1989 Bronco XLT 5.8L Rear Diff Leak

[UhDabbler]

Hello,

I was putting together my parts list for todays round of store runs and I needed to verify what rear diff gasket bolt pattern I needed (I believe this is the Dana55 8.8 inch) and I noticed a dark patch at the bottom of my cover (picture here). I haven't checked to see if its coming from my pinion seal or any other location on the diff yet.

I was wondering if anyone had recommendation on replacing all of the seals? Should I just replace the cover gasket if its only coming from there or should I replace all of them at one time and just top up for now? Also I have seen a few different things on identifying differential gear damage, any tips on things to look out for? Any oil weights in particular outside of the OEM manual recommendation?

To provide a bit more backstory on the truck as a whole:
176k miles
Previous 2 owners (my buddy had it before me and his uncle had it before him) didn't keep up on maintenance so I'm finding lots of neglect such as -
7 years between oil changes (I change that and the filter already)
U joints need replaced (still running factory)
mickey mouse wiring jobs everywhere
IAC valve has never been removed or cleaned (cleaned it yesterday, before picture here)
Last spark plug change was in 2012 (I have the new plugs and wires and will install after I solve the rear diff leak)
Potential Coolant leak (or just low, filled the reservoir and after 1 drive the tank had emptied but no moisture or signs of leaks anywhere, but regulates good consistent temp)
The K&N air filter they added has slight melting on the bottom and shows visible damage (new filter in transit)

The list continues but these are the primary functional issues I know of so far. All these issues I'm sure have gotten worse with me buying it (for $800 running) and then letting it sit for 4 years.

Thanks in advance for any and all perspectives and pieces of advice.

 

[miesk5]

Yo uh,
See 8.8 SEALS Replacement @ http://www.diesel-dave.com/vehic/manual/stj/stj50007.htm#extract_78

I forget if the 89 has a yoke or ******.

 

[UhDabbler]

Yo uh,
See 8.8 SEALS Replacement @ http://www.diesel-dave.com/vehic/manual/stj/stj50007.htm#extract_78

I forget if the 89 has a yoke or ******.

Thank you for the quick reply! This link is extremely helpful!

 

[UhDabbler]

**Update**
I am a doughnut. I had been working to get the back seat bolts out recently and had to use quite a bit of penetrating fluid to get them out and the latch assembly is directly above that rear pinion seal area. The fluid saturated the thick layer of dirt and made it look like it was leaking.

Unfortunately my transmission is leaking and the fluid is DARK. I haven't had any slipping but I will need to replace the large gasket at the front of the transmission im thinkin, and of course a fluid change.

 

[miesk5]

Yo U,
Dark brown or black fluid that has distinct burnt odor, indicates a transmission in need of repair or overhaul.
Odor may indicate overheating condition, clutch disc or band failure. Use an absorbent white facial tissue and wipe the fluid level indicator. Examine the stain for evidence of solid particles and for engine coolant signs (gum or varnish on fluid level indicator).
If particles are present in the fluid or there is evidence of engine coolant or water, the transmission pan must be removed for further inspection.

 

[UhDabbler]

Yo U,
Dark brown or black fluid that has distinct burnt odor, indicates a transmission in need of repair or overhaul.
Odor may indicate overheating condition, clutch disc or band failure. Use an absorbent white facial tissue and wipe the fluid level indicator. Examine the stain for evidence of solid particles and for engine coolant signs (gum or varnish on fluid level indicator).
If particles are present in the fluid or there is evidence of engine coolant or water, the transmission pan must be removed for further inspection.

I was surprised to say it doesn’t have a burnt odor, or at least not what I can tell when I smelt it. From the amount of floor on my garage floor I’d guesstimate in losing about a tablespoon a day.

Off to Montana for the weekend but I will inspect further this coming week. I’m thinking it’s probably time to rebuild or at minimum replace the clutches, seals, and toque converter.

 

[johnnyreb]

I was surprised to say it doesn’t have a burnt odor, or at least not what I can tell when I smelt it. From the amount of floor on my garage floor I’d guesstimate in losing about a tablespoon a day.

Off to Montana for the weekend but I will inspect further this coming week. I’m thinking it’s probably time to rebuild or at minimum replace the clutches, seals, and toque converter.

