Couple things come to mind. Did you remember to refill with diff fluid? Hard question to ask but it's not like it's never been done before. If you did remember to refill it, did you use the correct fluid required by the "posi unit". I realize you lost the instructions for your posi unit, but I am sure they can be found on the internet. The reason I ask is this, I changed the fluid in a 9", drove several miles to a local cruise-in, and while making turns in the parking lot, I heard a LOT of painful (to me) and expensive sounding clunks, clangs and bangs from the rear end when turning. Turns out I needed to use a friction modifier additive with the posi in that rear end and I had failed to add some. Got home, added the "posi lube" fluid, problem solved. That being said, I think I'd be taking a really close look at the axle lengths on both sides ... including the one you just changed. I have personally learned that doing something twice does not always mean the second time was done correctly. My only other thought at this time is ... was something damaged internally due to using too short of an axle? Hope you get this figured out soon.
Yes to oil and additive. All topped up. I got the rear back out and the diff on the bench. I can't see or hear any issues when looking and rotating the ***embly by hand. With the noise it's making I was sure I'd see or at least FEEL something in there. I can see a slight wear pattern on the gears already and they look good. It's all clean inside. Backlash is good. I haven't put an indicator on it but by my machinist's feel, it seems around .010-ish. I haven't taken it apart to check spiders, I really didn't want to have to do that...But I may have to. I can see them through the hole in the carrier and there's nothing obvious. I don't see any sign of axle being too long or short. I sounds like a rattly-thunk. Like the pinion is rattling around, but it's snug (all new) and the video shows it spinning nice and smooth. I tried to load a video but I can't get it to take it right now. I did videos of each wheel spinning in 3rd gear with jack stands under the rear axle so all weight is on the suspension, and more of the front U-joint at the trans and at the rear. I can't see any vibrations or anything flailing about. Everything spins smooth and steady. All the exhaust pipes are clear and not hitting anything. I can feel it in the shifter when it thunks. I even took the drive shaft out and ran it that way to isolate the trans and rear. It was quiet and smooth. I thought maybe a U-joint but they both seem tight (both new). With it all hooked up, I pulled and twisted everything to find any play and got nuthin. Maybe I'll take the chunk to someone and have them go through it all. Driving me crazy.
This kind of stuff on a new total build is enough to make us crazzy. Being you have had it apart several times no doubt you now what you're doing. No doubt it's going to be something unusual. Maybe just keep driving it till it gets obvious to the sound or eye. I wouldn't think it's something that will cause a disaster, but I'd keep my Triple A card with me. Who knows, maybe it will get less and less till it goes away.
LOL! That's never worked for me before... Would a bent or warped housing cause issues like this? Still trying to get the video to load.
Sorry to harp on this but I can't help shake the feeling that your issue has to do with axle length. I am more than a little confused as I think (I could be wrong) you first mentioned that the original axles wouldn't work with the new center section which seems odd to me ... ***uming the rear end is factory stock width with factory Ford axles. To put this possible cause (wrong length axles) to bed, I would contact the manufacturer of the center section/posi unit and ask for specifics regarding how far in on each side, the axles need to be in order for their product to work correctly. Maybe your newest axle, after possibly losing 3/8" to that spacer (if the spacer actually affects axle length), is just barely catching the second set of splines and what you are hearing is it grabbing/almost popping out. Since you are running 28 spline axles (very common factory 9" spline count), is it possible to locate any random 9" "chunk" and just toss it in ... no posi, any random gear ratio, just to get the car running and driving. That would certainly tell you whether the new center section is the issue and would get you on the road too. "I don't see any sign of axle being too long or too short" leaves me wondering exactly how the long both axles need to be (for the center section you are using) and, exactly how long your axles are compared to the required/expected length. Keep in mind, I am only making ***umptions on possible issues based on information given that I may be interpreting incorrectly Edit: Basically this ... find out EXACTLY what axle lengths are required, only then will I allow you to rule it out as a possible cause
At this stage; if you haven't already tried it; maybe put the axles in the housing without the drop-out and check if the ends come out in the right spot?
Is your drive shaft too long and bottoming out in the transmission. With it at ride height you should have about 1" of movement of the yolk into the trans case before it bottoms out.
