How hard to install an OBX in 520/555 trans?

[Clay]

Well, thats the question. I have a 520/555 hybrid.

Ive never messed with diffs much, at least never set any preloads, or gear lash, though I think I have an idea of how.

So how hard is it to install?

[TurboGLH]

Since you've already got a hybrid it's a fairly simple task.

Do your OBX prep first, you'll find that the washers are crap and that the threads need to be chased on both the carrier and the bolts. You'll also find that with the bearings installed the axles no longer fit well so install the bearings and then clearance the axle opening until fitment is back to normal.

Pull the diff cover and both bearing retainers. Remove the races from both the steel and alum retainers, be careful not to lose the current shim in the steel housing.

Install new races and current shim into retainers and bolt the obx and both retainers (but no diff cover) into the tranny. Only two bolts are necessary on each retainer.

Now use a magnetic base dial indicator to see how much play you currently have. It will probably be in the .050 range. Check 5,6...10 times. Check, check, check and recheck. Once your certain, add an additional .008 on top of that and order a new shim from the dealer. You can order one size up and one down if you feel more comfortable, just in case.

Leaving the obx and the aluminum retainer installed. Remove the steel retainer and then the race from the retainer, install BOTH the old shim and the new shim from the dealer.

Now, if you have a set of feeler gauges, place the steel retainer back on the tranny, but don't bolt it down. Use the feelers to verify that you have some clearance between the backside of the retainer and the case, the amount of space you have should be equal to you preload. It's not an exact science, but if you have .001, or .015 or even none, you can be fairly certain you have the shims in wrong of the wrong sizes. That's why you check and recheck.

Provided you've found your preload to be A-OK, Remove the obx from the tranny, remove ring gear from the current diff and install on the obx.

Reinstall and you done.

[jeff1234]

Chris, I have a couple of questions

Pull the diff cover and both bearing retainers. Remove the races from both the steel and alum retainers, be careful not to lose the current shim in the steel housing.
Do you suggest just replacing the race, or the entire bearing assembly. Is there a common tool that you use to remove the races? There is a disk with a hole in it in each retainer that would be easy to damage. Is this the shim or an oil barrier of some kind? My trans is a A523 that I am going to use OMNI driver side axles in, will these axles fit through the hole in the previously mentioned disk?

Now use a magnetic base dial indicator to see how much play you currently have. It will probably be in the .050 range. Check 5,6...10 times. Check, check, check and recheck. Once your certain, add an additional .008 on top of that and order a new shim from the dealer. You can order one size up and one down if you feel more comfortable, just in case

When you speak of play, are you referring to how much you can move the OBX left to right and back again?

Now, if you have a set of feeler gauges, place the steel retainer back on the tranny, but don't bolt it down. Use the feelers to verify that you have some clearance between the backside of the retainer and the case, the amount of space you have should be equal to you preload. It's not an exact science, but if you have .001, or .015 or even none, you can be fairly certain you have the shims in wrong of the wrong sizes. That's why you check and recheck.

If I understand what you are saying here, you seem to be saying that with the OBX seated against the race in the aluminum retainer, and the steel retainer seated against the bearing on the left side of the OBX, there should be clearance between the inner face of the steel bearing retainer and the mating surface on the case that equals the amount of shims installed. If this is the case, and supposing all the parts are friendly with each other, what amount of lost motion will show up between the ring gear and its mate? .004 .005, more, less???

Thanks for your help, jeff1234

[TurboGLH]

Chris, I have a couple of questions

Pull the diff cover and both bearing retainers. Remove the races from both the steel and alum retainers, be careful not to lose the current shim in the steel housing.

Do you suggest just replacing the race, or the entire bearing assembly. Is there a common tool that you use to remove the races? There is a disk with a hole in it in each retainer that would be easy to damage. Is this the shim or an oil barrier of some kind? My trans is a A523 that I am going to use OMNI driver side axles in, will these axles fit through the hole in the previously mentioned disk?

Absolutely replace both the bearing and the race. A lot of the time just trying to pull the bearing off will rip the cage off and leave you with just the inner shell.

The "disc's" are oil slingers designed to keep most of the oil away from the axle seals. They are very easily damaged if your not careful, the correct tool pulls them out and doesn't touch the slingers at all. If you don't have access to the race puller try a local tranny shop to see if they will pull them for you.

The TBI axles will fit correctly, the shaft size is the same on all the axles. It's the splines that are different, so the slinger will be the same for all years.

Now use a magnetic base dial indicator to see how much play you currently have. It will probably be in the .050 range. Check 5,6...10 times. Check, check, check and recheck. Once your certain, add an additional .008 on top of that and order a new shim from the dealer. You can order one size up and one down if you feel more comfortable, just in case

When you speak of play, are you referring to how much you can move the OBX left to right and back again?

Put the obx minus ring gear into the case and install the aluminum extension housing (I'll abbreviate AEH and SEH to save myself time here) with two bolts and then tip the case up so that it's bell housing down with the AEH hanging off the edge of the bench. Now, leave the oil slinger out, but install the new race and your old shim (which will come out with the race, it may be stuck to the back so be careful not to throw it out). Bolt the SEH onto the tranny with two bolts. Now place the dial indicator base onto the SEH and adjust it so that when you LIFT the obx the indicator changes. This will show you how much free play there is. Do this a minimum of three times, but as many as it takes for you to be comfortable with the reading. This is the amount of free play you have, now add the .008 on top of that amount and you know what size shim you need to order to set the proper preload.

When you get the new shim, you'll need to pull the race and shim back out, install both the old and the new shim and the race back in and proceed to the step below.

