Tell me what you know about a 1998 GMC Sierra 4x4 Diesel...

[Christian P.]

I may have the opportunity to get a 1998 GMC Sierra 2500 Diesel - long story.

My previous experience with these trucks was not so good - we had 3 of them in Western Africa and I got stranded twice when the rear axle broke in two parts (on 2 different trucks). I think ours were the earliest models (1994)

Are-these truck somehow reliable? What about the diesel engine? Is this a 6.2 or 6.5? I did a bit of research but it was not clear to me.

Anything specific I should be worry about?

[locrwln]

It will be a 6.5 turbo. I can't remember which site is "the" site for 6.2/6.5 tech. Anyway, it seems there are a lot of people that say really good things about them and some that say only bad things about them. I know there are a few things that the pros recommend to do to make them last. Most that have good luck with them report 250k+ on mileage. The tranny (if auto) will be a 4l80e and an NV4500 if manual. No where near cummins/powerstroke/duramax power, but relatively decent fuel mileage from everything I have read.

I do have a question, were the trucks, that you broke axles on, 1500's with 10 bolts, 2500's with a 14bolt semi-float or 2500's with a 14 bolt full float? I can see the 10 bolt breaking (pretty easy), surprised if it was a 14 bolt SF and downright shocked if you broke a 14 bolt FF.

Jack

[omaha_rick]

from my research, the 6.2 / 6.5 family was designed for fuel milage. it wasn't ment to be near a cummings, powerstroke, or duramaxx. it was just a more fuel efficient option to the 350. little less h.p. little more ft/lbs. i dont think they even had as much ft/lbs as the big block in compairable years. now, i am not badmouthing, i personally like these engines

that truck would be a 6.5L as the 6.2L wasn't available after '93 or '94. the main problem with a 6.5L, that i'm aware of, is injection pump failure. some I.P.s had aluminum internals and seemed to not fail, i was told it hasn't had an I.P. by 150xxx miles it would likely never need one. otherwise they fail about 90xxx-120xxx miles, due to plastic internals. and all the GM replacement I.P.s have plastic internals. apparnetly there was no rhyme or reason to which engines got 'good' pumps or 'bad' pumps (i.e. day of the week, early or late prodution, ect.) that being said, i have seen aftermarket I.P.s that claim to not have problems because the electronics were removed from inside the pump (inside the engine) to a remote location (fenderwell or firewall) but i have no experince with these, i only know they exisit. kinda like the diet Dr. Pepper guy on T.V.
i also know that I.P.s cost about $900 from the dealer and GM flatrate pays 9-10 hours, so replacement is expensive. at least compaired to my income.

this info came from multiple 6.5L owners / previous owners, and a GM Goodwrench mecanic in west central IL farm country who has worked on countless 6.5L diesels. it is acurate to the best of my knowledge. hope it helps.

other than that, i love this body style GM. i have a '89 in process now, with a 6.2L. and have had a few other variations in the past.

peace
-rick

[Rot Box]

I had a 95 6.5TD and loved/hated it. Great mileage comparable to my first gen Cummins and really good power once you upgrade to an unrestricted exhaust and intake. I had a few problems that really pushed me to sell it back in the day that now (ten years later) I don't think were too big of a deal.

I could write a novel here but I'll touch on some of the main issues that you could be faced with motor wise.

1. Injector pump. After 93 the pump was electronically controlled and I feel GM did a great job matching the DS4 pump to the motor no complaints there. However the Fuel Solenoid Driver (about the size of a deck of cards) was placed on the side of the pump in an effort to keep it cool. This was a poor design and often these drivers would fail from excessive heat giving the same symptoms as a failed Injector Pump. The only fix I found was to relocate the driver completely OUT OF THE engine bay. The other kits that put it on the intake housing actually create more heat I know becuase I have a heat gun and verified it. The only kit that moves this part correctly is the one from Heath Diesel. I believe the injector pump should last 100k miles or more reliably imo.

2. OPS. The oil pressure switch is prone to failure but they are easy to change so keep one in the glove box and understand their function. Once they fail you may or may not ever know until you go to start the motor after shutting it off. Hard starts or no starts and a hesitation at high rpms are the symptoms. There must be oil pressure for the fuel lift pump to turn on and supply fuel to the injector pump. It took me awhile to figure that one out (DOH)

3. Broken crank. The cranks on these motors are tough, but a defective harmonic balancer will cause them to weaken and break over time. Feel around on the balancer often and check for cracks in the rubber. Some last a long time others split and loose balance often without the driver noticing.