With a bent housing, new axle bearings and fresh new center section you should have a noticeable issue installing the bearing into the housing receiver. If they are a snug fit and you can install them both to the seat point by hand you have nothing to worry about. Now if you're getting your leather headed mall to bump them in, you could have a housing issue. I ***ume you had this housing narrowed to work with the Ch***is. I have seen guys try to freehand them at home. That generally has Bad results. I have seen home builders take good housings and damage them welding on necessary brackets. A mandrel is the only way to check or hold straight a housing when welding anything on them. When doing ANY custom axle length homework this tool is a MUST HAVE!!! It ends all the "I think it's right" Bull ****. You can't miss with having the right tools. Even with an unmodified housing I use this tool when ordering custom axles. You can't go wrong that way. Yes, you can buy them from Dutchman and several others in the Axle business.
OK I ordered one of those dog bone gages. Should be here by Thursday. Surprisingly cheap for the value it will provide. In the meantime I'm going to check the straightness of the axle housing. I welded on brackets, etc some 30 years ago and I've learned a lot since then. So, whether I warped it or not, I'll find out. I'm thinking I did, or it was already warped a bit. This whole unit came out of a 1967 Mustang GT 390 of unknown history. Small bearing, non-tapered, stock length housing. Custom driveshaft with about an inch and a half of travel. The axles DID require some persuasion to install. One more than the other, which SHOULD have given me a clue. One of the original Ford axles was bent. I had put them in my lathe to "clean" them up when I discovered that. So I decided to replace both and use a 4 3/4" bolt pattern. Now to find someone local that can straighten the housing. I need this done ASAP as the Rodders Reunion is just a little over 4 weeks away. I thought I was done but low and behold, I'm down to the wire once again. I appreciate all the comments and suggestions.
To check true center line requires a center section with a register for the Mandril true to carrier bearing center line and out to both axle bearing housing center line. Thos 4 points need to be as true to each other as a Rifle barrel bore. To straighten one also requires the same tools.
Yes and I have the word out for someone around here that can do all of that. This is beyond my tool box. Those tools ain't cheap enough for a "one-time" use. I'm not likely to ever do this again at my age so I'd rather pay someone to do it that already has the tools...and experience. I put the axles in (no center section) and bolted down the retainers. Put wheels on and set it on the floor. Rotating the housing (wheels chocked front and back) about 1/2 a turn, the wheels "toe" in and out a good 1/2 inch. Don't need a measuring device to see it. Yeah, it will need straightened. I think I need to start there.
That sounds like a great "quick and dirty" way to check if the axle housing is true. You keep approaching the job this way and you'll get it figured out.
You push the drive shaft in until it bottoms out in the transmission, then pull it out 1". That is where it should run when driving the car. I was giving an example of how to check it.
A former neighbor bought a used 9" with the intention of having it shortened to fit his '63 Ford Falcon while also getting Strange axles installed. He located a random 9" through the local buy/sell and took it to a very reputable local ch***is shop that is owned/operated by the same guy for the last probably 50 years. The shop owner not only builds cars, he races too and was inducted into the Canadian Drag Racing Hall of Fame. That being said, when my neighbor picked up the rear end after having it shortened, I was extremely surprised (shocked actually) to see that the housing ends were not in-line with the axle tubes. Apparently the housing itself was bent so, rather than straighten the tubes before welding on the ends, the ch***is shop dude decided to simply line up the housing ends to the center section using the correct jig, then welded the lined-up ends to the "noticeably bent" axle tubes. It looked weird. Now, the housing ends don't know the difference and neither does the housing, axles or bearings but it looked ... really lame. My understanding is that the "correct way" to do the deed would have been to straighten the housing first, using a torch (heat-cool) or possibly a press THEN weld the ends on but that's not what was done and this was from someone who has been in the business for half a century. My point being ... if you are taking your housing in to be straightened, it might be in your best interest to fully understand how they plan to straighten it. Although the "chop off the ends and weld'em back on straight" does and did work ... it looked really ****py. I get that your housing doesn't need to be shortened so the ends can stay put but, that might not stop someone from chopping off your ends and welding on new ones (or your old ones), without bothering to straighten the tubes themselves. My understanding is, there shouldn't be an issue simply straightening your existing housing ... if that's what you want, make sure they know it and you understand what it is they are intending to do to solve your issue.
I’m not sure where the bent axle housing rabbit hole began, or what that has to do with a clunk. I do know if you didn’t use limited slip additive that thing can make some nasty sounds especially when turning. I have a jig for a 9 inch that consists of a trued shaft and pucks that fit the housing. You are welcome to use them if we can figure how to get them to you.
