I bought a complete used rear end out of a 1997 f-250, it's a 3.55 LS differential. I plan to put in my 1996 f-250 which has a 4.10 conventional differential. I purchased this one because I don't think it was the original. I am looking for better highway MPG so the LS was a real bonus.

I plan to use "Castrol Syntec" a full synthetic oil with a friction modifier in it.
Q1. Does this oil have a good reputation for this application, or should I consider others?

I read online that the axel bearings should be packed with grease as the primary bearing lubricant and the oil would serve as a secondary source. (When I pulled the hubs there was no sign of grease on the bearings.)
Q2. Is using grease considered a better idea?
Q3. If so, will I need to find a grease that is compatible with the synthetic oil?

Everything is out of the housing except the pinion and ring gear unit. I did remove the ring gear bearing caps, but didn't remove the ring gear unit. Everything was so tight and smooth and I wasn't sure if I would need to re-shim everything. The thing that surprised me was the bearing cap bolts broke loose with very little effort, as if they hadn't been torqued. I haven't been able to find the torque specs for these bolts.
Q4. What are the torque specs for these bearing cap bolts?

I have worked on all of my vehicles but I am not a Mechanic by trade. So.
Q5. Are there rookie mistakes that are typical for this rear end?
Q5. Any other advice?

 

Also, did you disturb the backlash between gear teeth? Lash (clearance) ought to be at least 0.010" measured at the outer edge of a ring gear tooth, at least the thickness of a typical mail-type postcard. Given you can "click" the teeth between one another, by hand, by gripping the ring gear and holding the housing stationary, through the clearance, you should feel a distinct "drag" due to bearing preload; not a lot, but the clearance should not be easily "clicked" back and forth. Am I not explaining my intent here very well?

Hope I helped! impish

 

First of all that is a Sterling 10.25. I think the 10.5 came in the 99+ Super Duties. Don't use any grease on the bearings. I can't answer any of your other questions, sorry.

 

My Ford manual says to pack the axle hub bearings with grease when replacing them or after an inspection. The grease will provide lubrication until gear oil can replace what was drained out of the hub during disassembly. As far as what type of grease, I would think as long as it is rated for wheel hub service it should be fine. When I replaced one of the hub seals I repacked the bearings with Lucas X-TRA Heavy Duty Grease. It seems to be working good, I also used it for the front hubs

Lucas X-TRA Heavy Duty Grease : Lucas Oil

 

Impish,
Yes, you did explain your intent well. I had to go out and pick up parts.
I am confident I didn't disturb the backlash between the gear teeth. When I took the bearing caps off I did pull "a little" but nothing moved, probably because of the bearing preload. That is when the little voice went off in my head that questioned the intelligence of what I was about to do.
Also I can still feel the drag due to the preload as you mentioned. I didn't know the backlash min. 0.010, so that will be good to know and I am sure it is at least .0625 that is my guess. Now if I can just fit my fat hand in there to check it.
Thanks for the info, Mike

 

Peter_X,
I did catch the mistake. The original post finally made it through on the third try which required re-typing it each time. I think I was going brain dead by then. I assume the 2 just didn't make from my finger to the post.
I finally found a post that came to the same conclusion as your post listed. They just used their gear oil on the bearings. I am a little concerned that the grease may not mix well with the synthetic oil.
Thanks for the post, Mike

 

ichabod40,
Thanks for the Ford info, I think I read to pack them on one of their links, I'm not sure. The other link I saw mentioned there is an ongoing debate about using grease or not.
I have that little doubt going on in the back of my head about the synthetic and grease mixing.
Thanks again for the post, Mike

 

Don't take that 0.010" lash figure to the bank! It's a minimum I picked out of my memory from working on zillions of Ford 9-inchers. 0.0625" is WAY TOO MUCH! Greater lash moves the contact pattern between the meshing teeth way too far out to the periphery of the ring gear! Plus, that kind of lash is bound to make ungodly noise. In general, if you hold the center section tightly so it can't move, grab the ring gear through a rag, and rotate the gears back and forth as far as clearance allows you to tell:
If all is fairly acceptable (and there is no dirt or grit present, just clean oil film), you should feel no roughness during that movement of parts. The gears meshing together should feel very smooth, as though the teeth are rolling over one another, not scraping. Any roughness felt is an indication of either improper tooth contact pattern, bad bearings either on the pinion or differential, or both. Silky smooth feel, ready to run! impish

PS: Feel the outer edges of the ring gear teeth for a razor-edge sharp buildup: this indicates improper gear set-up. Those edges are normally quite sharp to begin with, thus, the use of a RAG to keep blood out of your gearset!