4. Cooling. You'd be good to go here. Early 96 and older had a poor cooling system. A 98 will have all the upgraded high flow pieces just make sure you replace the water pump with the same year pump and not an earlier one! A 99-00 cooling fan is well worth the money if you tow a lot. I talked to Bill Heath and he said the 6.5 heads have been know to crack at anything over 217* DON'T overheat this motor LOL.

5. Glow plugs. Replace ONLY with the OEM plugs and nothing else. Cheap plugs like autolites or champions will burn out quickly and often swell on the end making them extremely difficult to remove.

6. Oil leaks. Get used to them or buy the upgraded lines/hoses.

Anyway thats all I can think of at the moment. The 2500 will have a really strong axle whether it is a light 3/4ton or heavy. Also both transmissions (auto or manual) are winners if you keep them healthy. Good luck if you have any specific questions please hit me up I'll try my best to help.

Andrew

EDIT: www.thedieselpage.com (buy their books!)
www.heathdiesel.com
www.kennedydiesel.com
^ these guys have seen it all and are a wealth of info.

[Bullseye240]

Here's "the site" for the 6.5:
http://www.thetruckstop.us/forum/forum.php
I'm a member there and can tell you you will get all the help you need without any B.S. I have a 94 6.5 turbo Blazer with 225000 miles on it and have no intention of ever getting rid of it. Go to the Truck Stop and look around.
Cheap to maintain once you fix the factory screw ups.

[Christian P.]

Thanks guys for all the feedback. I just bought a house and will need a truck during the remodel phase. This one is part of a package...and the price makes it really hard to skip.

It has 113K, auto, no rust, all power package, new tires and seem in really great condition. I will keep you posted.

[shortbus4x4]

I currently own a 96 K3500 with a 6.5 and manual trans and owned a 93 with a 6.5 and auto trans. You put much of a load on them and they are gutless going up hills. They go, just not fast. I think the first gen Dodge Cummins gets better mileage and has more power but the entry price is more. For the design of the 6.5 they are good engines, you just have to realize what they were designed for. Relocate your pump driver module, take the plastic engine cover off, and get a bigger exhaust and air intake for power and longevity. Also make sure your fuel lift pump is working, its down on the frame rail under the drivers door. Without a good supply of diesel and the right pressure your injection pump won't last long. Its the same design as the VP44 pump on the 24 valve cummins. I prefer the manual trans behind the 6.5 because it seemed like the auto trans sucked up more power. If you offroad much get the mechanical front axle actuator, I have seen a few times where the electric one fails at the worst time. Oil cooler hoses like to leak also. SSdiesel supply is another 6.5 hotrod vendor. I modified the wastegate on my turbo for a little more boost but you need to have a pryo and boost guage before you do that. I also have a big exhaust system with flowmaster downpipe which helps. You can get some marine injectors for a little more power too. Make sure you change the fuel filter on a regular basis and add some conditioner too. I did about 7k miles on my filter and towards the end noticed a lack of power so I changed it and got my power back, must of got some dirty fuel somewhere.

[bdbecker]

My uncle has one with the manual transmission and has 200k+ miles on it. He used it as a DD and to tow his 5th wheel camper all over the place until he replaced it with a newer truck that has the Allison transmission. When he was showing me his new truck, he talked about how he couldn't bring himself to part ways with the old one because it never let him down. He still has it for his work truck/DD, and as far as I know, he's had no major issues except for the injection pump failure that Rick mentioned earlier. It looks like hell from all those years of use, but he does take good care of his stuff from a mechanical maintainence perspective.

[dragogt]

I may have the opportunity to get a 1998 GMC Sierra 2500 Diesel - long story.

My previous experience with these trucks was not so good - we had 3 of them in Western Africa and I got stranded twice when the rear axle broke in two parts (on 2 different trucks). I think ours were the earliest models (1994)

Are-these truck somehow reliable? What about the diesel engine? Is this a 6.2 or 6.5? I did a bit of research but it was not clear to me.

Anything specific I should be worry about?

Before you go to "kick the tires" arm yourself with so good info..

http://www.thetruckstop.us/forum/sho...f-Diesel-Rides

http://www.thetruckstop.us/forum/showthread.php?t=21858

http://www.thetruckstop.us/forum/sho...hnical-Library

[87GMCJimmy]

That is a really good looking 2500!!! I've always liked that body style!