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Rear differential questions 9" vs 8.8

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Gary Lewis

Re: Rear differential questions 9" vs 8.8

Administrator

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.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Rembrant

Re: Rear differential questions 9" vs 8.8

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.

1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995

Gary Lewis

Re: Rear differential questions 9" vs 8.8

Administrator

I don't know how much play is acceptable, but will look in the shop manual tomorrow - if I remember.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Rear differential questions 9" vs 8.8

Administrator

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.

Gary, AKA "Gary fellow": Profile

Rembrant

Re: Rear differential questions 9" vs 8.8

Excellent info, thanks Gary.

Rembrant

Re: Rear differential questions 9" vs 8.8

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.

Gary Lewis

Re: Rear differential questions 9" vs 8.8

Administrator

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:

Gary, AKA "Gary fellow": Profile

Rembrant

Re: Rear differential questions 9" vs 8.8

Gary Lewis wrote

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.

Rembrant

Re: Rear differential questions 9" vs 8.8

In reply to this post by Gary Lewis

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.

Gary Lewis

Re: Rear differential questions 9" vs 8.8

Administrator

Cory - I'll look some more. Surely I can find it.

Gary, AKA "Gary fellow": Profile

Rembrant

Re: Rear differential questions 9" vs 8.8

Gary Lewis wrote

Cory - I'll look some more. Surely I can find it.

Gary,

Don't waste any time at all looking. I thought if it was something right at your finger tips, no big deal, but don't bother hunting for it. I can harass the guys at the Ford parts counter no worries at all;).

grumpin

Re: Rear differential questions 9" vs 8.8

In reply to this post by Rembrant

Rembrant wrote

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.

I had a 1987 Toyota Fourunner, the guys at the dealership here would run!

Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona

Steve83

Re: Rear differential questions 9" vs 8.8

Banned User

In reply to this post by Rembrant

Clip N804729-S11

Rembrant

Re: Rear differential questions 9" vs 8.8

Cool, thanks Steve.

Rembrant

Re: Rear differential questions 9" vs 8.8

In reply to this post by grumpin

grumpin wrote

I had a 1987 Toyota Fourunner, the guys at the dealership here would run!

Haha...god love them, I know they have a job to do, and they're usually busy enough they don't have time to be looking up obsolete parts for a guy like me, but sometimes the parts are still available. I just ordered a coolant temp sensor not long ago.

As soon as I say "1984", they let out a sigh and a groan like I just ruined 30 minutes of their day, and then they'll reluctantly start searching for my part. There is one guy at one of the Ford dealers that I'm convinced he doesn't even really look for me...he just sits at the computer for 45 seconds and then says it's obsolete...lol.

So, most of the time I try to find the part number online before I even go in there.

Thanks again to those that DO help! It IS appreciated.

Gary Lewis

Re: Rear differential questions 9" vs 8.8

Administrator

Well done, Steve!

I've searched and "N804729" doesn't seem to show up in the 1980 - 89 catalog, neither in the text part nor in the illustrations. I say "doesn't seem to" since I OCR'd the files and there's a chance that the OCR engine missed it or thought it said something else. But.....

Gary, AKA "Gary fellow": Profile

Steve83

Re: Rear differential questions 9" vs 8.8

Banned User

I'm not sure where I got that diagram & PN, but it looks like one of the Ford disks. I just changed computers, so I don't have any of them installed on this one yet to re-check.

grumpin

Re: Rear differential questions 9" vs 8.8

In reply to this post by Rembrant

Rembrant wrote

grumpin wrote

I had a 1987 Toyota Fourunner, the guys at the dealership here would run!

Haha...god love them, I know they have a job to do, and they're usually busy enough they don't have time to be looking up obsolete parts for a guy like me, but sometimes the parts are still available. I just ordered a coolant temp sensor not long ago.

As soon as I say "1984", they let out a sigh and a groan like I just ruined 30 minutes of their day, and then they'll reluctantly start searching for my part. There is one guy at one of the Ford dealers that I'm convinced he doesn't even really look for me...he just sits at the computer for 45 seconds and then says it's obsolete...lol.

So, most of the time I try to find the part number online before I even go in there.

Thanks again to those that DO help! It IS appreciated.

Fortunately I know the Ford parts guy here, he'll look for me. The guy he has helping really tries too. They had a guy there for awhile and I would ask for the guy I knew, if he was out I would say he's working on something for me and come back later.

You're right they're busy and such, but I used to work at a NAPA, and the guy who owned it would try everything before he said he couldn't get something.

Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona

Steve83

Re: Rear differential questions 9" vs 8.8

Banned User

In reply to this post by Rembrant

That clip was used at least through '96 (with the addition of a hole for the ABS sensor wiring retainer; and probably later) on all solid 8.8s (& possibly on later 9.75s), so it should be VERY easy-to-find in JYs. If yours are all rusted, I'm sure some of us can find them. I'll try to remember to look in my junkpile tomorrow...

Rembrant

Re: Rear differential questions 9" vs 8.8

Steve83 wrote

That clip was used at least through '96 (with the addition of a hole for the ABS sensor wiring retainer; and probably later) on all solid 8.8s (& possibly on later 9.75s), so it should be VERY easy-to-find in JYs. If yours are all rusted, I'm sure some of us can find them. I'll try to remember to look in my junkpile tomorrow...

Steve,

I checked with the dealer and of course the part is long obsolete. Anything from a junkyard will be rusted beyond use. There are two 1996 F150's at the junkyard I usually go to, and one of them is so rusty underneath that the M5OD crossmember is broken off the frame on the driver's side.

In any case, it's not a big deal. I'm just going to add one of those little rubber lined clamps to the end of it for the brake line. Nobody will see it anyway.

I'm ordering all new brake components hopefully today, so if all goes well I can get this stuff all buttoned up in a couple weeks.

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