Hi everybody, just looking for some advice on an 8.8 rebuild. I am rebuilding my rear and installing 3.08 gears. The gears I have are used but look absolutely mint. I bought a rebuild kit with all new bearings, races, shims etc. I've installed all the new bearings and races and everything seemed to go together just fine. The install of the pinion went pretty well too. We set the preload on the pinion to about 16 inch lbs and it feels nice and smooth as it spins. Now, when I set the carrier in I can get my backlash to about .014" I believe .008-.012 is the acceptable range. I've found that I can spin the pinion with the carrier in place and it will spin nice and free for about a turn and a half and then it feels like it binds a little. I've checked the run out on the ring gear and found a variance of .002 +\- which I think would be acceptable. Has anyone ever run into this before? Is it possible I am feeling a bit of the previous wear pattern in the gears? I'm at a loss and frustrated to say the least. I certainly appreciate any insight anyone can offer.
Were these gears in this housing before or did you buy them separately? What does the contact pattern look like on both the drive and coast sides? If you have bind when you turn the pinion, it is not gear wear, it is a bearing issue. With a runout of 0.002"+/-, these gears were likely operated on worn bearings. Your backlash should be closer to 0.010". Your gears wont last long, and will be noisy at 0.014" I do not like used gears. A new Ford 3.08:1 gearset is $155.
With that backlash and runout it shouldn't be binding... at a minimum it would be at .012. Did you turn the pinion all the way thru without the carrier installed?
They were separate of the housing when I bought them. The contact pattern appears the same as i've seen in past experiences but that's not saying much. Do you think it could be possible I have the carrier shimmed too tight and its binding the bearings?
You need to re-shim the carrier to tighten up the backlash, and then paint marking compound to check the loaded contact pattern. Post pictures.
If you had the carrier tight enough to be binding you wouldn't have .014 backlash. I would pull the carrier back out, verify the pinion has the same amount of drag thru a few turns. Then measure your shims before setting the carrier in place. If the one on the ring gear side is thicker than the other one..... swap them, even if it creates a lot of backlash. Turn it thru and see what it does. These are pretty easy to build ( I have done a bunch of them when I worked at the dealers) and if you are having a problem.... start over! See what the backlash is by putting the thin shim in the ring gear side. If it spins freely, measure the backlash in at least 4 places around the ring gear. One more thing to look at while the carrier is out....... make sure the ring gear is seated on the carrier all the way around !!! Easy mistake to make !
Another question..... how did you select the shims for the pinion? This is more critical than the backlash when setting one up (that is why there is a "window" for backlash.... not so much on the pinion depth).
Ok, I just pulled the carrier out (again) and verified the pinion spins smooth throughout about a million rotations. I re- shimmed the carrier and got my backlash to .009 in 4 places. Still have the bind tho. I see your bringing me back to pinion shims, this is almost definitely where I'm screwed up. What do you suggest for selection or a measurement for the pinion depth?
You either have to use a specific tool, or use the marking-compound method. One requires a special tool, the other, finger paint. This will show you the contact pattern. The contact pattern will indicate the pinion depth. Here's a good video:
I just looked in my factory manual.... there is no spec for pinion depth listed. You use the special tools to select the shim by sliding shims between gauge block and tube and find one that has a slight amount of drag. What I have done before is remove the shim from the original pinion and install it on the new pinion, set the backlash (which is .008-.015) and then check the pattern and adjust from there.
That's exactly what I'm going to do, use the old shim as a starting point. I should have done that to start. My own worst enemy sometimes. Thank you for all the help. Very knowledgeable. You guys really make this forum head and shoulders above any other.
Did you 'block sand' the back of the ring gear? Block sanding removes residue from oxide used to treat the gears, if you have used gears block sanding will remove the raised ridge around the bolthole. Shouldn't the pinion be about 25inch pounds for new bearings? 15inch pounds for used? The pinion bearing tolerance won't affect what you are dealing with.
Let us know how thick the shim is you have in it and what shim was on the old pinion. Another thought on the binding... if the pinion is too deep, it can actually come in contact with the carrier and drag (seen this happen with worn pinion or carrier bearings also). I need to see the pattern on the coast and pull side.... can't tell from that photo.
Well I had a .020 shim on the pinion. I went to .032 and this is the pattern I have: I am at .009,.009,010,and .009 on the back lash. It seems to doi with less bind but I Still have a spot where I feel more resistance when I turn the carrier over with the pinion.
See if you can isolate the spot where it is binding. Mark the pinion and ring gear and roll it thru again and see if it duplicates in the same spot every time. There may be a burr or a nick on a ring gear tooth (not thinking pinion because you mentioned turning it 1 1/2 turns before you felt it).
Well after wasting several days with this bs I decided to buy another set of carrier bearings and installed a carrier out of another 8.8 I had. Used my ring gear from the first one and bingo. It's absolutely perfect now. I have still not found what exactly was wrong with the original carrier but two sets of carrier bearings and God knows how many hrs wasted I don't care enough to find out anymore. I appreciate all the help from everyone.
I have never tried it, and was always told not to do it..... don't use a pinion out of one gear set with a ring gear out of another set. It will work, but you don't know how much noise it will make. Gears are sold in a set because the 2 gears have been honed together as a set to keep noise at a minimum.
I set up many R&P over the years when I worked at the local Ford Place. But now don't have access to the set-up tools. Had a 3.08 rearend and needed a 3.55 and just bought a whole rear end with a 3.55. It was $100 off Craigs List, Cheaper than a new R&P and quiet.