip end of the late model cable housing with a cutoff wheel and grafting it to a new C20 cable housing using JB weld and a short section of heater hose. Then I was able to use the late model cable insert and spring, cut it to the proper length and crimp on a new ferrule.

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Model year 2000 C3500 e-brake cable file photo

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Cut the late model e-brake cable to length and crimped new ferrule to terminate

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1972 C20 cable housing and clip end from 2000 cable housing joined with JB weld and heater hose

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Final assembly of axle in truck complete – panhard adjusted for proper rear alignment

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Ready for wheel spacers and tires

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Rear brake adjustment and bleeding complete – ready to hit the road!

Re: Another ‘65 C20 14-bolt conversion
 

Nice work; looks like a real nice truck, too.

Words cannot begin to describe my feelings about jackstand & cinderblock mountain, though!

Re: Another ‘65 C20 14-bolt conversion
 

Nice writeup :thumbs:

The 4.10's with the NV4500 should make for nice highway cruising. What size rear tires are you running? I'm curious as to what your rpms are at 65-70 mph.

Re: Another ‘65 C20 14-bolt conversion
 

x 2

Re: Another ‘65 C20 14-bolt conversion
 

Excellent write-up and photos. It really goes to show: there's a lot of information on the internet, but not all of it is good! Nice job tracking down the right bearing preload procedure...

Re: Another ‘65 C20 14-bolt conversion
 

Thanks

Yeah the redneck ‘Jack stand cinder block mountain’ technique has fallen off the OSHA approved list (no pun intended).

Re: Another ‘65 C20 14-bolt conversion
 

Thanks!
And also thanks for providing the excellent spring perches - much cleaner than trying to re-use the originals.

Tires are 235/85R16s which are about 31.8” in diameter. 70 mph is about 2200 rpm in 5th – see graph below. Each green line represents the RPM to MPH relationship for each forward gear.
https://lh3.googleusercontent.com/-3...520Ratio-1.jpg

Re: Another ‘65 C20 14-bolt conversion
 

Thanks – yeah I became much more aware of taper bearing preload after my pinion bearing mistake. 50 ft-lbs just seemed way too tight…

Re: Another ‘65 C20 14-bolt conversion
 

Forgot the section about the pinion seal:

The pinion seal on the 98 and up AAM axle is a two piece deal; the outer seal which goes into the diff housing and the inner seal or yoke sleeve which is pressed on the yoke. All aftermarket vendors (Napa, Autozone, Rock Auto, etc…) did not have a listing for the inner seal. Curious, I went to the stealership only to learn that this inner seal is not available by itself; it can only be purchased with a new yoke for $175.00! I laughed out loud and left. After a little research on the web I found a complete seal kit with both seals, crush sleeve, nut and washer for $39.09 from Ft Wayne Clutch: PN 74020011.
https://lh4.googleusercontent.com/-o...gm_sealkit.jpg

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Pinion bearing housing with outer seal, pinion with new crush sleeve and yoke with inner seal

Replacing the pinion seal required more work/skill than I had initially thought. I was planning just replacing the seal and re using the original crush sleeve. Unfortunately I went a bit overboard on torqueing the pinion nut upon reassembly which resulted in too much preload on the pinion bearings (~30 in-lb). So I had to get a new crush sleeve and try again… The second attempt was much better at 7.5 in-lb of preload. Fortunately the 14b axle has a removable pinion bearing housing which makes this job easier.

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Measuring pinion bearing preload torque with beam-type torque wrench

Re: Another ‘65 C20 14-bolt conversion
 

https://lh5.googleusercontent.com/-5...MG_3239-sm.JPG
Giving the ‘new’ 14-bolt a workout with 3500 lb of river rock…

Re: Another ‘65 C20 14-bolt conversion
 

Post number six, does that say "Electric" on the back of that VW ?

And, your latest picture is a beauty. I hope you appreciate the nice scenery where you live. It made me think of a recent experience I had. My wife drug me to Vegas for one of her business trips (I hated the city with a white hot passion and will never go back under any circumstances). One day I was standing there looking off into the distance. A local asked me what I was looking at. I told him "the mountains". He said "hmm, I never really noticed them". If we'd have been back in Texas instead of Vegas, I think I could have legally shot him for being so ignorant.

Re: Another ‘65 C20 14-bolt conversion
 

Nice.... No doubt making use of those overload springs :thumbs:
That's the kind of work these trucks were built for.

Re: Another ‘65 C20 14-bolt conversion
 

Yes – I converted a 2001 Jetta to electric drive for my daily driver. It only costs $0.04 per mile to operate. More info at http://www.diyelectriccar.com/garage/cars/253


Thanks, yes I fully appreciate the desert southwest! Some time ago I had to spend 4 months in the Lewisville/Ft Worth area for work – I went through some serious Mountain withdrawal…

Re: Another ‘65 C20 14-bolt conversion
 

After reading your build thread over there, I can see this rearend swap wasn't much of a stretch for your abilities.

Don't take this in a negative way.....Did you build that electric car stuff right there in your shop ? It looked like a lot of jigsaw and drillpress work was done. I didn't see any high tech machinery or discussion about three axis CAD files and other similar rocket surgery. There's guys out there doing half the work with equipment that costs in the millions.

Oh well, I'm off to spend the rest of the day reading about electric car conversions on that other board.

Re: Another ‘65 C20 14-bolt conversion
 

Actually I did the EV conversion at my last house where the ‘shop’ was just the back porch. Since then I’ve moved to a house that has a garage which is where I did the Chevy axle swap.

Fortunately I still have limited access to a machine shop at the University for when I need to use a mill or lathe for hardcore mods…

Re: Another ‘65 C20 14-bolt conversion
 

I've done a little reading on EV conversions and it seems to be within the capabilities of someone with decent mechanical abilities. If I had the funds I'd give it a try.

Re: Another ‘65 C20 14-bolt conversion
 

Yes, especially an older vehicle where you don’t have to worry about integrating the new electronics with the vehicle computer modules…

Re: Another ‘65 C20 14-bolt conversion
 

I see you used the plywood jig like I did. :)
I seen so many threads where they did all the work under the truck. I didn't want to be crawling in and out from under the truck. The jig makes everything easy to line up - like the perches and setting the pinion angle.
Good Job!

Re: Another ‘65 C20 14-bolt conversion
 

Thanks!

Yeah the 14b conversion thread I got the idea from had the 2x4s nailed to the shop floor (which was wood). The plywood worked well but was a bit warped so I had to weight it down with CMU blocks...

Re: Another ‘65 C20 14-bolt conversion
 

Looking at your picture in post 5. I believe you have you Primary and Secondary shoes reversed.