Thought I would post my progress during changing the gears in my 68 bird (some suggested to leave this work to pros and we will soon find out if that was good advice)
As a side note the reason for the change was there was an open carrier and 3.08 gears, I opted for posi with 3.90, mainly because I want to squeeze the most acceleration out of my weaker 400 until a future upgrade to the HO 400 and M21 trans,
Anyway here's what I have learned so far:
I decided to test the current gear install just to see how good of a job was done, and from what I could tell (on a rearend that was working perfectly fine with no issues) I tested the gear pattern, I will post a pic, I was not impressed from my research both sides were smeared edge to edge, and with barely any backlash measured ( I bought a gauge) I'm guessing that the pinion depth was set wrong.
I also tested the preload on the pinion gear, from some videos I watched people were tightening these with 5' levers and torque amplifiers, I used a lever style torque wrench and turned pinion nut, gauge barely registered. My thought no where near tight enough probably why the back lash was off. I was able to remove pinion nut with minimal effort from impact wrench
I removed the carrier, and boy was it locked in there tighter than [censored]. I tried removing with pry bar, wouldn't budge, I then put some wacks on the pinon trying to push it out, no luck, I finally got 4' crow bar worked in there and may slow progress but got it out. My guess over shimmed, there were two thick ones, not sure size as my battery in my gauge was broke but I will post shim size later, but again from some videos I have seen the carrier should come out a little easier.
That's It for now, please comment on any or all of these issues as I am learning as I go!!
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
If the rearend had 100,000+ miles on it the pinion would not have the preload that people think it should. But that's just wear and tear on the bearings and would spin free. Pinion preload has no relation with backlash unless the pinion nut is backed off, but at that point it would be a noisy oily mess. I would not worry about the pattern on the used gears if it was not making noise it's good. If gears were set up improperly and someone put 50,000+ miles on them you will never get the proper pattern and would most likely make noise.
The way I understand it is that backlash is related to carrier position left and right but if the pinion gear rides deep into the ring wouldn't that restrict movement disallowing proper backlash reading
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
The way I understand it is that backlash is related to carrier position left and right but if the pinion gear rides deep into the ring wouldn't that restrict movement disallowing proper backlash reading
I would agree with that but it based on the assumption that the pinion depth is correct.
What was your backlash measurement? .006 and .010†of backlash is ideal.
Will the posi(saftey-track) carrier fit inside the diff case? I was wanting to put a 3.55 unit in my standard non-pos and was wondering if that will work.
Will the posi(saftey-track) carrier fit inside the diff case? I was wanting to put a 3.55 unit in my standard non-pos and was wondering if that will work.
You would just have to pull out the differential and take off the ring gear and install on the limited slip unit preferably with new ring gear bolts with some red lock tite and. Set backlash to .008 with proper pre load on the differential. This still should be left to someone with experience
It's been a while since I've set up a gear set but have done several in my time. Some thoughts: Aftermarket pinion gears are marked with their installed proper depth. (Distance from carrier bearing split to rear face of pinion gear.) The rear bearing is shimmed to achieve the proper depth. Tapered roller bearings are typically very close assemblies. One can save a lot of work by buying two then grinding the bore of one to be a slip fit on the pinion. This saves pressing the bearing on and off to establish pinion bearing shim thickness. Factory pinion gears are not marked and can be trying to set up. Pinion bearing pre-load is very important. Too tight and and the front bearing will burn. Preload can be touchy to set. Once a crush sleeve is crushed too much, too much preload, they can't be reset. (I've "straightened out" a couple to reuse but don't recommended doing so.) A beam type inch lb torque wrench is required to properly set. Always stone the mounting surface of the ring gear and carrier to ensure there are no nicks or burrs even with new gear sets. Always use new ring gear bolts, install them with red Loctite and properly torque. These bolts transmit all the torque. Gear set up is pretty straightforward but one must understand the assembly and have the proper tools to do it right. In addition to the proper torque wrenches, a test dial indicator and 1" micrometer to measure shims is a must. Access to a hydraulic press for bearing installation is also a requirement.
