Differential Condition, water in it...rebuild it, inspect further or leave in?

[blueday]

Hi,

I'm going through typical maintenance on my 1990 GW while I'm doing the lift, brakes, steering components wheels/tires and so on. So I found the front diff had what in it at some point. As you can see when I drained the fluid it was milky and looks like the diff cover was halfway filled with oil and the top half either was filled with water or had heavy condensation on it to rust that much. I did notice there was grit in diff case and no telling how long it's been in there. The rear diff oil was not milky at all and pretty clean, gears were not as rough looking either.

That said, looking closer at the spider gears they look a bit rough and scarred. I can catch my finger nail on the inside of the gears. What’s your opinions on the condition of this as far as rebuild it, inspect further or leave in?

I'm on the edge of just pulling both axles and having them rebuilt/geared and maybe adding a limited slip or just go for some lockers. The gears in there are 2.72's if I understand correctly on the ring gear numbering. I'm running stock 15" rims with 32" m/t's. Plan on pulling center console boat and so on. Just trying to figure out if I should do this now or see how it runs and maybe do it later and/or justify spending the money as we all probably do.

Ryan

[tgreese]

Open differential with some water in the oil. Happens a lot with Jeeps that get into deep water. Not a big deal. Front differential is more tolerant of wear and condition since the rear axle conveys most of the power.

I'd suggest you check your axle vents are mounted as high as possible and actually going to the axles. There will be rubber hoses from the axle tubes to the body somewhere. Covered here before - search old posts for more.

No pitting seen, seems ok. I'd wipe out as much of the bad oil as possible, close it up and refill. If you want, you could spray with some carb cleaner or such and wipe, or a pump oiler full of solvent, but I probably would just wipe out what I could see and reach. The 85W90 generic dino oil from Walmart in the gallon jug is what I'd use. Drive it some, change it once or twice until there's no more milkshake stuff.

"49 18" tooth count is 49/18 = 2.72. Is it 18 or 16? Either is quite tall for those tires and how much frontal area you added with the tires and lift.

[blueday]

49 18 on the ratio. Yeah I agree on the gear vs tire/lift. I'll probably start an LS/LT swap later this year so i think it'll come down to swapping gears now or later.

I haven't driven it around with new tires. With the older stock size tires it was already a turd driving around the neighborhood which is why I'm very tempted to just remove and have someone rebuild. Previous owner ran the vent to the charcoal canister. I'll double check to see if plugged by any chance. Previous owner didn't mention he changed diff oil so I'd assume the water was in there for a while.

[Stuka]

Your diff looks fine to me (Assuming bearings are all good). There was not enough water to cause damage to the gears. The spider gears show average wear for a vehicle of this age. Give it a good clean out with brake clean before putting it back together if you are going to regear it down the road.

The 32's will be tolerable with 2.73 gears, especially with you living at low altitude in a flatter area.

If you are going LS swap, will you be doing an overdrive transmission? If so, regearing will be a must. Without it you will need to be going extremely fast for it to shift into OD. 3.73s would be a good match with 32's and overdrive though.

[why_rick]

aside from the diff, jeep looks great! What lift are you using?

[Srdayflyer]

thats what my rear pumpkin looked like, my rear vent hose was torn out prior to me getting the vehicle when i opened the rearend thats what i found, also check your yolk for play, if you have any ay all the pinion bearing is shot or if you have a lot of play between fwd/reverse with a loud clunk/thump it needs rebuild ,the cover being half rusted tells me that it stood a long time and the oil drained off , i have seen that a lot in front ends as most of the urban cowboy 4x4ers dont engage the front axel from time to time and lube the front end with that mud soup you illustrated i would highly consider a rebuild as you dont want to get stranded in the back country. thats my 2 cents

[blueday]

Thanks for the responses. If I can find someone locally to rebuild them I'll go ahead and gear swap them and probably throw some more $ at them adding lockers. With the tire size, lift and future ls swap I don't think I'll regret it.

I thought it'd have a decent gear ratio because it had a "jeep" hitch on it when I bought it but after digging further it doesn't have the wiring for it (well it's there, just not done right), no transmissions cooler (i think they came with them from the factory?) and the obvious the gearing.

