Re: Tuning the Posi Unit
Flame Dry
POR 15 Base coat
Flame Dry
POR 15 Base coat
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Preparing the Case
Final Coat
Interior Case Prep NextComment
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Re: Preparing the Case
We are now working the inside of the case prior to installing gears and posi unit. Gary's comments:
"Hi Jack
Here I final prepped the housing. You can see there in the ready pictures the inside didn't look so good after etching and rinsing. It was really only minor surface rust but I cleaned it up good with a wire wheel.
The holes were all chased. The pad holes were bottom tapped and countersunk, this means a bottom tap was used to cut new threads to the bottom of the holes. The factory used a starter or plug tap and the bottom threads don't always get a full tap. The bolt may not fully engage the threads so I know now the hole is fully threaded beyond the length of the bolt. The reason to countersink the holes is to cut the lead- in thread to prevent it from pulling when the bolt is torqued. The same process used on head bolt holes. All the oil passage were brush, washed, and blown clean with compressed air."
Rusting Before picture
Wire Bush
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Preparing the Interior of Case
Chase holes
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Re: Preparing the Interior of Case
Radius Edges
Cleaning bores
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Re: Preparing the Interior of Case
Cleaned and ready to go
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Replacing tail shaft bearing with tranny still in car !
I had removed the transmission last week to both adjust the linkage and to replace the rear seal and bearing. I did not want to take the case apart and in one of the recent posts, John Z mention a tool that would allow you to change the seal and rear bearing while the tranny was still in the car. I located the tool on E-bay and although my tranny is out of the car, I left the shift on to show it can be done .
My old slip yoke had 300,000 miles on it and it shows it.
My new slip yoke and balanced drive shaft
The tool to extract the rear bearing , with seal removed
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Re: Replacing tail shaft bearing with tranny still in car !
Close up of tool
Rear Bearing , the tool slides in just like a yoke
I use a hose clamp to compress flanges of tool , edges grab bearing
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Run out in Posi Unit - Setting Lash
Gary Ramadei is putting the final touches on the rear end he is building for me. He discovered excess run out in the posi unit. Here are his comments and process to reduce run out to his specs.
Hi Jack,
So as I mentioned yesterday there was a wide range of lash in the setup. I wanted to see if it was in the gears or the posi case. I removed the ring gear from the posi and checked the bare posi in the housing. I checked a few places; the posi flange where the RG mounts, the case OD where the RG ID is press fit, and the flange OD. I found the case OD was good with only 001" or less runout in it but the flange had 006" runout and the flange OD had 008". The flange OD doesn't matter but the case OD & face do. I set the posi up in the lathe using a small 4 jaw chuck to dial in case OD as my reference. I dialed the case OD to less then 001" and rechecked the flange run out in the lathe and it was out 006". I faced the flange 005 in small passes and turned the flange OD. In the lathe they were both 0 but I knew it would open up in the housing because it will be referenced off the case bearings.
"I found the caps were loose on the bearing races and set them up to 001" gap. Then I installed the bare case and found the flange runout 002 which is good. The case OD is still 001 and the Flange OD is under 001". I was able to keep the case bearings installed without issue. The lash is now within 002-003 compared to 006 before. I couldn't do a pattern test because I have to let the Loctite setup on the RG bolts again. Next up I will check the pattern to see how it looks. I did radius the edges of the teeth on the RG, this is an old blueprinting trick.
I will see how the pattern looks on Monday."
This video is an example of what he did to my unit. Just click on it
Pictures
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Re: Run out in Posi Unit - Setting Lash
On milling machine
Caps
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Run out in Posi Unit - Setting Lash
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Re: Run out in Posi Unit - Setting Lash
Here are more photos of the build of my rear end by Gary Ramadie and his comments on Pattern.
Hi Jack
Here is the pattern. Now what you will see is the pattern is center to toe, which is how these gears typically set up, unlike "textbook" patterns which are perfectly center on the tooth. What I go by is the pattern being equal in length and somewhat uniform. Attached you will see the Drive & Coast sides of the teeth plus the lapping pattern that is on the gear out of the box- which I call "new pattern". Some gears do not have this but US Gear always does and I like to reference it since it may show how the gear set was lapped. In this case you can see the pattern is center to toe as well only a little high. Setting up this gear set it followed "suit" and the Coast side is center to toe. You will se in my pictures the lengths are equal. Now even though these are final lapped they are never uniform from one tooth to the next. Some may show a full pattern, the next one may be center to toe. I have seen them with one tooth tapering high and the next tapering low. This is where a lot of guys get caught, it is a time consuming process because each pattern change requires break down, cleaning, reshimming, reassembly, then testing. Many cycles to dial them in. Different ratios setup differently but it call comes down to how they were machined and lapped to start. Some new patterns are center on the coast and center to toe on the drive. The rotation is smooth with no binding or noise using a handwheel setup.
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Pattern Rear End Build
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Re: Pattern Rear End Build
Almost done, more comments from Gary.
Hi Jack
Here I fit the new ( rebuilt) Lone Star standard axles. With a common built posi with the springs and plates you would just pop these in with the snap ring and that's it. I have seen rebuilt diff's with axle endplay over .100"!
The tuned posi requires the axles to be fit most of the time, the last diff I did they fit perfect but just about all tuned posi's will have -0- endplay or you might not even get the snap ring on. So I set them up in the surface grinder and grind off 005-010" from the hardened face and set the end play to 005-008". This varies because the spiders are not a fine machined gear so they might be a little different through 360*.
Going back to the posi tuning, this is important to get right otherwise you will issue with the axle gap in addition to the posi not working correctly.
So here it is, all I have to do is fit the cover, shoot a touch coat of paint and crate it up for you. Tomorrow I am off so I will be at it on Friday and have it on the dock for pick up on Monday, you will have it on Tuesday.
Any questions?
Thanks
Gary
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Rear end update
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