Gary Lewis Posted December 3, 2018 Share Posted December 3, 2018 Quick question on the 8.8 rear diff...or any factory rear diff for that matter: I was cleaning mine up today since I had it up on the bench...removing brake lines, etc. There was a hose on the vent...maybe 15-18" long...I didn't measure it. It was laying so that the open end was up around the driver's side brake wheel cylinder. Anyway...was there ever a little vent cap or anything on that end of the vent hose? Or was it just left open from the factory? Sorry, I forgot to take pics... Yes, there was a little plug, which the catalog calls "390312-S (PP— 102) plug (vent hose end)". I use a clear fuel filter to make sure critters can't get in there. And it goes up to the frame above the axle. Link to comment Share on other sites More sharing options...
Rembrant Posted December 4, 2018 Author Share Posted December 4, 2018 Yes, there was a little plug, which the catalog calls "390312-S (PP— 102) plug (vent hose end)". I use a clear fuel filter to make sure critters can't get in there. And it goes up to the frame above the axle. And there it is... https://www.ebay.com/itm/NOS-1985-1991-FORD-F250-F350-w-DANA-REAR-AXLE-VENT-HOSE-PLUG-390312-S-NEW-ORIG-/361902818453 $12.99, and $36.00 shipping for me...lol. I don't want it that badly, but at least now I know what was in there. I'll do the fuel filter trick, that'll work great. Thanks Gary. Another question on this 8.8 rear diff. I have the whole thing out and laying on a pallet and was getting it partially cleaned up yesterday. I grabbed the yoke, and there's a bit of slop when rotated back and forth. One immediately thinks that it's backlash between the ring and pinion, but I looked at a couple vids online, and the slop was almost all in the spider gears (open diff). They look like they're easy as pie to change. Anyway...no idea how much movement here is normal, but I'm going to pull the cover and check everything once I get the thing cleaned up and painted. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 4, 2018 Share Posted December 4, 2018 And there it is... https://www.ebay.com/itm/NOS-1985-1991-FORD-F250-F350-w-DANA-REAR-AXLE-VENT-HOSE-PLUG-390312-S-NEW-ORIG-/361902818453 $12.99, and $36.00 shipping for me...lol. I don't want it that badly, but at least now I know what was in there. I'll do the fuel filter trick, that'll work great. Thanks Gary. Another question on this 8.8 rear diff. I have the whole thing out and laying on a pallet and was getting it partially cleaned up yesterday. I grabbed the yoke, and there's a bit of slop when rotated back and forth. One immediately thinks that it's backlash between the ring and pinion, but I looked at a couple vids online, and the slop was almost all in the spider gears (open diff). They look like they're easy as pie to change. Anyway...no idea how much movement here is normal, but I'm going to pull the cover and check everything once I get the thing cleaned up and painted. I don't know how much play is acceptable, but will look in the shop manual tomorrow - if I remember. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 4, 2018 Share Posted December 4, 2018 I don't know how much play is acceptable, but will look in the shop manual tomorrow - if I remember. I can't find anything in the '85 FSM regarding the spider, or as Ford calls them "side", gear spec's. But the ring gear backlash is supposed be between .008 and .015" - measured at the ring gear. As for measuring at the companion flange, aka input shaft, they actually have you lock it via a pipe strapped to the companion flange and clamped to the frame. Then you are to put one wheel on the ground and measure the slop in the other wheel. When measured at 12" from the center of the axle the slop shouldn't exceed 1". Hope that helps. Link to comment Share on other sites More sharing options...
Rembrant Posted December 5, 2018 Author Share Posted December 5, 2018 I can't find anything in the '85 FSM regarding the spider, or as Ford calls them "side", gear spec's. But the ring gear backlash is supposed be between .008 and .015" - measured at the ring gear. As for measuring at the companion flange, aka input shaft, they actually have you lock it via a pipe strapped to the companion flange and clamped to the frame. Then you are to put one wheel on the ground and measure the slop in the other wheel. When measured at 12" from the center of the axle the slop shouldn't exceed 1". Hope that helps. Excellent info, thanks Gary. Link to comment Share on other sites More sharing options...
Rembrant Posted December 29, 2018 Author Share Posted December 29, 2018 Excellent info, thanks Gary. Gary, Would you happen to know what the part number is for this little bracket? It bolts to the top of the 8.8 rear diff, and the emergency brake cable fits in one end, and the hard brake line in the other. I'm sure this part was used well into the 2000's, if not right up to today (Is the 8.8 rear diff still in production?). I checked the junkyard, and I could see them on the diffs of mid-2000's pickups, but like everything else around here, they were all rusted to pieces. Can't see in the pic below, but mine is broken where the hard brake line mounts, and I want to order a new one. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 29, 2018 Share Posted December 29, 2018 Gary, Would you happen to know what the part number is for this little bracket? It bolts to the top of the 8.8 rear diff, and the emergency brake cable fits in one end, and the hard brake line in the other. I'm sure this part was used well into the 2000's, if not right up to today (Is the 8.8 rear diff still in production?). I checked the junkyard, and I could see them on the diffs of mid-2000's pickups, but like everything else around here, they were all rusted to pieces. Can't see in the pic below, but mine is broken where the hard brake line mounts, and I want to order a new one. Cory - That's a hard question to answer. Is it possibly this? It is all I can find. Any numbers on the part? If so, here's the part numbers: Link to comment Share on other sites More sharing options...
Rembrant Posted December 29, 2018 Author Share Posted December 29, 2018 Cory - That's a hard question to answer. Is it possibly this? It is all I can find. Any numbers on the part? Gary, no, that bracket is riveted to the frame. That's where the rear brake flex line attaches to the frame. I recognize that one because I removed mine and blasted it when I was cleaning up the frame. I'll see if I can find a picture of one installed. This bracket bolts right on the top of the pumpkin of the rear end. Link to comment Share on other sites More sharing options...
Rembrant Posted December 29, 2018 Author Share Posted December 29, 2018 Cory - That's a hard question to answer. Is it possibly this? It is all I can find. Any numbers on the part? If so, here's the part numbers: Here's a pic from the web. I put an arrow to point at the little tab/clip/bracket thingy. It holds the passenger side e-brake cable in the front, and the passenger side brake line in the rear above the diff cover. I'm sure I can get the guys at the Ford dealer to look it up for me, but as soon as I say the words "1984" to them, I can see their eyes gloss over and they lose interest very quickly...lol. This part should be the same all through the 1990's and well into the 2000's. Link to comment Share on other sites More sharing options...
Gary Lewis Posted December 29, 2018 Share Posted December 29, 2018 Here's a pic from the web. I put an arrow to point at the little tab/clip/bracket thingy. It holds the passenger side e-brake cable in the front, and the passenger side brake line in the rear above the diff cover. I'm sure I can get the guys at the Ford dealer to look it up for me, but as soon as I say the words "1984" to them, I can see their eyes gloss over and they lose interest very quickly...lol. This part should be the same all through the 1990's and well into the 2000's. Cory - I'll look some more. Surely I can find it. Link to comment Share on other sites More sharing options...
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