'64 Wildcat posi swap

Discussion in 'A boatload of fun' started by 64 wildcat conv, Mar 22, 2015.

  1. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    I finally found a posi for my 9-3/8" rear axle to replace the OE open carrier. Since I am happy with my stock 3.07:1 gear ratio (which actually performs more like a 3:37:1 with 60 series tires) my plan was to swap the original carrier for the posi carrier when I rebuilt the rear suspension and axle, which I started back in February. Once I removed the axle shafts and rear axle from the car the real work began. First step was to clean the center section casting to remove 50 year old undercoating and a little dirt/oil from a slight leak at the pinion seal. Since I am having no issues with the pinion bearings I chose to only change the seal and leave the pinion be. This would make the posi swap easier too as I would only need to worry about adjusting the carrier shims to get the correct backlash. After removing the 10 or so nuts holding the center section to the axle housing I had exposed the belly of the beast:
    OE gear set.jpg

    My buddy who works at a Meritor R&P plant for trucks says this is closer to a truck axle than a car. They don't make them like this anymore :TU:. Next step, according to FSM (Factory Shop Manual), was to measure the ring gear backlash before disassembly. I used my trusty Central 0-1" dial indicator and found I had .009" backlash, not bad considering new gear spec is .007"-.009" and the car has 105,000 miles.
    OE backlash.jpg
    The next step was not according to the FSM as I did not have the proper pullers to remove the carrier bearing support shafts. I've always thought that necessity was a mother and decided my best bet was to improvise and remove the spider and axle gears from the open diff (be sure to mark their location should you want to reuse them someday) by knocking them out with a long 1/2" drive ratchet extension and large socket. I had to assemble the socket on the extension for the first side inside of the carrier. Once one support shaft was out I was able to just switch ends and carefully drive out the other shaft. This didn't take a lot of force. Use a couple of small (1/2") chisels to slightly open the clamps that hold the support shafts tight. Be carful not to go too far and break the casting. It doesn't take much. You might think that the carrier assembly would drop right out of the center support but not so, the bearings are heavily preloaded and require a special spreader to open the clamps and allow the shims and carrier to be removed.
    This is where I have to rant. The special tools required to service these old axles (and cars in general) are few and far between. There are many sellers on fleabay ond other sites who attempt to sell them at very high prices. It seems that most don't even have the entire tool, but rather a part or two of the tool that may or may not work w/o the other parts. Most will not negotiate. This is the special spreader tool from the FSM:
    FSM shim install.jpg
    One was offered on the internet for a couple hunderd bucks, but it was not complete so I offered them half and they wouldn't come down, so I made my own for less than $100 and an hour or so time. I did find the support tools (T-handle) that simulates the support shafts for a reasonable price from another dealer and they are invaluable for adjusting the backlash. It would be difficult to make these as they have a taper ground on them to fit the tapered bore in the bearing cones. Anyway, I made my own spreader tool using 1/2" rod, 1/2" ID x 3/16 wall steel tube, and four 1/2" spherical rod ends. The idea is to put the rods through the clamp holes and to use the rod ends and tubes to provide force to push the rods outward to open the clamp ever so slightly. All you need is enough to slide the shims in/out.
    Here is the center section with my spreader tool installed and the center section removed (note that I checked the gear pattern before removing the carrier):
    open diff removed.jpg
    Next step was to do a little cleaning on the clamps and to remove the ring gear, clean it and its bolts in preparation to be installed on the posi! Once the gear was ready I again had to improvise as the gear is a snug fit that has to be driven on/off the carrier with a plastic hammer. My 2# dead blow worked just fine. I used longer bolts (7/16 UNF x 2" or so long) to align the gear as the OE bolts will not engage the gear before it gets snug on the carrier. Once it was about 75% seated using 3 long bolts for alignment and a platic hammer to carefully seat it I pulled it down the last 1/8" or so using the OE bolts being careful to alternate side to side as I went around the gear. Once the ring gear was fully seated I torqued the bolts in 3 steps to 70 ft-lbs, per the FSM.
    posi carrier.jpg

    OK. The next step that I forgot to get pictures for is to install new NOS bearings in the posi, the cups in particular. I do have the lower portion of the tool that actually fits inside the bearing cup and has a lip that fits between the cup and the carrier housing. This expands and stays in place when you thread in a 1-1/4"-12 threaded bar. I used a large puller adaptor, about 3-7/8" ID, and extra thick washer and a 1-1/4-12 nut to complete the puller and remove the bearing cups or races. Installing the new ones is a little easier if you freeze the cups overnight and then either drive them in with a hammer or press. I have and prefer a press. I marked the NOS bearing cups and cones to keep them as sets although I have heard this is not absolutely necessary. One thing about these bearings, I researched them and could not find an interchange for them. The bearing cones (the half with rollers) have a tapered bore that mates to the support shaft and helps lock it into position. This is not common. I was lucky enough to find NOS GM bearings for $130 for both. It would be best if you got the old bearings with the posi as new ones are not easy to come by. The ones I removed from my OE axle with 105000 miles looked good and had no free play.

