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Discussion Starter · #1 ·
It looks like my rear differential is leaking. I'm replacing it tonight.
1.- What kind of lubricant is this?
I'm reading the Hayes Manual and can't you believe it does NOT say?
It looks pretty simple to do. Drive 'til warm on 4WD and all gears, Drain, remove old and clean old gasket, replace gasket, and refill.

2.- Is there a front differential? No mention in the manual.

Any tips?
 

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It's just plain gear lube. You will not hurt it with plain 90-weight. Some mechanics are recommending the 90w140 synthetic now, but 85w90, 90wt, etc are all fine, as long as it is gear lube. There is a front differential. It takes the same fluid, just a little bit less of it. The drain plug on that is actually one of the bolts that holds the 3rd member into the differential (one of the bolts that holds the diff together). The fill plug is on the front of the diff. Always remove the fill plugs before you remove the drains. That way if you can't get the fill plug out, you won't be stuck with a truck that you can't move because it's differential is empty.

What part is leaking? The gasket around the diff cover?

-Tad
 

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Discussion Starter · #3 ·
Thanks Tad. Very Good Tip as well.
Yes, I looks like the bottom gasket of the diff cover. It's not dripping heavely and there is no oil marks in my driveway so I think I'm okay. I wish I had noticed earlier. I'm going 90W140 synthetic, this truck is a keeper.

Thanks again
 

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You don't really need a gasket. I just did this on the wifes 98. I just used rtv on both mating surfaces and I also used the mobil one 75-90 synthetic gear oil. And oh yeah don't forget to use a tube/bottle of the LSD additive if you have the limited slip option.
 

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If you have a limited slip differential, then you need to use the additive that lubricates the clutches.

I would say if you have a second gen you probably have a limited slip diff.

Jack up the rear tires and spin one tire. If they both spin the same way then you have a limited slip diff. If one spins one direction and the other spins opposite then you have an open diff.

Real good site for those that want to learn how stuff works:

http://auto.howstuffworks.com/differential.htm
 

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Discussion Starter · #7 ·
Thanks Bigpoppax2. I will look for this as well as the store tonight. If I get hits right You recomend to use 75x90 syntheric Oil (this is basically the only gear synthetich weight that I found at PepBoy last night.

Don't want to sound stupid but Do I mix this with the 75x90 synthetic oil? or I check to see if the gear oil already comes with it?
 

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Steps you need to take.

Find out if you have a limited slip or not.

If yes buy 2 bottles of the synthic gear oil and a bottle of LSD additive, if not just buy the synthetic gear oil.

Drive your truck for a while 5-10 miles (probably to the parts store) to heat the gear oil up. This will make most of it come out easliy, and carry any oilborne crud with it when it goes.

Take out the fill plug.

Put an oil drain pan under the diff.

Remove the drain plug. (first gen)

If you have a second gen, instead of having a drain plug you must remove the inspection cover. (This is what you can use RTV silicone to seal back up later.) (sec gen)

Clean the cover and the rearend housing where the cover came off. (sec gen)

Run a small bead of RTV silicone on both surfaces. Let them sit for about 4-5 minutes. (sec gen)

Put the cover back on and start all of the bolts. Then tighten all of the bolts to factory spec. (sec gen)

Put the drain plug back in (first gen)

Now add the LSD additive through the fill hole (both gens)

Next add the gear oil through the fill hole till it comes out of the hole. (both gens)

Replace the fill plug and wipe off the housing.

That's it. Took about as long to type this as it should take you to do this project.
 

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No problem. Just a hint you should go to your profile page and type in what you drive; year, tranny and what mods you have done. This will aid those who wish to help you. I would have known which set of instructions to give you.

I think you have a second gen which you will find you will need to use a 3/8" ratchet to get your drain plug out. I'm pretty sure it's a 3/8" square.
 

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Discussion Starter · #11 ·
Bigpoppax2 you have FAILED ME !! hehe just kidding bro. I finished everything went well.
One item that needs to be included in the instructions will be to:
2.- Loosen/ remove the track bar left hand side (I removed the nut from the leftside).

This must be done otherwise you won't be able to take the diff cover off.
Really easy. I took my time doing it since I didn't want to screw it up. How much is this normally? I would love to know how much I save. I spent like $20.oo and my own time.

Now ....next project how hard the the front Differential?
I can not believe Hayes Manual does not say anything about this or what type of oil I should used.

Thanks again. Take care
 

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Actually when I did this on my 98 you can do it without taking the trackbar off. You just have to drop the cover as far as it will go then tilt the bottom of it toward the engine and it will rotate out.

The front is about the same. Should have a fill/drain plug instead of a cover on it like the rear.

Next you can do the transfer case oil. It takes 10W30 motor oil. You will need to buy a fluid pump to do the transfer case. It has to be pumped into the transfer case.

Sounds like you took care of it. Good job.
 

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We had to add this lubricant to our 95 Rodeo and learned something. The first time we did it, we still had the "klunk" noise. I bought the lube at an auto parts store. This time I called Isuzu and wanted to buy it from them. They were out of it, but the guy told me to go to any GM dealer and get it. That is what they used. Headed to my local Pontiac garage, added it. Since then, not a peep.
 

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From what I understand about the clunk, it's the slip yoke that needs a shot of grease. My 98 does it some I will grease the yoke and see if it makes it quit for a while. It'd be nice to have a grease fitting there. 8) May just have to install one.
 

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We have a 1999 Isuzu Rodeo with just 104,000 miles. Dropped it off at a garage today and they said our differential needs replacement. Parts and labor $1100...is this car worth repair and is this a good price for New Jersey area?

Thanks all.
 

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I would say no, you could get a junkyard axle complete and have a mom and pop shop install it for you if you are not able to do the swap yourself. Just make sure your ratios are the same. You either have 4.10 or 4.30 gears.

I am seeing lots of rear diff's for a 4 wheel drive Rodeo for $100 on junkyard sites. Surely a local garage can do an install in a few hours tops. Should run a total of 500 max?
 

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Where in New Jersey are you, I will see if there is anything close to you that's a good deal.
 

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It's a 4 cylinder according to sig, so it will be 2WD. Not sure about 2WD, but my 4x4 Amigo has 4.77s with the 4 cylinder.
 
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