I feel I have a good understanding of backlash and shimming he carrier, what I am still trying to understand is shimming the pinion. What are you looking for to determine the proper depth?
All tools mentioned are in my possession. And I am planning to remove the old bearings and sand the insides down so I can use them for setting the depth, so I don't have to take them on and off.
Thanks
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
Again what Dennis was saying about Pinion depth, a new set of gears should have a depth measurement on the pinion face. This will be the distance from the face of the pinion to the carrier center line.
I worked with an old machinist to set my gears up a long time ago. He made his own tool for doing this. It consisted of aluminum donuts that bolted in the bearing carrier caps. Then he had a bar that ran through it. The job consisted of pressing the bearing on and off several time to get the shims right. He would measure between the pinion face and the centered bar. Then we had to subtract 1/2 the measurement of the shaft to find the center. I don't know if any of that description made sense but most tools for doing the job are similar.
A used crush sleeve and honing out a extra set of pinion bearings would make the job way less exhausting. There should be plenty of youtube videos on the subject.
I have an engineer guy at work that setup his own gears in his daily driver. He used a fish scale on a breaker bar to set the preload for that 15inch/lbs. The factory service manual is also a great resource.
I myself have a great place in town called Saddler Machine that does my gear setups. I can take them the whole rear all ready to go and it maybe cost a few hundred for the peace of mind. Not trying to discourage you just a warning. I have seen some shade tree mechanic types way screw up a whole rear end gear pattern. I'm talking gears whining really bad going down the road. Once its messed up you can maybe reduce the whine but not completely get rid of it without a new set of gears.
I bought a tool from ratech that sits in the carrier race and sits above the pinion face. My understanding is with this measurement and some math I should be able to obtain the proper shim thickness
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
Please understand, I'm not trying to dissuade you. On the contrary, trying to give you the information to properly install a new gear. I'm sorry, I'm not familiar with the Ratech tool you mention. I have a bar I made up and use a depth mic to measure the distance. Are you going to buy and set up an aftermarket gear set? If so, then setting the pinion depth is very straight forward. The proper pinion gear depth will be etched on the face of the pinion gear. This is the distance from the center of the ring gear to the face of the pinion gear. Thin shims are installed between the rear pinion bearing and the step on the pinion gear to achieve the proper depth in the differential case. Sand or grind open a rear pinion bearing. Slip it onto the pinion without any shims and measure the distance from the ring gear center line to the pinion face. Subtract this dimension from the distance etched on the pinion face and that's the shim thickness required. Without the pinion depth magic number the pinion must be installed, carrier installed to the point of checking the pattern then everything blown back apart again to shim. Pinion depth is somewhat subjective because the only reference one has is the pattern. This is the case when setting up factory gears. Due to this, they are a PITA to set up. If buying a new gear, buy the complete installation kit too. Will have all the bearings, shims, ring gear bolts, etc.
Pictures show an aftermarket pinion gear without rear bearing, a GM gear with bearing and the pinion depth etched on the pinion face. And yes, for those of you paying attention, that is a April 1969 GM 4.56:1 pinion from a 8.875" differential. (And I'd rather build 5 aftermarket sets before expending the effort to put that factory gear into something...)
If using a factory posi carrier, do not use synthetic gear lube. And use the GM additive.
Dennis I appreciate your advice, I am installing a new set of gears, and I bought complete set with new carrier, bearings and install kit. the tool I am talking about sounds similar to what you are referencing. I included a pic sounds just like I was hoping that after making a dummy bearing and using the tool to determine the proper pinion depth the majority of the work will be determining the carrier shimming to get the proper backlash. Sounds like the real PITA would have been trying to determine pinion depth with trial and error. The tool is available for all different rearends I bought the one specific for the 8.5. You can see from pic the idea is the round side rests in carrier race then measure from the pointed end to the pinion face
Last edited by acenho; 02/24/1610:36 AM.