    One thing I forgot to mention at the start, the center section is heavy (at least 75-80 pounds) and awkward to work on. I made a "stand" using four pieces of 3/8-16 threaded rod 14" long and used nuts and washers to actually fastn the whole thing down to my workbench. I pulled it down tight to the pinion flange which helps with backlash measurments and stability. When I need to turn the pinion I raise it a little by adjusting the nuts on either side of the center housing flange.

    Now the posi carrier with new bearings and the OE ring gear is ready to install into the center section. As this is very heavy care must be taken to assemble it into the center section while both engaging the pinion gear and holding the bearing cones in place. Unless you have 3 or 4 hands or a garage assistant you will need to work smart. I keep large, strong magnets handy for these times. Two magnets, about 1" x 2" in size, were placed just over the edges of the bearing cones to keep them in place but yet not be in the way of dropping the lower half of the bearing between the clamps. Also, I used a pice of 1x2 pine laid across the center section just to the right of where the ring gear will go to temporarily support the posi carrier while I remove the magnets. With these two tricks it was a breeze. Once I had the ring and pinion engaged and the carrier to about the right depth I slipped the support tool (T-handle) into the right bearing while holding the ring gear and carefully jostling everything into position. Be sure to use a chisel to spread the clamps just enough to allow the support tool to slide with a little effort. After the right tool was in I slid the left tool in. This allows the carrier to be moved side to side in the clamps. Now you want to set the backlash and measure for shims.
    ready for shims.jpg

    Since I am reusing the original gear set and I did not mess with the pinion bearings I only need be concerned with the backlash and I want to get as close as possible to the original backlash of .009" as possible. I would not recommend changing the pinion bearings unless there is a problem with them or when installing new gears, if you can find them! Setting the backlash is really nothing more than carefully moving the carrier assembly back and forth and measuring the backlash until you get it dialed in. It sounds easy but takes a lot of patience. I got it to .0085" after several tries and then pulled the chisels to tighten the clamps on the support tools. I then rotated the carrier and pinion a few times to measure backlash in different locations, always getting the .0085" reading. Great! Using several loose feeler gauges I measured the distance between the shoulder of the bearing cup and the inside of the clamp as shown below. You want a tight drag but not too tight. Also, you want to leave the feeler gauges in one side when you measrure the other side. I also mic'ed the feeler gauge stack to be sure the measurement matched the added values of the gauges, which they did within .0002". I marked the posi with the measured distance which was .054" on the right and .064" on the left. Now, for the tricky part, you actually want to use shims that are .002" thicker than what the measurement is to preload each bearing .002", so I ordered shims that are .056" and .066". There are several sources online that have the NOS shims. I have a list of part numbers for various thickness if needed.
    posi backlash.jpg shim measure.jpg shim thickness.jpg

    Once the shims arrived I installed them by removing the support tool on the right (don't forget the chisel!) and installed my spreader tool. I spread the clamp just enough to slide the .056" shim in with pressure from my thumb and then centered it from the inside with my fingers. I then reinstalled the support tool and removed the chisel. The left shim was done in the same fashion but you have to spread the clamp a little further to allow the shim to slide into place. Slide the left support tool into place and remove the chisel. Remove the spreader tool. Now lightly tap the support tools inward to seat the bearings while rotating the carrier. Now remeasure the backlash (make sure the pinion does not move). It will likely be greater with the bearings preloaded. In my case it moved the carrier a little to the left making the backlash .0095" instead of the .0085" w/o preload. I was lucky since I was a little less than the .009" original backlash I had to do nothing. The additional .0005" backlash should not be an issue. This may not always be the case but I would tend to set the backlash up a little tight (.0005" to .001") before measuring for shims.