[blueday]

aside from the diff, jeep looks great! What lift are you using?

Thanks,

I went with the BJ's 4" lift on all corners with new socks, new steering components and so on. Lift came in last week so hopefully I'll get to them soon.

Ryan

[blueday]

Long shot, but are there any other factory dana 44 options that'll somewhat easily fit on the 90 grand wagoneers?

[rocklaurence]

If your sticking to 33" tires or smaller, Id invest in a TCI 2000 stall converter. It's much cheaper than re-gearing and keeps your engine in it's torque window. However, if your into moderate 4 wheeling, Lockers are the single biggest improvement you can make.

[Srdayflyer]

regarding the factory trailer wiring goes, there should be a 5 or 6 pin plug that supports a relay box that mounts on the rear cross member where the spare tire attach bolt is, you have to run a brake wire from a controller you need to install to the rear bumper and wire a 7 pin socket if you need pictures let me know

[tgreese]

... had a "jeep" hitch on it when I bought it but after digging further it doesn't have the wiring for it ...

A little more detail on the wiring.

I recall there were two possible trailer harnesses from the factory, a light-duty and a heavy-duty. The light-duty tapped off the existing wiring and was just wire and a five-pin flat connector hanging from the chassis. The heavy-duty type uses a relay box that takes its power from the tailgate window power wire. It uses a round 7-pin connector mounted on a bracket from the bumper. The '78 TSM on the Tom Collins site shows these harnesses well, with enough detail that you could duplicate them. The trailer connectors are a standard RV item. You'd likely need to replace the connector to the Jeep - I'd use a waterproof connector like a Duetch or Weatherpac, or clip out the dangling connector and wire direct. No need for that connector if you are not working on the assembly line.

https://oljeep.com/edge_parts_man.html

TSM.png

[blueday]

Thanks for the information on the hitch. I didn't see any kind of box described here and in other past posts when I searched. Previous owner had a 4pin connector hangin down with bare wire showing and they used those scotch lock connectors to pull signals from the harness to the connector. Autozone sells a $18 module that'll convert the left turn, right turn, brakes and running lights to a 4 pin connector so the turns and brake signals are shared. I cleaned up/cut back all the mess of corroded wires due to the scotch lock connectors and spliced into the factory harness and used some marine heat shrink to seal up the connections. I also had a spare 7 pin connector so I cut a piece of angle to mount it. I'll wire in the rest of the signals for the 7 pin if I ever need it.

I posted this for anyone looking for information in the future. Here's a picture of the hitch that was on it. I just cleaned it up, repainted and done.

Ryan

[tgreese]

Anything "Jeep Special Equipment" is almost certainly aftermarket. These accessories are sold across the Jeep dealership parts counters, and carried the Jeep logo. Usually they are a third-party product (Orrville here?), with Jeep providing a distribution channel and something of a blessing as "Jeep approved." If not owner installed, typically this stuff was installed at time of sale and mixed in with whatever financing the buyer needed. Good profit engine for the dealerships.

Just sayin', it likely has nothing to do with the rest of the Jeep, and does not imply any packages or such.

IIRC, the 7-pin connector gives you an electric brake connection. I'd guess that's the main reason why the Jeep 7-pin connector taps off the heavy tailgate motor wire.

[candymancan]

Thats the first pic ive ever seen showing the v style hitch weight capacity the stickers are always gone. Thanks for that. Did you hitch come with the 1/4 inch thick frame stifners that go inside the C channle.. i cant tell from your pic but it looks like you dont have them ?? . Did you also add the center bolts that go above against the Jeeps cross member. Hidden behind the bumper ? There should be two bolts there too.



Tgrease, The wagoneers of the past in the 70s were rated for 7500lbs of towing with a 401. it says it right on the specs sheet website for every year make and model of the fsj. These Jeeps were rated for that with that engine.. Todays standards it might sound too much but for back then its what cars pulled. A 360 in the GW is really not enough power as the Jeep struggled pulling ny j10 up hills. But for a 401 with 255hp in 72-75 and 220hp in 76-78 it was more than enough.. over the 360 145hp on a GW.. or 175 on a 70s wagoneer.

