UPDATE: What got hurt in the rear Diff or Trans?

I tackled some planned projects on the car for better drivability and performance (electronic fan upgrade, grade 8 bolts through the the driver side motor mount and a torque strap on passenger side, and heavier guage starter and ground wires to help with starting). And after some cruising to make sure all was working, I started having fun and hurt something.

I need your help to figure out what I hurt on the rear or rule it out so I can focus on the trans. Gave it near full throttle from a stand still. Took off nice and straight and hard. Then felt like it was in neutral and gave me a really bad metallic clattering sound. I let off the gas and as the rpm dropped the car lurched and started moving fwd again but with the horrible metal grinding sound. I was literally minutes away from home so I limped home. If I hit the gas too much it freewheeled again and then would buck and catch with that metallic grinding as the rpm dropped. Oneven time it locked up and the car tried to stop in its tracks then bucked and moved fwd again. So I idled on home the rest of way. My drive way is steep and it didn't do anything weird when I had to give it the gas to go up. I also didn't hear or feel the grinding or anything else while idling forward but its kind of hard to over the Flowmasters.

So what do I look for.

I figured I'd start with the basics. Disconnect driveshaft and check trans mount, u joints. Lift rear of car put in N and spin the tire to see if they go the same way like it should. Then I'll put one side at a time on the ground and try spin the opposite tire to test if the SG is still holding and how strong. I'll look for any obvious signs of damage, listen for anything wierd.

Anything else I should look for before I start talking about opening it up? What to look for when I do?

What can I do to inspect the trans besides drop the pan and inspect the fluid? I just want to have some idea of what to look forward to replacing? Trans rebuild, wouldn't be happy about it but ok. Rear end, harder to find in good condition for my 1 yr only rear. Maybe use it as a chance to upgrade to Dana 60 or 727.

If I think of anything else I will add another post with the info.

It was the car in my signature, 71 Satellite sedan, magnum based 408, 904 with low gear set and trans go TF2 shift kit, 8.75 rear with 3.23 suregrip with 7290 u joints

I haven't gotten under it yet but will Monday. Right now I need to step away to keep my sanity and tomorrow is family time so no wrenching. I want to have a plan before I crawl under it. If you need any info off of it let me know where to look and I'll post it.

The good news is the wife told me "baby just order what you need to fix it". Gotta love the Mrs.

Sounds like you may have destroyed the flex plate between the engine and torque convertor.

great woman there my man!!!

That would be awesome but I'm not gonna get me hopes up. Will keep the fingers crossed though.

Thanks for the input. I didn't think to check it.

You think it could be the converter? I don't know what symptoms of anew injured one are.

does the Mrs. have a sister?

No, just a little brother

If you were spinning the tires in first gear, playing on & off with the throttle you may have hurt the sprag (overrunning clutch) in the rear of the trans. But with the loud metallic grinding sounds you described I still say you tore up the flex plate. Only takes a couple minutes to check it. Make sure you take a light under the car with you and look up into the bell housing area. The bolts could still be in the convertor with the plate torn up between the crank and the smaller convertor bolts.

Jack it up and drop the drive shaft then you can isolate the rear from the trans. I'm going with the rear end, trans will have to come out either way.

Yes, it could also be the rear end. He may have ripped up the ring & pinion since he did say it tried to lock up one time.

I'm betting on the rear axle. I suspect missing teeth on a ring gear (or spider gears if its an open differential) and the broken chunks floating around in the housing caused the near lock up.

The sad part is that if you broke the rear axle under power, you probably hurt the overrunning clutch as well, and it will fail the next time your pushing the car a bit hard.

Sounds like you have a good wife, do whatever you need to do so she stays around, good and understanding ones are rare to come by. Gene

That's what I'm thinking too, ring and pinion. No experiences to go off of just a feeling I guess. Im still hoping for the best though. I want to say there was a rotating scraping sound too. I happened so quickly though and I had so many thoughts flying through my head I probably missed some details.

I was already planning on sending the trans back to the builder to have the governor adjusted since I went to a steeper gear and stronger motor. If I drain the fluid and the inspection and checks show the rear to be OK I can have him go through the trans again. Everything I've read says exactly what you did about the overrunning clutch too so I'd have it checked out just to be safe.

Well, I disassembled my first 8.75 and feel pretty confident saying that its not the rear. I rotates through all the splines for about 15-20 minutes looking for any signs of damage and didnt find any. My SG may need to be replaced, or rebuilt (I think I have the clutch type) because I could turn one tire while the other was on the ground. Thats what that means right? I checked the ring and pinion and no signs of damage. while the rear was still together, after disconnecting the driveshaft, I turned the pinion and everything rotated nice and smooth, and quiet. There was no damage at the flexplate and all the u-joints were perfect as well. So Im going to try and lube the bearings with fresh grease and slap it back together.