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
That's right, establish your pinion depth then set the carrier. Big Chief is correct, once everything is set, check the pattern. I ran a 4.11 gear on the street for many years. Still running a 3.73 but with now with OD. (ok, I'm not quite as old school as I used to be...) I drive my cars a lot. That 3.90 will make a lot of heat especially when fresh. Break it in gently. I'm a fan of power steering. A tall gear (sustained RPM) and the small PS reservoir will cause the oil to bypass back to tank more than normal creating heat. If you drive the car a lot, especially at speed, think about adding a PS oil cooler. Like my crew says, "You had to have a Hot Rod" ...it never ends. Upgrade this, have to change that... it's a sickness! Let us know how you make out. Thanks
I have been dragging my feet on reassembly just because I am in no rush as there is still snow on the ground and I want to make sure I have enough knowledge before I go after it.
The only thing I am not 100% on is after making the dummy bearings and checking the pattern you reassemble with the calculated shims and reinstall the pinion with the crush sleave, once preload is achieved do you remove the pinion nut then install the oil seal? This is how it seems in the videos I watched, doesn't removing the nut lose preload? Or is the object initially just getting the sleeve crushed and once it is done putting the seal on and retorqueing the nut is easy??
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
Ditto! Be aware. Crush sleeve is a bear to crush. Make sure pinion nut and washer are well lubed. Amount of bearing drag goes up quick once clearance is out of bearings. Check drag early and often!
Ratech has a new crush sleeve called a smart sleeve. I ordered one to make setting preload easier, it will crush at 150# Also made my calculation from centerline with my tool but the marking on the pinion gear says 279. is this 2.79, 3.279, 2.279? the math doesn't work as 0.279 ideas?
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
Surprised no one had an idea on the pinion marking? Still trying to make a calculation with it. With the bearings pressed on the carrier I am going to shim pinion today and try to do my first fitting. But with the marking just saying 279 that will not help me much with trying to make a calculation
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
So I did a preliminary fitting and with some trial and error I go these patterns and the hit the magic 7 for backlash.
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
So little high on ring gear means add a little pinion shim?
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
According to tool I bought and if the markings do mean 2.279 it is saying I would need .154 shim. Either math is wrong or I need a lot of shim. Is it possible to need that much. The photo I posted is with the stock shim. I have added up to .020 more shim and it still hasn't moved much more to the center.
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
ALso maybe I am a little confused on the centering. I understand center toe to heel, but is it suppose to be center as far as gear mesh depth. You can see how at top of gear compound is all wiped away, should it be missing the top edge of the gear and only making contact in the very middle? I have added up to .023 shim and toe to heel movement has been very minimal. But there has been no movement to make only middle contact with gear? I am thinking about just going crazy and adding the entire shim pack just to see how radical the pattern will move
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot
Something isn't right. I don't recall ever using anywhere near that much shim on a pinion gear. Does the gear manufacturer have a help line you can call to gain insight on the etched numbers? I use a depth mic and a bar I made up to measure from the split line to the pinion face. Is that something you can get ahold of in an effort to double check measurement?
I tried to call and use summit tech line but was on hold forever! I just went old school and just did trial and error. Because I was overthinking this and everyone was convinced this is hard to do I took it in and out about 12 times. Finally I landed on a really nice pattern, I put it back together yesterday and took it out for a ride.
Knowing I need a break in period before getting radical I just took it around the block to check operation. Guess what, couldn't here a single sound. Operates perfect. Just goes to show what you can learn here and from you tube videos.
My only comments for anyone else attempting, you got to have all the tools! I bought a press, I bought a yoke wrench, I bought a dial indicator for measuring back lash and I bought an inch pound gauge, Most items on amazon and really not that expensive, but without them this job wouldn't be for amateurs.
I don't want to get to far ahead of myself without further break in but for now, it works great!
Thanks All!
Restored by me. Not a professional. Restaurant worker by trade. YouTube forums and some trial and error built this beauty. Sheet metal replacement. Body work. Paint. Rear gears. Interior. And engine. ALL ME. Toot toot