You might want to consider giving Green Sales Compant for some original Ford --USA MADE PARTS out of Ohio. 800-543-4959. Type it in your address bar and watch the videos.. they have alot of NEW OLD PARTS for any section of the vehicle your working on.

 

[Tiha]

Glad the rear end wasn't leaking. That is great news.

Might spray around the trans pan with some brake cleaner and make sure that is where it is coming from.

 

[miesk5]

Yo uh,
A quick fixer is the vacuum modulator, it's a vital component of an automatic transmission. It tells the transmission what kind of load is being put on it allowing the transmission to react with the proper line pressures and shift points. Over time, modulators can develop leaks, get ruptured diaphragms, get bent, etc. Not only can this cause annoying drivability issues, it can lead to premature transmission failure.
Also inspect it's hose, any signs of fluid or aroma thereof indicates it's diaphram ruptured.
BTW, ruptured diaphragms still haunt me!

Possible causes;
Cooler or its line is plugged causing quickly rising fluid heat.
Member ZIGGY wrote "If you have an access panel over ****** you might be able to reach the vent through the panel. The vent is pressed into the ****** and has a cap that should be loose on it (has a small spring under it). If cap is not loose, you will have to see if you can free it up, it's only crimped on and there a rubber gasket in the cap. You should be able to at least see if it is puking ****** fluid. Also check around your dip stick for leakage, if it is leaking, the O-Ring/packing is probably bad. In order to change it, you will have to remove one of the ****** housing bolts (top R/H bolt on pac side) that holds the dipstick tube. You will have to drain some of the ****** fluid first before you pull the dipstick or else it will drain out of the hole. Pull dipstick tube out and replace the O-ring/packing. I always put a bead of RTV around the tube just above the O-ring to help seal the tube." @ C6 leaking/ blowing ATF

Converter drainback check valve is intermittently failing to seat. If so, the converter drains half or more of its fluid back into the case, raising the fluid level and causing fluid to leak out, usually through the vent.

BTW, some add a vent hose extension, such as
Installation in an 89; Dana 44, 1356 transfer case, C6 transmission & Dana 60
Source: by Andrew K (Andy351, das panzer, sloppy seconds, the magic carpet) at FSB
Pics are gone so see them @ 1989 Ford Bronco Extended Breather Lines pictures, videos, and sounds | SuperMotors.net
Andy wrote, "my previous method of a ****** breather had fallen off, so i needed to get a male adapter to fit inside the ******'s hole.
i used some random silicone i had laying around, but it didn't hold. i ended up using krazy glue, which believe it or not worked.
the angle of the hose was not allowing it to hold in, so i used a 90* bend to get it right. the angle of the hose was not allowing it to hold in, so i used a 90* bend to get it right."

 

[ablediver]

"
Potential Coolant leak (or just low, filled the reservoir and after 1 drive the tank had emptied but no moisture or signs of leaks "

I've got a 90' (5.0) and a 96' (5.8). I've had the 90' 31 yrs. and it's been doing that same business of the expansion tank draining since I bought it in early 91'. The same goes for the 96' as well. No known etiology or cause so far... Go figure.
Ablediver out

 

[johnnyreb]

Hello,

I was putting together my parts list for todays round of store runs and I needed to verify what rear diff gasket bolt pattern I needed (I believe this is the Dana55 8.8 inch) and I noticed a dark patch at the bottom of my cover (picture here). I haven't checked to see if its coming from my pinion seal or any other location on the diff yet.

I was wondering if anyone had recommendation on replacing all of the seals? Should I just replace the cover gasket if its only coming from there or should I replace all of them at one time and just top up for now? Also I have seen a few different things on identifying differential gear damage, any tips on things to look out for? Any oil weights in particular outside of the OEM manual recommendation?

To provide a bit more backstory on the truck as a whole:
176k miles
Previous 2 owners (my buddy had it before me and his uncle had it before him) didn't keep up on maintenance so I'm finding lots of neglect such as -
7 years between oil changes (I change that and the filter already)
U joints need replaced (still running factory)
mickey mouse wiring jobs everywhere
IAC valve has never been removed or cleaned (cleaned it yesterday, before picture here)
Last spark plug change was in 2012 (I have the new plugs and wires and will install after I solve the rear diff leak)
Potential Coolant leak (or just low, filled the reservoir and after 1 drive the tank had emptied but no moisture or signs of leaks anywhere, but regulates good consistent temp)
The K&N air filter they added has slight melting on the bottom and shows visible damage (new filter in transit)

The list continues but these are the primary functional issues I know of so far. All these issues I'm sure have gotten worse with me buying it (for $800 running) and then letting it sit for 4 years.