I think its all in the trans. I was worried about both. This trans was rebuilt with a low gear set, Transgo TF2 shift kit and stock high stall converter. Is there anything in particular that I should do to is this time to ensure it lives? I've contemplated going SB 727 which means I would need to order a new yoke for the trans end of my new driveshaft but thats no issue really. I'll probably start a different thread just on trans build suggestions. I think I'll also look at some of the performance trans builders too, especially if the price will be similar. Last build on it was $1200.

Anywho, heres the pics.














What is this little piece. I cannot figure out where it came from. looks like a brake line clip maybe. I cant figure out where it came from and I hate not putting stuff back together the way it was.

That looks like the adjuster lock for the axle bearings

Yep. Axle end play adjuster behind the brakes on the passenger side axle.

At least you didn't grenade both the diff and the trans.

That's a cone type SG, and the fact you can turn one wheel while the other is on the ground means it's either shot OR you blew out the side gear axle splines inside the SG.

How do the axle splines themselves look?

http://www.moparts.org/Tech/Archive/axle/12.html

1st question: I didnt remove the axles completely so that I could reinstall them without risking damage to the axle seals in the event that I didnt find any damage. So... if I plan on lubing the bearings I need to pull them all of the way out anyway right? If so, then I'll pull them and post pics.

2nd question: If I were to order a SG unit such as Eaton True Trac is it something that I can set up on my own with basic tools or do I need expensive tools that I would only use once for this install in order to get things like the backlash set properly?

3rd question: If the setup is something that I wont be able to do at home because of the tools required, are there companies that I can send my assembly to to have a SG installed, and 3rd member setup properly and all sent back to me for a simple install? Or would you use a 4x4 shop to set it up for you? They have to do stuff like this all they time right? I dont have any Mopar specific rear diff folks near me that I know of right now.

Are you saying you think the the splines on the axles are probably damaged, or that the side gear in the SG are damaged?

Sorry for so many questions guys, Im trying to learn here.

Pull the axles out and inspect the spline on the end....especially the last 3/4 inch. They may be stripped.

Ok, I'll be back with pics in a few minutes

Axle splines look good. I also have a pic of the bearings on each axle. What do you guys thing about the green bearings? Figure I might as well replace them. Once I take a closer look at the bearings tomorrow I'll decide whether to replace with the green/sealed bearings or just clean and repack these. If I go with the green bearings then that eliminates the need to set axle end play right? I also noticed that the driver side axle is looks to be just slightly shorter than the passenger side at a glance: I marked them so I know which goes where but that is a good thing for me to remember. Is that the case?

Passenger side:







Driver Side:

Disregard the Green bearing question. I did a search on the subject and read through many threads. Dont want to get into that argument here. I have developed my own thoughts after reading them and stick with my original assessment. Clean and use what I have unless they are damaged. And I'd feel comfortable running either a new set of tapered or the greens but would likely go with the greens.

Oh, and thanks for the axle end play adjustment link UCUDANT. Seems no more difficult than setting front wheel bearings up.

I'll just add a comment on sure grip replacement...

There have been problems with the worm gear type "True Trac" units for the 8.75. The basic design is great but they are made with excess clearances which make them rattly/noisy under light throttle or coasting. There are several posts on this. The clutch type "Power-Loc" is a better bet I think.

The clutch type was out of favor for a while as it had manufacturing issues as well but seems OK now. The basic design is also good and they are rebuild-able. I have one purchased ~14 years ago which has worked great.

There may be a shop near you that can set one up. Alternatives would be to send the whole unit to a specialist like Dr Diff or try to sell what you have and order a complete 3'rd member. Re-setting used gears is tricky and even done well the unit may make a little noise (mine does, very light whine coasting and light throttle).

can you feel, with your finger nail, anything at about the 3/4" area of spline engagement on the driver side axle ? it looks like something going on there to my old tired eyes. maybe side gear starting to act on the splines indicate gear maybe having issues ? just something to check.

I have a TruTrac in the Imperial and set it up myself. There is no noise or slop in the gears. I'm rather happy with it.

Moparx:
I can just barely feel something there. Its on both axles. I took that as just the result of 45 years of force on the splines as an engagement mark. There isn't anything else that I notice with the splines so they should be just fine right? Especially if I get a fresh SG installed

Ahy:
Thanks for the info on the True Trac units. I'll do a search here and try to read up. Are there any other recommended units that you know of? Unless I find a shop local I'd love to send it to Dr. Diff. His reputation here is outstanding and I've purchased a driveshaft assembly through him that Im very happy with. If he gets his hands on it and the gears need replaced too, I'd consider a step up to 3.55's.

and i have a tru trac in the front diff (d44) in my truck and it's tight and quiet.