    The next thing is to lube up the support shafts and install them one at a time, tapered side inward (there is a bushing in the inboard side that the axle shaft rides in) after removing the support tools, again one at a time. Seat the support shafts by lightly tapping on them using the support tool and a small hammer. Once both are installed and seated, recheck the backlash and torque the clean and lubed clamp bolts to 50 ft-lbs. That's it!

    I may rent my special tools for this job for a reasonable fee and deposit. Please PM me if interested.
     
    Last edited: Mar 23, 2015
  2. 66electrafied

    66electrafied Just tossing in my nickel's worth

    Cool!

    I've often wondered how a job like this could be accomplished, you made it look easy!

    The one thing I'm not entirely sure of; (maybe I didn't read it right) - I look at the 3.07 posi axle in my Electra as opposed to the limited slip 3.07 in the Wildcat and they look like two totally different housings; did you swap out the whole housing or did you just swap out the gear sets?
     
  3. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    The '66 axles are different. According to what I have seen in the parts books, '63-'65 axles are the same, m/l. My write up would only apply to those years. Basically what I did was swap out my original open carrier for a posi carrier, reusing all parts that were original to my car except the used posi carrier and the NOS carrier bearings. Other new parts used are a new pinion seal and wheel bearings and seals.
    Having or making the necessary tools is a must. It would be easy to do a lot of damage w/o them.
     
  4. 66electrafied

    66electrafied Just tossing in my nickel's worth

    Thanks for the clarification; - I had a suspicion about the tools. I looked through the manual and they have some interesting looking things that I don't have or have the skill to make. The Electra is going to need a total overhaul, it's got some sort of a vibration that I can't diagnose and it's the one component I haven't rebuilt yet. The Wildcat still only has about 120,000 miles on it, and still feels pretty tight. Still; although I'm a good engine rebuilder, I think I'll probably end up getting them rebuilt professionally. For one thing, the rear end oil smell makes me sick; I had a bad experience with the stuff when I was a teenager and still can't go near it.
     
  5. lapham3@aol.com

    lapham3@aol.com Well-Known Member

    '65 was the end of the drop-out 'chunk' (Ford 9" type)and in '66 and forward was mounted integral with the 'banjo' housing. It seems that lots of folks have no desire to do fluid change on these as most I've delt with are neglected. Nice work on the tooling fab
     
  6. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    Thanks. I did all of the fab work with tools most already have in their garage: a die grinder with 3" cut-off wheel and a bench grinder. All of the parts for the spreader came from McMaster-carr, even the tubing and bar stock.

    I'll bet many of these rear axles are neglected because Buick didn't see fit to put a drain plug in them. When I bought my car with 99k miles on it I assume it had the OE gear oil which stunk to high heaven when I pulled the fill plug. The level was a little low at the time so I decided to use a suction gun to remove as much of the old lube as possible (about 1.5 qts) and then refill with fresh oil. I drove it on this until the posi swap. Fortunately there was no unusual wear on the gears or other components and very little residue in the axle housing that shows the GM guys did their homework when designing/building these cars. I was tempted to add a drain plug but at the end of the day did not because at 1500-2000 miles/year it will be a long time until it needs serviced.

    I will post photos of my first burn out when I get her back on the road :3gears:
     
  7. lapham3@aol.com

    lapham3@aol.com Well-Known Member

    When I check one these I pull the cover for draining and verify gear backlash, tooth pattern and general conditions. I'll sometimes use a gasket, but lately RTV-and I see Permatex now has a 'special' RTV to resist gear oils better. Years ago, I picked up a bunch of Lisle magnet fill plugs and use those to pick up ferous that would give an indication of wear.
     
  8. VandaLL

    VandaLL The Buick Life

    Mark, where are the burnout pics?! :3gears: Awesome write up thank you for doing that. I wish posi units were more standard equipment back in the day. My 65 225 is open of course so hoping to convert at some point. Where did you acquire the posi unit?
     
  9. telriv

    telriv Founders Club Member

    The original rear oil was "Whale" oil. That's why it stinks, but is a GOOD oil. Of course not made any longer. There was no spec for changing the oil as it was supposed to last a LIFETIME.
     
  10. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    No burnout pics yet but I know the posi works due to our loose gravel sloped drive. I used a bore scope and found my car has the OE timing chain and sprockets at 106k miles. I am a little hesitant to push it until I get that changed next winter.
     
  11. 66electrafied

    66electrafied Just tossing in my nickel's worth

    Yeah, you might want to get that outta there...
     

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