PPS: Believe Ford designation IS 10.25" axle, but why split hairs?

 

Impish,
I did get the .010 = minimum but had no idea what the max might be. The .0625 is just an estimate off the top of my head from feel and the visual. It seems to be about the same as the one in my truck now. It has just under 170,000 mi. on it, and it seems good and is noise free as far as I can tell.

So now I understand I need to figure out how to get an accurate measurement on the backlash. It is currently on a bench in my garage so it is very accessible. Now is the time to correct any problem.

I did put lithium grease on the gears to check the pattern. It looked good to me but I didn't think to check the depth of the pattern. Maybe with a small mirror I will be able to check it. I did rotate it quite a bit both directions and it felt very smooth. I was turning it with the pinion yoke at the time and some with the ring gear.

I'll definitely check the ring gear for the for the sharp edge buildup you mentioned. I did handle the ring gear without a rag quite a bit but I didn't get cut or feel edge buildup. Tomorrow I will know that for sure.

Your right, it is 10.25 Sterling. I didn't catch the mistake until after I posted it. I tried to edit it but could only edit the message. That was my third time to retype the whole thing, I kept loosing it for one reason or the other. I know that "2" left my brain and went to my finger, but it never made it to the keyboard. HA!

I was thinking since your first post maybe I could lock the pinion in place and measure the movement of the ring gear. I just don't see me getting my hand and feeler gauge in the right place to check it.

I'll let you know more tomorrow. Thanks for all the help, Mike

 

Impish,
I checked the tooth pattern with white grease again knowing now more of what to look for and made a few of photos to post. The ring gear teeth depth measured .5" with my depth gauge. The ware pattern of the white grease measured .46". The rear end is upside down on my bench which may cause a little confusion. The forward tooth pattern is in the top of the photo. (inside the curve of the ring gear tooth.) The ware pattern still looks good to me but it's been 30 + years since I have done this.

There is no razor sharp or rolled edge on the ring gear teeth and the movement was very smooth to me.

Check out the photos and let me know what you think.

Thanks again for all of the help, Mike

PS. Sorry I haven't figured out how to attach a photo. I'll research it.

 

impish,
I did manage to build a bracket and mount it and my depth gauge to the housing and get a reading from the tooth movement of the ring gear. From multiple readings I got 0.011 to 0.0125 each time.

Looks like my sight / feel estimate wasn't very accurate. Not the first time!

I have tried the FAQ but the instructions didn't work for the photos. I may try a new thread as it mentioned, but don't have high hopes for it. If it does I'll post the new title here.

Thanks, Mike

 

To post photos it's easiest to use photobucket.com. Free hosting and you can creat private and public albums.

Good luck on the rebuild. Learning how to rebuild a rear axle and trans are top on my list.

 

83 Capril,
I think that probably the best way to go. I have been thinking about using one of the photo sights for my photography hobby. I just haven't made up my mind which one I would want to use. There is a lot of info and opinions about which ones are the best. Seems to depend on just what you need personaly. I just gota do it!

I got the rear end buttened up today and only need to finiah putting the oil in, paint it and rebuild the brakes. Shouldn't be a problem now as long as I didn't miss anything "IMPORTANT". I got the help I needed here (FTE) to check out the gear setup which is what I needed the most.

Thanks for everyones help, Mike

 

Lou.... Usually, if the "feel" of rotating the gears is quite smooth, the contact pattern will not be way off; or, in other words, a way out of whack pattern will generally give a kind of scraping feeling when you rotate them, especially if little or no lubrication is on the teeth.

The reason for turning them by gripping the ring gear instead of the pinion end, or yoke, is that this requires 3 or 4 times more torque (actually, the gear ratio) applied to make them turn, thus, accenting whatever "feel" there is.

Sounds like yer on yer way! Good luck! impish

 

Impish,
Thanks again for all the insight as to what and how to look for things while checking the set up on my differential. It has given me the confidence to move forward much quicker than I would have on my own.

My weekend is already full starting today so I will get back to it by Monday and hope to have it ready to install next week.

I was thinking of connecting a large drill to the pinion nut and running it to check for leaks, noises, vibrations, etc. Without being able to load it with resistance it may not tell much, but for me it will be worth the effort. The real test will be on the road @ 70 and the resulting MPG I hope to get. Time will tell.

Have a great weekend, Mike