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Isuzu Owners Maintenance and Repair



  • I bought a bottle of additive from my isuzu dealer and it was actually a GM product. I also bought the diff oil from them for $8/qt. I promptly returned it when I discovered they sold me GL-4 instead of GL-5 like the manual calls for. I also found Castrol diff oil for $3.50/qt at Advanced Auto parts so the choice was not difficult. Another thing that made me a little nervous about my local dealer was when the parts guy asked the mechanic about the LSD additive and he said "I never use it". I'll stick to doing my own maintenance!
  • breakorbreakor Posts: 398
    The official Helm Trooper service manual for 1999 is what I was quoting, page OB-12 to be exact. Since the topic was the rear that is the spec I was noting. There is a different chart for the front.
  • Thanks for the reply, I'll have to get a Helm service manual for my 02. Sounds like useful info. Any ideas about MSG# 2673?
  • FYI, the local dealer in Houston uses only 80W-90 (maybe Castrol) in both differentials. Oh, and greetings to you, jimmmyp!
  • wildbucwildbuc Posts: 88
    Just wanted to say how much I appreciate these responses from fellow Trooper owners. So far my rear differential seems to be doing fine with the 75W90 weight Mobil One oil and GM additive. I'll continue running my Trooper this way unless I hear noises. Thanks.
  • WildBuc,
    I had a non limited slip rear diff in my 1995 and I let the shop change the oil and they put in the limited slip addititive. I made them change it again at no charge for the labor because they did not follow my instructions not to use the additive.
    I am not a lubricant or fluids expert, but by the time you hear a rear diff problem, there can be quite a lot of damage. For the really low cost of another change of oil, you will not have to worry.
    If you do have problems with lubricant usually that shows up as too much friction and therefore heat. It is winter now and you might not notice heat or the diff oil smell that should come with a hot diff because it might not get hot enough in winter.
    Damage might be happening. Compare the cost of one more oil change to the rear diff to the cost of replacement. I think it is not worth finding out the hard way.
    At least consult an oil expert. There is a help line you can find on
     where you call directly to a knowlegeable oil person and IMHO your situation warrants a call. If you do call, please post what you find out.
    Thank You
  • sdavitosdavito Posts: 71
    Greasing the spline on the drive shaft is what cured your clunk.

  • paisanpaisan Posts: 21,181
    It's ok to put in LSD additive in a non-LSD, it's the other way around that causes a problem.

  • wildbucwildbuc Posts: 88
    Boxtrooper has got me spooked for sure. I'll contact Mobil 1 and Redline and will post their responses when I hear from them.

    Keep'm rolling
  • bluedevilsbluedevils Posts: 2,554
    are folks concerned because he used 75W90 and that may be too thin, or concerned because he used a GM spec LSD and this may be the wrong stuff to add?

    There was a similar discussion a while back and I believe I mentioned back then that I decided to use the 75W90 Mobil 1 synthetic gear lube in my 98 Trooper's rear differential, and I don't recall anyone warning me that this could be a big mistake.
  • wildbuc's diff has Mobil1 which already has limited slip additive included and it has the GM limited slip additive also. So a double dose of limited slip additive. If it were my diff I would worry about two things:
    1.) two different additives getting along together
    2.) having removed another 1/4 to 1/3 of the slipery gear oil to make room for the extra bottle of friction additive.
    I just wanted to make a point that the cost of the two quarts of oil is so low and easy to install that any slight chance of not having the right oil in there is worth changing it.
    I do not think that synthetic 75W90 is going to hurt the rear differential, but I do think that the thicker 80W140 Redline I used will protect my rear diff better than 75W90 especially for towing. I also want to make the limited slip clutch plates last as long as the vehicle so if the thicker oil is specified then I will use it.
  • wildbucwildbuc Posts: 88
    Boxtrooper, my thinking was that Mobil 1 did not have LSD additive in it. This may be true but sure far I haven't found any clear mention of it. This might be something I have overlooked, but I should know soon when Mobil 1 contacts me.

    Regarding percentage of LSD additive to amount of gear oil used, the Trooper requires 3.2 quarts, so I don't see where replacing 4 oz. of oil with additive means that 1/4th to 1/3rd of the oil is being replaced, even accounting for the the amount of additive already in Mobil 1.

    As far as cost goes, the 4 quarts of Mobil 1 75W-90 at Autozone went for about $7. each. The GM additive costs $9.95 for 4 oz. So, I have about $40. invested.
  • bluedevilsbluedevils Posts: 2,554
    I was not aware of this and had assumed the opposite when I decided a while back to use Mobil 1 75W90 gear lube in our 98 Trooper. Where does this information come from? I don't recall seeing any mention on the bottle that a limited slip additive was part of the formula or that additional limited slip additive was not necessary due to the formulation of the Mobil 1.
  • bluedevilsbluedevils Posts: 2,554
    ok, time for me to fess up to yet another stupid thing. Added 1/4 qt oil on Weds eve, discovered a puddle of oil on garage floor Friday eve. Called wife who was driving truck home. She pulled over and checked dipstick. The filler cap was in the engine bay, but was not where it should be. I.e., I had forgotten to screw it back on. Truck was about a quart low. Wife added a quart and proceeded home.

    I'm not that worried about the truck having been driven 50-100 miles while a quart low; that does not seem like a major problem. But does driving while the oil filler cap is off do anything bad?
  • breakorbreakor Posts: 398
    By nature most synthetics typically don't require the friction modifier additive.