Did you install/replace your SG into a used set of gears or did you assemble all new gears and SG at the same time? If you did put a new suregrip with used gears by replacing a worn SG did your spacers change for setting your backlash? Did you use one of the dial indicaators for setting your backlash or did you set it by feel. I would really like to try it myself but I dont want to set myself up for failure. I hear conflicting reports about being able to DIY or needing to send it out to a pro.

I just took a tru track out of a friends mustang that has about 15k street miles and less than 100 1/4 miles passes , I had to beat one axle out because the side gears are thrust into the center of the case and ate into raising a large burr , drivers side worse than the pass side.

I can't see your pics here at work but I imagine the cone type is what is making the noise.

Did you find a lot of metal in the oil? When the spiders seize to the cross shaft the cross shaft breaks it's locating dowel pin and spins inside the case eating the case up. No way to fix it , throw it in the scrap heap where it belongs.

There are only 2 choices for a sure grip if you want something that will live long, dana/spicer clutch type or a Detroit locker, if you can put with the noise.

You need a dial indicator and spanner wrenches for the side adjusters, and you need to measure your current backlash and reset it to that when you are done or the rear will more than likely make noise.

Do yourself a favor and have it done with new gears or buy another one and you can PRACTICE on the one you have if you really want to learn to do it yourself.

looking at the ends of the axles in your pic's it appears as though there may be some debris in the center ??? If it's metal

I reused the gears.
The pinion went in with the same shims. On the carrier, I set it with the best pattern I could but used gears will not show a perfect pattern like a new set. It requires a bit of interpretation.

If you're not equipped to set them at home it's likely best to have someone else handle it.

That crush sleeve was a real bear to start. I was afraid I was going to break the tools, pull my bench over, or pop the vise off the bench. It took a 4' black pipe and the willingness to sacrifice a good ratchet to the lifetime warranty gods before the sleeve began to collapse. Once it moved things got much easier.

JohnRR:
I didnt find a lot of metal in the oil. There were some really fine particles that I would consider normal. The first 2 of the following pics shows the only particles found that were bigger than those. They were in the little bit of remaining fluid that was in the bottom of the axle housing.





TJP:
I dont know what that piece was in the axle but it wasnt metal. It kind of disintegrated when rubbed between my fingers. There were some fine mettalic particles in that little axle center and 2 or 3 particles that were bigger but still small enough I wouldnt look twice at them. Was trying to thing of something to compare it to size wise but couldn't. EDIT: maybe a little smaller than the tip of a ballpoint pen.

Also, here are pic of where the axles insert into the carrier. I dont see any damaged splines here either. Its one pic of each side.

Judging by the lack of metal in the RE, might be time to drop the pan on the trans and see if it shows any chunks / debris

What did you do to this 904 before you stuck it behind a 408 ? I've seen 904's with converter drive hub sheared off behind smogger 318's ...

Hard to tell in the pictures, but there looks to be scratches on the sure grip in the area of the cross shaft? Make sure the cross shaft is not loose and hitting the pinion gear.

TJP:
Yeah, I agree. Im looking to have a plan in motion today for a SG install and 3rd member setup. Then on to the trans.

JohnRR:
All that was done was a rebuild with low gear set, Transgo TF2 shiftkit, stock highstall converter. Before that it had lived a life of leisure in front of a very mild LA360

This is a good tool for setting pinion depth if you need one.

http://www.summitracing.com/parts/rat-10007/overview/

If it is a 489 case may want to get a crush sleeve eliminator kit too.

Drop the trans pan, I think you'll find evidence of the limits of a basically stock 904 in it ...

I can see the pictures now, all looks sort of good except for that cone type of course. Since the wifegod gave you the ok lose that thing now. I know of a in Mi. that will buy it from you .

What a novel tool , have you used it ?

I'll second the solid spacer in place of the crush sleeve.

Hey, all. Thanks for all the input from everyone so far. I've learned a lot from this disassembly, inspection and the info you guys have been putting out. I've also used the google feature on the forum and read too many threads to count on a lot of the stuff mentioned here.

I havent touched the trans yet but here is the plan of attack for the rear diff. I spoke to Dr. Diff and he thinks I'll be fine to use the gears that I currently have and install a new SG. I just have to make sure the backlash is reset after the SG swap to match what it is now and check the contact pattern like normal. Im just trying to decide between the Spicer Power Lock and the Eaton True Trac, Im leaning Power Lock. Im going to have the local 4x4 shop do the setup for me. I stopped and talked them today and they are familiar with the mopar 3rd member and asked me about the crush sleeve, I just have to talk to the guy tomorrow who does the ring and pinion setup. Im also picking up the solid spacer to replace the crush sleeve. I've decided to go with a set of green bearings as well. I feel comfortable using them and think they will work just fine. If they dont, the process to re-install some factory style would be too easy, but I dont think that will be necessary. I like the plug and play aspect and I figure if they can go 100k miles in daily drivers they should be fine for me.