I don't remember if we touched on this or not but the additive needs to be mixed in before it actually can do its job. For me it's up on jackstands, put it in gear and let it run a while before I ever do the test drive. Up and down the driveway or even just around the block really doesn't do the job. I know it sounds weird but works for me.
Post 163 and post 166 mentions the bent or possibly bent housing. Although a bent housing may not be causing the clunk, I do agree that now is the time to address how true the housing is (if it is suspect) and straightening it if indeed it is warped.
Keep in mind not all 9" housings are created equal. Any truck housing is a stout piece and early ones (up to about '64) are fairly stout, but differences started showing in '65. Ford went to coils on the rear suspension on the full-size and those were stronger and equal to the truck housings. Any coil-equipped housing will be the best choice if using a car housing in terms of strength. The downside is if using on a leaf-spring car, modifying one introduces welding and opens the door for warping. When Ford started installing the FE in the intermediates in '66 and the Mustang in '67, these were lighter-duty compared to the other housings. In '69 and with the arrival of the 351, an even lighter duty 9" version appeared. I can tell you from personal experience that any suspension points inboard of the ends more than about 8-10" that can present a load can bend the housing. On the rare occasions when Ford offered an optional rear sway bar on a car with leaf springs in this era, the bar was mounted to the body/frame and had links down to the axle very close to the spring pads to prevent this bending. This needs to be taken into consideration if using something other than leaf springs in the OEM position. The housing may need additional bracing to prevent this. And how much housing bend is too much? Ideally, the axle should easily push in if the housing is dead straight. But in reality, that's fairly rare on used housings. 2 or 3 light taps is fine, 3 or 4 moderate hits to fully seat the bearing once its in more than halfway is also acceptable in my experience. These are why they make slide-hammer axle pullers. But if you have to get heavy-handed to remove or fully seat it, it should probably be addressed unless you don't mind replacing axle bearings (and maybe axles) at every oil change. There is a hillbilly fix... While I don't particularly recommend this, it can work with no ill effects although it precludes easy bearing replacements. Pull the axle, and set up a hose with cooling water onto the bearing. Then take your angle grinder with an 80-100 grit sanding disc and taper the outer diameter of the bearing race in towards the center. The water will prevent overheating the seals or grease in the bearing. Start at the 'inside' of the bearing, moving towards the wheel flange. You can usually leave the last 1/4 of the bearing width as-is. Remove about .025" (.050" total), if more is needed your housing is really bent and you may have misalignment with your brakes. You may not need that much, you may want to test fit it a few times.
When I was an open shop, I got paid by the hour. Doing the back yard repair was only for Friends that wanted to help with their repairs, but they do work.
I took the housing to a local-ish (an hour drive) guy that a hotrodder friend suggested. The guy I took it to builds hot rods and drag cars so I hoping he will fix it right. He did say he would cut off the bearing ends and reweld them back on straight using his fixture. I also wondered how that is going to look, but if it works and just looks bad...I have bondo and I ain't afraid to use it. LOL I did use friction modifier from the same place I got the diff from (Yukon) so it's the (stinky) stuff they recommend for their stuff. I put a quart of (recommended) oil into the axle and part of another quart. I then put the F/M in that bottle and shook it up. Then finished filling to the fill hole. I know it's not all fully mixed but I figured it would finish mixing as I drove it...when I actually GET to drive it... I ain't even driven this thing enough to tell if the freakin' brakes work or not! That's not entirely true. Going down the hill to my shop they worked. I had to step hard as I'm used to power brakes and this car doesn't have a booster. One headache at a time...
I got the housing back today. He was quick! Looks fine. Not perfect-looking, but at least it's straight. It was bad off center. He said he has seen worse. May do some bondo on it. May just paint it black and let it go. It's not a show car, it's a hotrod. I'm now waiting on my axle seals and gaskets to get here. In the meantime, I'll prep and paint the housing again.
Why can't things be simple? I measured the original Ford axles and the new ones from the inside surface of the bearing where it bottoms out against the bearing bore, to the end of the axle shaft and got 1/32" difference between old and new. That's .031", half of 1/16. When I put the new ones in the housing (bottomed out) with the cut template it's a huge difference. About 1/4 on the driver's (short) side and nearly 3/8" on the long side. Does the Tru-trac diff made that much difference? Or is this template wrong? Or am I doing something else wrong?
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