    Here is a quote from the Mobil 1 site - Recommended for many limited slip applications. For certain high level LS applications, additional limited slip additive may be required if axle chatter is observed. 140_SyntheticGearLubricant.asp

    Here is a quote from the Amsoil site - AMSOIL Synthetic Gear Lubes do not require the use of this additive. However, not all differentials respond the same and if chatter is noticed, the addition of AMSOIL Slip-Lock will eliminate it.
  • breakorbreakor Posts: 398
    I suppose if you splattered enough you could set yourself up for a fire. Otherwise I suspect all you made was a mess. I suggest you clean off what you can to prevent dirt from sticking everywhere as well as minimizing the chance of an oil fire. I would use some liquid cleaner and a rag rather than a carwash hose. I am just leary about putting water under the hood what with all the electronics. Just my hopefully helpful $.02.
  • cptsessocptsesso Posts: 116
    I had this done to me before by none other than the dealer. It just makes an oily mess. They added the lost oil, I believe a half quart, and attempted to clean it up. They did not do a good job so I sprayed it with gunk engine cleaner and hosed it off.

    I always clean my engines. Never had one single electrical problem. Just don't blast the areas where the electronics are ie:fuse box, etc. Use low pressure to clean around these areas.
  • bluedevilsbluedevils Posts: 2,554
    I'm going to clean up as much of the engine compartment as I can with Simple Green. Thanks for the advice.
  • jtk152jtk152 Posts: 139
    You will draw (dirty) unfiltered air into the engine driving without the oil cap on. The PCV system will not function at all with the oil cap off. Not that big a deal since you caught it right away, but I wouldn't stretch this oil change interval too far. These engines will throw a ton of oil out through the fill hole. The cam gears spin just below the fill hole & sling oil upwards. The left side of your engine bay must have been a mess!! Glad to hear you got it early!
  • I left the oil fill cap off once back in the 1980's on my 1984 Trooper 1.9L engine. I was on a cross country trip and had added some oil since it burned 1qt/1000 miles or so and the trip was 1400 miles. The thing that made me notice the oil cap was off was a dark line moving slowly up my fender toward the drivers side rear view mirror. Oil was hitting the hood and blowing out the edge of the hood onto the fender and getting close enough that I could see the oil while driving. When I opened up the hood I found the oil cap stuck to the hood because I had set it down on the air cleaner cover on top of the carburator and the hood pressed onto it when closed. I put in another quart of oil and finished my trip by stopping at one of those coin operated car washes to clean up the mess.
  • bluedevilsbluedevils Posts: 2,554
    it wasn't as dirty as I feared, especially after hearing my wife's description over the phone. I was surprised and relieved to learn that it had lost only a quart. Very lucky.
  • wildbucwildbuc Posts: 88
    I just got a response from Mobil 1 regarding using GM LSD additive with Mobil 1 75W-90 oil in my Trooper.

    A technician from Mobil 1 said that would be fine.
  • wildbucwildbuc Posts: 88
    I was reading on another Isuzu forum that some owners are having blown engines due to oil failure around 60K miles. Anybody here have a Trooper 98-2000 that has gone farther without engine problems?
  • raydahsraydahs Posts: 449
    I could see that happening if they don't realize that these engines burn oil and they're in the habit of checking the oil only on occasion. On my 99' I have 92K miles, since 12/24 I've been driving back and forth from San Diego to L.A. daily (300 miles). I'm getting concerned because I'm now burning 1qt. every 1000 miles. My gas mileage is still at 17 mpg/hwy though. One thing I noticed while filling up again, was the tail pipe has a Black soot around it, which is new. I looked at other cars, which also have the soot, maybe it's the Winter blend of gas?
  • beer47beer47 Posts: 185
    So far so good, almost at 110,000 miles. I have done MB1 oil changes every 10K. I am going to change that to every 7500 though to coincide with my 7500 tire rotations. Has been a gem so far.
  • bluedevilsbluedevils Posts: 2,554
    98,517 miles. Changed the oil 5 minutes ago. Have had no engine 'problems' except for the high oil consumption rate, which now stands at a quart every 900 miles or so. It's more of an annoyance than a problem, in my book.
  • sdc2sdc2 Posts: 780
    I would look into having the EGR system cleaned. Clogging in the EGR tube and valve reportedly can dramatically and abruptly increase oil consumption, which can catch you off guard.
  • sbcookesbcooke Posts: 2,297
    I have a lot of soot on my exhaust. I have a '99 also. I only have 35K on it though and have a very short commute. I burn very little oil.

    I notice a fair amount of water coming out of exhaust on startup, so I always have to allow for some idle time to protect the exhaust with my commute being so short.

    I am getting really poor mileage 10-11 MPG around town, but I attribute that to a very short commute, roof rack, larger tires, and additional weight from Bullbar. If I remove the roof rack I have gotten just over 17 on the highway, so I assume it is just the way it is.
  • wildbucwildbuc Posts: 88
    I have 43K mileage on my Trooper with no problems. I'm using Mobil 1 10W-30 oil and change around 7K miles. I use about a quart of oil every 5K miles. I get 19-20 mpg on the road but I drive very conservatively and run higher pressures in tires.
  • wildbucwildbuc Posts: 88
    Has anybody done this and can give a good explanation how it is done? I'm sure many Trooper owners would like to know.
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