I have the same exact v style hitch i got from a 78 cherokee chief on my 90GW.. and it pulled my 76 J10 home 300 miles just fine minus lack of power up hills. But for load and sway at 60mph which i had none. I didnt really notice it back there when pulling.. Total flat bed trailer weight was 6400lbs. With about 300lbs of weight in the back of my Jeep (transmission transfercase brush guard etc)


Fyi my 90 alao has the big black trailer brake box in the back. My Jeep originally had a hitch but someone removed it in the past ? Anyway.. when i did the 7 pin to 4 pin adapter for the uhaul trailer.. my turn signal lights didnt work. If i wiggled the wires going to the box it did.. so i have a lose connection in that box somewhere.

I just bypassed it by feeding off the brake and turn signals for a 4 pin

[blueday]

Not knowing much about jeeps and the wagoneers, I'm glad the sticker was still on there too. I actually taped over it when i painted hitch just to keep it on there.

Yeah i had to replace the bolts (grade 8) because they were mismatched metric/standard and 1 of the center bolts were mia.

Do you have a picture of the frame stiffeners? I do not have them back there and actually plan to tow my 20ft center console boat with it.

Thanks

Ryan

[Stuka]

The hitch being rated for 7500 does not mean the vehicle is. The hitch was universal and put on as factory equipment for any Wagoneer or Cherokee with a tow package. The J-Trucks had a different hitch. Actual tow rating depended on which engine, brakes, gears, and transmission the vehicle had.

And back then there were not any tow standards. Manufacturers could say whatever they wanted. Now we have the SAE J2807 standard that most manufacturers follow. An FSJ (or any year) would likely only be rated to tow FAR less going by its standards.

Personally I have towed 3000lbs with an FSJ and that was sketchy enough to not want to do it again. Now, I do live in the mountains, and likely in the flat lands its less of an issue. Just be aware that a Wagoneer is very narrow, short, and with hardly adequate brakes. Though a 90 will have a front sway bar and trac bars, which will certainly help with stability.

[tgreese]

To me, factory equipment means installed at the factory. Unlikely the factory hitch would have the Special Equipment sticker that's hidden after installation. Likely dealer installed, or by the customer. "Jeep Special Equipment," as described above.

[candymancan]

The hitch being rated for 7500 does not mean the vehicle is. The hitch was universal and put on as factory equipment for any Wagoneer or Cherokee with a tow package. The J-Trucks had a different hitch. Actual tow rating depended on which engine, brakes, gears, and transmission the vehicle had.

And back then there were not any tow standards. Manufacturers could say whatever they wanted. Now we have the SAE J2807 standard that most manufacturers follow. An FSJ (or any year) would likely only be rated to tow FAR less going by its standards.

Personally I have towed 3000lbs with an FSJ and that was sketchy enough to not want to do it again. Now, I do live in the mountains, and likely in the flat lands its less of an issue. Just be aware that a Wagoneer is very narrow, short, and with hardly adequate brakes. Though a 90 will have a front sway bar and trac bars, which will certainly help with stability.

Weird i towed the 6400lbs on the uhaul up the mountains in va. And back down.. I had no sway or any issue at 65mph. Besides lack if power going up the hills. But hey thats you. This is me. Apples an oranges. The uhaul trailer was very stable. Brakes were fine on the Jeep with the trailer surge brakes.. The later year ones are rated for 5klbs. A ZJ is rated for 6500lbs fyi.. And the ZJ is lighter.. and even more narrow. But maybe its because i have a 90 like you said. I also have stiff springs rated for higher than factory loads. The 97-402 for 1440lbs. Vs the 1300lbs springs.. and an add a leaf as well sooo

The frame stiffners looks like these. Ill get more pics off mine

[candymancan]

Another pic of it. You see the end of the v style hitch bolts into the bottom of the stiffner and that plate has 1 bolt on each end into the frame c channle. Its a 1/4 inch thick plate nearly. Stiffens up the c channle and transfers more load to it as well i imagine

Id had to measure it exactly though