Rearend Blues! (kinda long)

[90'5.0 Conv]

Ok, I'm beyond the point of being frustrated! I don't know what else to do.

For anyone that doesn't know, I bought a set of Ford Racing 4.10 gears to replace my existing 2.73's. I've used all new bearings and all the original shims. I asked before if the original shims would work with the Ford Racing gears and everyone that responded to my post said they would so thats what I used.

Here's what I've done so far: I have everything put together, the ring rear assembled to the T-Lok, the pinion bearing pressed on the pinon (all original shims). First, I put the pinion in with the crush sleeve, bearing, oil slinger and new seal. I torqued it till there was no play then turned it about an 1/8th turn. Everything seemed good and turned fine. Then I went ahead and put the ring gear T-Lok assembly in the housing. It was a real tight fit with the original shims. (Not sure how tight it should have been) I did manage to get it in and everything looked good. I spun the ring gear and it moved very smooth.

From there, I went ahead and put the main caps on. After I torqued them down, the ring gear and pinon were seized up against each other. The ring gear is not rubbing on the housing or anything. I loosened the cap bolts up and proceded to bang the ring gear assy back out.

I came on here and asked what should I do and more people thought that I needed to get a new crush sleeve and try again so I did that. I torqued just till there was no play side to side and left it at that, put the ring gear assy back in and the same thing. Pinion and ring gear froze up on each other. I don't know what else to do.

Everyone seemed to think the original shims would work. Are they supossed to or not? Should the pinon gear be so hard to get out after the nuts backed off of it? I beat on that thing for eternity trying to get it out. Should the ring gear fit really tight? Please give me any advice or experiences that sound similar to my problem. I really appreciate the replies.

Thanks Everyone

James

[89 ATI]

I told you in your last post that your pinion is fine it is your ring gear that needs moved. You have too much shim between the housing and the bearing on your carrier. You need to put a thinner shim between the bearing and housing to move the ring gear away from the pinion gear. You should have .006 and .012 of an inch play between your ring and pinion with the caps torqued down.

[90'5.0 Conv]

Sorry, wasn't trying to ignore you. Its just that I had been told that you were able to use the original shims and really wanted to believe it. How do I know how much to take out? The use of the original shims is not true then or is that just in some cases? The shims that are in there now are stock and huge. Does anyone know the sizes?

Thanks, James

[89 ATI]

I used the stock ones in mine but I have 3.55's. It is one of those things where you need to buy a shim kit and keep trying different thicknesses until you hit the right combination. What ever you take out from one side you need to add to the other side so you can keep the preload on the bearings right. I would first try swapping the stock shims to see if you might get lucky.

[Jeff Chambers]

To measure the backlash, you need a dial indicator set up so that its tangent to the teeth of the ring gear. Adjust backlash by removing/adding shims to move the ring gear into the pinion (reduce backlash) or move the ring gear away from the pinion (increase backlash). You'll also need a micrometer so that you can measure the shim thickness so that you know where you're going. For example;

Left Shim/Right Shim/Backlash

.281/.245/0.000 (initially tight)
.276/.251/.005
.273/.254/.008 final

Actually since the gears are a hypoid shape a .003 change in shim won't net exactly a .003 change in backlash, but it will be close. The Helm manual has a table that provides the shim change needed to obtain a given backlash change. Don't forget that the main caps HAVE to go back on the same side that they came off and must have the arrows pointing outwards. With proper carrier bearing preload, the carrier should be hard to remove (i.e. gently pry it out). Too little preload and the carrier will move under load, too much and you'll fry the bearings pretty quick.

From the way it sounds, you probably don't have enough preload now on your pinion since you just snugged it up (was probably closer to correct the first time). You may be able to get things assembled without the proper pinion preload, but you'll probably wind up with premature bearing or gear failure. Without the proper preload, the pinion will move excessively under high load (launch/acceleration). The pinion will get sucked deeper into the mesh and end up moving side to side wearing out the bearings and possibly the gears. Better go back and preload it properly. Since you'll be crushing the sleeve further, you don't need to change the one you've got in there.

Check out my website for some detailed instructions on gear setup. I worked in the engineering lab at DANA's Spicer Axle Division during college and have probably setup up more than a hundred gearsets in everything from Jeeps to UPS trucks. I just swapped to 4.56's in my Mustang last week and did a 3.73 install in a kid's mustang over the weekend.

[90'5.0 Conv]

Ok, I don't know what else to try. I went ahead and retorqued the pinon nut back like I had it before. All the way until there was no play, then about an 1/8th turn. I put the ring gear in and shimmed it over to the left just a little. Then, I torque down the caps just a little bit and the darn thing locks up so I shim it over again and torque the caps just a bit and no matter what it locks up. I kept moving over till I hit about 4 shims(all small), and nothing. If i leave it loose, it seems to move fine but as soon as a tighten the caps, especially all the way to specs, it will lock up. I even checked the wear pattern when it was moving and it had a heel pattern on one section and a toe pattern on another and a good looking pattern somewhere else. What gives? I'm about ready to call it quits. Anyone know what could be going on here?