Now, if you have a set of feeler gauges, place the steel retainer back on the tranny, but don't bolt it down. Use the feelers to verify that you have some clearance between the backside of the retainer and the case, the amount of space you have should be equal to you preload. It's not an exact science, but if you have .001, or .015 or even none, you can be fairly certain you have the shims in wrong of the wrong sizes. That's why you check and recheck.

If I understand what you are saying here, you seem to be saying that with the OBX seated against the race in the aluminum retainer, and the steel retainer seated against the bearing on the left side of the OBX, there should be clearance between the inner face of the steel bearing retainer and the mating surface on the case that equals the amount of shims installed. If this is the case, and supposing all the parts are friendly with each other, what amount of lost motion will show up between the ring gear and its mate? .004 .005, more, less???

Correct, with the SEH unbolted, you use the feeler gauges to verify that there is indeed a small amount of "extra" shim that will be the preload. It should be the .008 that you added, but it can be as low as .006 or as high as .010.

I'm not real clear on what your asking in the second half. There is no backlash or any adjustment to set mesh between the ring gear and the mainshaft. It's established by the machining of the case and the housings and is not adjustable.

[jeff1234]

Chris, Thanks for the help. Knowing that I need to seek professional help on bearing race removal saved me from attempting to get those parts off myself and generally fouling things up. I have the tendency to believe there is a way to do these things by myself. Fortunately I also have a tendency to ask for assistance and then take the advice.
Your answer concerning the ring gear clearance confirmed what I thought might be the case. As I looked at the trans, it seemed likely the tooth engagement was a machined in tolerance, but I wanted to avoid destroying the trans because I didn't pay attention to every detail.
Thanks again for taking the time to address these questions properly!
jeff1234

[Clay]

Yes, a definate big thanks to chris!! He has basically outlined the complete installation of an OBX, and provided needed info to anyone who needs/wants it, and for free! I still dont know if Im brave enough to attempt this install myself, but if I do, Ive got all the info on how right in front of me. Thanks Chris!

[BadAssPerformance]

Yeah, Chris is good like that we got all this in a FAQ?

[TurboGLH]

Thanks for the kind words, I try to help out as much as I can.

As far as an an FAQ, not yet. But I'll be sure to write one up and get it up in the knowledge center asap.

[jeff1234]

Clay, I think you can do it. I already had the bearing retainers and ring gear cover off of my A523 before I asked Chris my questions and its pretty striaght forward. I am using a FSM that I bought at a swap meet in Jefferson Wisconsin. Its for "91" model year front wheel drive Chrysler cars and has a assembly/disassembly pictorial in the transmission section that is absolutely invaluable. I would venture a guess that if you tried to do this work without the manual, at the very least you would improperly seal the trans against oil leaks. So thats my recommendation to you, pick one up, or use one if you have one, you will be glad you did.
Chris is awesome to help us out with this info and not charge for it. Thats says alot about him and all the other guys and gals on this forum who share the experience and info about owning these little hot rods. If you went to the dealership right now, I suspect that it would be difficult to find many technicians who would have retained this knowledge much less have the time or inclination to share it.
So we are lucky people, type a question, push submit reply and before long someone assists you. Turbo-Dodgers, what great people!!

jeff1234

[TurboGLH]

I took the original post, mixed it up with some of the info from my reply to Jeff's questions, and outright stole a couple of sentences from Jeff's questions and rolled this up into an article in the knowledge center.

Everyone please take a look and double check for me, any typo's, error's of any kind, wrong info...please let me know so that I can get it fixed. Also, any suggestions are helpful also, if you think it would be easier to read in a different format.

http://www.turbo-mopar.com/forums/vb...e&articleid=63

[jeff1234]

Chris, I thought it looked great. It was much better than the original posts in my estimation, but we have covered the info alot at this point and so my understanding of the subject was complete. Hopefully others will read and chime in if they feel its needed.
I have one more question for you. The FSM says always replace the ring gear bolts. Is this really necessary or is it C.Y.A. to protect Dodge dealerships against liability problems. My trans was in a EFI car and only has 88000 miles. With the number of bolts in the ring gear it seems to me it would take big power to shear off the bolts. Perhaps there is a good reason they suggest this. Can you illuminate?
Thanks, jeff

[TurboGLH]

Chris, I thought it looked great. It was much better than the original posts in my estimation, but we have covered the info alot at this point and so my understanding of the subject was complete. Hopefully others will read and chime in if they feel its needed.
I have one more question for you. The FSM says always replace the ring gear bolts. Is this really necessary or is it C.Y.A. to protect Dodge dealerships against liability problems. My trans was in a EFI car and only has 88000 miles. With the number of bolts in the ring gear it seems to me it would take big power to shear off the bolts. Perhaps there is a good reason they suggest this. Can you illuminate?
Thanks, jeff

Yes the FSM says to replace them. No, I don't replace them on my personal transmissions and I've never had a failure. The reason we're supposed to change them every time is because they can stretch, but I've never found it to be an issue and I skip it when I put together a tranny for myself.

Thanks for looking, I went back over it again today and made some more changes, typo's, repeats, structure changes....just little things. It needs pictures, but for now it will have to suffice.

[TurboGLH]

Just an FYI to everyone. If you're in the market for an FSM, my personal favorite is the 90'. Because of the l-bodies still being in production it covers both the 525 and the 523/568.

Since the internal setup is the same between a 525 and the 520/555 (except the diff obviously, but that's covered in the 523/568 section) you can use this manual to service everything, 525/520/555/523/568.

Nice and easy if you have a few different cars from different years and you want to do trans work.

[jeff1234]

Chris, Check out my gallery for jeff1234, I have put some pictures of my trans, maybe you will find a picture or two to add to the FAQ. I dont know what you are able to do with them, maybe add some arrows and descriptions for certain parts. If they are no good, not to worry.
Jeff