Once I get the 3rd member back and I re-install it and the axles then I'll either drop the car at the trans builder or I will have pulled the trigger on an ordered trans from performance builder. If I order one I'll pobably go 727 and a 727 Yoke to fit my 7290 u-joints. If I go with the local builder I'll have my 904 built.

Make sure to get the green bearings with the snap ring and separate retainer plates, not the ones where the retainer plates are part of the bearings.

This snap ring style:
http://www.doctordiff.com/green-bearings-pair.html

Not this style:
http://www.moserengineering.com/other-pa...-snap-ring.html

Definitely. Im going to order them through Dr Diff.

The tool works great! I have one for the 8-3/4" and Dana 60.
I also have the Proform Universal pinion setting tool, but I found the Ratech tool quicker and easier to use.

Here is the tool instructions:
http://www.ratechmfg.com/pinion%20setting%20tool.htm

The gauge measures off the pinion head to the bottom of the bearing bore, and the gauge has the correction number to use for the bearing center.

The universal tool takes more setup and calculations to do the same thing:
http://www.jegs.com/InstallationInstructions/700/778/778-66516.pdf

Thanks, I have the universal tool , I may buy both that ractech tool to use on the 8.8 I have to setup this weekend and get the 8 3/4 for one I need to do at a later date.

I wonder how accurate the measurement taken though is because the end of the dial caliper is not a round point like the end of a dial indicator is ?

Placed my order today with Dr Diff. Heres my parts list.

-powerlok suregrip
-solid spacer kit
-Green bearing kit (with retainers)
-Friction modifier
-reusable 3rd member gasket
-pinion seal

I will pick up some fluid in the viscosity he recommends when I do the install. I found a shop that can do the setup for me. Im going to see if he will let me watch as he does the setup. I've watched a lot of videos and done lots of reading but in person would be better I think.

Now on to the trans...

Bear in mind, when changing from a 904 to a 727 you'll have to shorten your driveshaft approximately 4" too.

did you get bearings for that power lock , they are not the same as the ones on the cone type and you don't really want to reuse them.

Considering you have a high mileage cone type it would be a good idea to change all the bearings after all the metal that has been circulated thru them over the years.

Jwilli500:
I didnt think about that. Thanks for the reminder.

JohnRR:
I did not get the bearings. I'll give him a call and add that to the order.

Anything else that I may have forgotten?

roe

Looks like you got everything, just make sure to tell the shop do it to set the backlash to the same spec as it is before he takes it apart.

Some people like to tighten the backalsh up because it will grow or the factory set it to the top of the spec , it'll make noise if it's not back where it was.

Roe if your pinion pre-load still feels good and the seal isn't leaking there is really no reason to pull it apart. I have just changed the carrier on dozens of 8 3/4 rears without pulling the pinion gear out. Now if it wasn't smooth turning or the pre-load was too loose then pull the pinion out and inspect the bearings.

Oh you might want to add a new pinion nut to the list if you are having the seal and spacer installed.

Gus

I'll have to post a picture of the inner pinion race that came out of the rear that had that true track in , no more than 15k miles , it'll give you an idea what cone type bearing races look like after many thousands of miles ...

He has to pull the pinion out of the housing to put the solid spacer in, sorry but it would be stupid to not put fresh bearings in it .

^^ This. Why go through all that with new parts and such and NOT put new bearings? I mean.. you're in there already soooo...

Did you guys happen to see new pinion bearings on his parts list??? It looks like he's going to re-use them

Gus

I didn't order any but I still can if you guys think I should. I figured if axle bearings can be cleaned, repacked and reinstalled why not pinion bearings? Without opening it up up they show no signs of issues. Pinion rotates nice and smooth and quiet. But like I said, if it's best I can order some of those as well.

Problem is, if there was any debris that ran thru the bearings you've brinelled them and the end is coming. I don't think you found any chunks, but it won't get easier or cheaper to replace them than right now.

It makes sense. I'Lloyd order some up tomorrow

It's a cone type, it generates small chips BY DESIGN every time you make a turn. There are no magnets to collect the chips so they circulate in the oil and get forced in between all metal to metal surfaces that have the film of oil between them .. BEARINGS AND GEARS ...

Good choice , it would be stupid not to replace them , the rear has to be completely disassembled to install the solid spacer.