'98 GMC 3500 Questions

burg226 · February 23, 2007

Hey guys,

Looking at purchasing a 98-99 3500 Sierra Dually 4x4 with ext cab or crew cab. Obviously i want the 6.6 Diesel. I love driving a standard transmission and can't stand an automatic deciding what gear i need to be in. So my question is can i get a SLE or SLT model with a 5 speed? All i can find is automatics.

Also can you guys inform me on a few other things? How much torque and HP are they stock? Do the 4x4 models come stock with a dif lock and skid plates? Any info or suggestions would be great. Thanks for the help.

k3500CC8.1 · February 23, 2007

Here's what I recall if memory serves correctly,

In 98-99 the 7.4L(454) was rated at 290hp and 410lbs. The Vortec 7.4L was introduced in 96 and available through the 2000 model. I owned a 96, 98, and 99 with the Vortec 7.4L and was never let down. Mileage unloaded was between 11 and 14mpg. Put over 230K miles combined on these three trucks and never had a engine or transmission problem.

I did have problems on the 96 and 99 with the rear axles seals leaking and destorying the rear breaks. Had them replaced 4 times between those two trucks and the problem always came back. I would have kept and stored the 96 if this problem wouldn't have been so persistent.

You had to order the skid plates and locking diff. on these models.

Available gear ratios were 3.73, 4.10, and 4.56. Almost all 1 tons I was around had the 4.10, a few 4.56 here and there. A lot of the 3/4 tons of that time were running 3.73s.

5 speed manual was available, I had one and 7.4L's with the 5 speed were quite availabe in those years every time I would run a dealer locator. But the majority were the 4L80E automatics. This is/was a very good trans. The 5 speed manual was available in the Silverado and SLT trim, even with leather buckets and center floor consule.

I never ran small blocks in my trucks so I do not have information on the Vortec 5.7L HD engine. I think they were around 250hp and 330lbs.

96 models had the better looking dask, due to the passenger side airbag not being present. I think GM screwed the look of the dash up either in 97 or 98 with the addition of the passenger side airbag.

6.5 liter diesel was availabe in these trucks put almost impossible to find after 1996. They developed a reputation (I had a 94 and 95 without any problems) and most dealers shyed away from carrying them in their inventory. Pretty much from 96-2000, heavy hauling GM 1 tons almost all ran the 7.4L's.

burg226 · February 26, 2007

Here's what I recall if memory serves correctly,

In 98-99 the 7.4L(454) was rated at 290hp and 410lbs. The Vortec 7.4L was introduced in 96 and available through the 2000 model. I owned a 96, 98, and 99 with the Vortec 7.4L and was never let down. Mileage unloaded was between 11 and 14mpg. Put over 230K miles combined on these three trucks and never had a engine or transmission problem.

I did have problems on the 96 and 99 with the rear axles seals leaking and destorying the rear breaks. Had them replaced 4 times between those two trucks and the problem always came back. I would have kept and stored the 96 if this problem wouldn't have been so persistent.

You had to order the skid plates and locking diff. on these models.

Available gear ratios were 3.73, 4.10, and 4.56. Almost all 1 tons I was around had the 4.10, a few 4.56 here and there. A lot of the 3/4 tons of that time were running 3.73s.

5 speed manual was available, I had one and 7.4L's with the 5 speed were quite availabe in those years every time I would run a dealer locator. But the majority were the 4L80E automatics. This is/was a very good trans. The 5 speed manual was available in the Silverado and SLT trim, even with leather buckets and center floor consule.

I never ran small blocks in my trucks so I do not have information on the Vortec 5.7L HD engine. I think they were around 250hp and 330lbs.

96 models had the better looking dask, due to the passenger side airbag not being present. I think GM screwed the look of the dash up either in 97 or 98 with the addition of the passenger side airbag.

6.5 liter diesel was availabe in these trucks put almost impossible to find after 1996. They developed a reputation (I had a 94 and 95 without any problems) and most dealers shyed away from carrying them in their inventory. Pretty much from 96-2000, heavy hauling GM 1 tons almost all ran the 7.4L's.

Thanks for the info. Can u explain why the 6.5 litre diesel was impossible to find, why dealers shyed away from them and what the reputation was? I'm going to look at a few different trucks this weekend and would like to make an educated decision. Thanks for the help.

k3500CC8.1 · February 27, 2007

I believe that the reason the 6.5 developed a reputation was due to the injector pump and a valve inside the pump. Most of dealers around my area would not order a diesel after the 96 model year unless it was ordered as a sold unit. I don't know if this bad reputation was justified, but it did exist.

The 94 and 95 6.5's I had would get between 14&15mpg unloaded. When I towed with them, the thing that really stunk was that a vast majority of the 6.5's came with 4.10 gears, and when combined with the very small rpm operating range of the 6.5's, well most of the time you were left pulling interstate grades well below the posted speed limit in 3rd gear(with the 4sp auto). If I remember right, 3rd gear topped out right about 63-64mph with the 4.10 gear on a GM 1 ton. I think that even with the 4.10 gears, the tow rating of a K3500 ext. cab was right at 7500lbs-8000lbs. Not real impressive. I think the 3.73 gears put you down in the 6500-7000lbs range. The tow ratings for the Vortec 350HD and 6.5L diesel were very close to each other. That's why everyone ran the Vortec 454, they needed to pull weight.