Thanks in advance for any and all perspectives and pieces of advice.

Better get you a crawler if you don,t have one. You ,ll be spending some time on it. Make sure its comfortable and has a cushion on it. Also check all your yokes,sway bar bushings,axle bushing. As you are fixing one--you will notice alot that needs replaced. Good luck and be careful.

 

[ablediver]

Jonnyreb's right. Get a really good creeper. I 'm not talking the $29.95 over the $19.95. I'm talking around the $100 mark. Think of your weight and height and like Johnnyreb says, get a padded one with a headrest. You'll thank yourself for it later.
I bought the one below nine (9) years ago and it's a beast. Just my humble $.02 . Whatever works for you...

https://www.amazon.com/Traxion-1-100-ProGear-Wide-Creeper/dp/B007JYYPO2/ref=sr_1_31?crid=3SJA2MCQABXGM&keywords=heavyweight+creeper&qid=1662565545&sprefix=heavyweight+creeper%2Caps%2C107&sr=8-31&ufe=app_do%3Aamzn1.fos.f5122f16-c3e8-4386-bf32-63e904010ad0

Ablediver out

 

[Motech]

I was surprised to say it doesn’t have a burnt odor, or at least not what I can tell when I smelt it.

Originally filled with Mercon ATF, Ford killed that fluid around 1996 when they released Mercon V. If your transmission has been replaced or ATF has been changed in the last 25 years, chances are it's been refilled with the semi-synthetic Mercon V, or even full-synthetic Mercon SP or Mercon LV. These are all backward-compatible with original Mercon, and one of the advantages of the later semi and full synthetic fluids is extreme resistance to heat.

In brevity, they won't smell burnt. Go by the dark color, but not the odor.

BTW, ruptured diaphragms still haunt me!

Boy howdy! My harshest, most negative Yelp review came from a man had me chasing ATF leaks on his old Ranger. Fixed the pan gasket leak, he came back saying there's still some drips on his driveway. All I could find was a leaking shifter shaft seal, so I resealed that. (not a cheap fix either)
Two weeks later he returned saying it's still leaking. Up in the air it goes, but it's dry as a bone. Even showed him. I ask how big are the spots on his driveway. He says he doesn't see any, but he's had to add 3 quarts since his last visit.
Soy VAY man!
I let it down to check fluid level, fire it up and EE-YEOW! Big puffy, sweet-smelling grey plumes come billowing out the tailpipe.
I smack my forehead, tell him that his vacuum shift modulator has developed an internal diaphragm leak that is leaching ATF, which is being drawn into the vacuum hose and burning up in his combustion chambers. I tell him it's a $20.00 part, and if he can chill for a half-hour delivery, I will swap it out no charge and have him down the road in 45 minutes.
Bad things to say there. Between my forehead slap, the cheap part and the freebie offer, suddenly I had ripped him off with all the other fixes I performed. Leaks he had that he TOLD ME he had, and never once (til now) had the ATF smoke appeared!
Thing is, it had been so long since we had a vacuum-controlled shift modulator failure in the shop, I had plumb forgot to even consider that. Especially since he initially had me going after a leak, not excess ATF consumption.

Which brings me back full circle.

@UhDabbler -
Your Bronco came with two transmission options: C6 3-speed or E4OD 4-speed.

If you're running the E4OD, you will have an OD OFF button and no vacuum controlled shift modulator. Only the C6 has one, so don't go chasing one if it's the E4OD.

I needed to verify what rear diff gasket bolt pattern I needed

If you do still plan to pull that cover and service your differential, do not bother with a gasket. Industry standard, and now factory standard too, is to clean up the surfaces and reseal it with a bead of gasket sealer. Most will recommend silicone or RTV sealers, but I am a converted believer in Reinzosil 300 sealer by German company Victor Reinz. It costs a couple bucks more than the best silicone Ultras that PermaTex has to offer, but outperforms them all by miles.

 

[ablediver]

Motech,
Thanks for the heads up about REINZOSIL. I just looked them up on the ol' interweb and they have a whole slew of different type sealants. Kind of interesting to see a Euro company sending their products here. Hadn't seen that for a long time.

Ablediver out