Thanks for your replies, James

[Jeff Chambers]

Something isn't right, that's for sure. Are you sure that you're getting the bearing cups in straight? Sometimes it can be a pain to get them in straight and get the shims in. If you changed carrier bearings, then the total stackup thicknesses of the shims may need changed just based on the manufacturing tolerances of the bearings, but it shouldn't be that much.

The only other thing that comes to mind is ring gear run out. If the ring gear is warped, or if you bent the ring gear mounting flange on the diff, it might cause some of the problem you describe. Mount the diff so that it will rotate then set a dial indicator up on the back face of the ring gear (perpendicular to the back face of the ring gear). Rotate the ring gear through a full revolution and note the total indicated runout. Eg. if the indicator goes from +.012 to -.005 then you have 0.017" of TIR. The maximum ring gear runout should only be 0.003" to 0.005" max. Anything more and it'll cause uneven wear. Is the ring gear completely seated on the mounting flange? Run a 0.002" feeler gauge between the ring gear and mounting flange all the way around. You shouldn't be able to actually get the feeler gauge to slip between the RG and mounting flange.

[90'5.0 Conv]

Jeff:Thanks for your help. Yes, I did replace the carrier bearings and I do have the races lined up straight as far as I can tell. I kinda got frustrated with it all today so I'll check the ring gear runout tomorrow and I'll stick the feeler gage in between the ring gear and T-lok assy also. Thanks for your help. I really appreciate it. There is no one here (where I live) that can help me and this is the first rearend I've ever done so you've been a great help as well as everyone else thats replied. Everyone should be learning alot that reads this. I know I am.

Thanks again, James

[Jeff Chambers]

Maybe you ought to check the part numbers on the carrier cones and cups while you're in there. Maybe you've got the wrong cups and you're actually collapsing them under torquing and causing the bind. I only say this because the Ratech kit the kid purchased last weekend for the install I did came with the wrong carrier cups (the cones were correct). Turned out they were the cups for a Cheby rear and were too large an OD. Ended up reusing his old cups with new cones...not ideal but the option he chose.

[90'5.0 Conv]

Well, Finally after what seems like years I've got it in. Turns out the guy that supposedly put the stock shims back on the pinon before he pressed the bearing on didn't. That was problem my first problem. The other thing I ran into was the stock shims didn't work even after fixing the pinion shims so I had to shim it over to the right 3 small shims with my stock shim on that side. The left was much smaller than stock was. I'm tested backlash and it was .013 which was about as tight as I could get it with the shims I had. Ring gear runout was fine and the wear pattern was perfect. I guess the only reason the ring gear had the funky wear pattern before all that was obviously from the grinding type action I was getting from the pinion being too far from the ring gear. I just got back from my test drive and everything seems pretty different. The shift kit is really put into action now, even though I haven't go on it yet. There is a whine about 35-40mph I'm guessing since my speedo is off now. LOL Othere than that, I can't wait to go to the track tomorrow night and post my new times on here. I haven't got on it yet but I sure want to! A big thanks to everyone who replied especially jeff for sticking it out with me! Thanks a million. I'll keep ya posted.

Thanks, James

[schizcat]

ok, so this post was a little old but i am having almost the same problem. I can turn the axles to the rear without any probs. just cant turn them forward. there is some play in the pinion and i have a feeling this has something to do with it. the pinion seems to "slide" backward when trying to go foward. and will slide back forward when the axles are turned backward. anybody ever seen this? i may have not tightend the pinion nut in all the way seeing how im using an old air gun. i do have access to a new air gun and can use that if anyone thinks it will help. i did have the ring and pinion installed by a shop

[Jeff Chambers]

Pinion will be sucked into the meshed on the drive side and pushed out of the mesh on the coast side. This is due to the hypoid shape of the gears. If you can see the pinion moving fore and aft, you've got problems. The pinion nut should be torqued until there is approximately 18 to 24 in-oz running torque on new bearings or 10-15 in-oz on used bearings. The pinion will not move fore/aft if the bearings are properly preloaded. Basically, the pinion has opposed angular roller bearings that are preloaded against each other via the crush sleeve/pinion nut stack up. For a 8.8", this is about 0.008" of total bearing preload, or 0.008" past zero lash. This is the pinion zero lash point, not the zero last point of a new, unused crush sleeve. The bearing have to be properly preloaded to carry the axial loads from the hypoid gear mesh properly.

You shouldn't use an air gun to preload the bearings...the control just isn't there. It'll take less than 1/4 turn (on average) to get to proper preload after reaching the zero lash point. You need to be using a breaker bar and sneaking up on the preload about a 1/16th turn at a time. Too much preload and you'll burn bearings, too little and you'll ruin the gears.