Hope someone can shed some light on this matter. I bought a 98 about 10 months ago & up untill about a month ago when I hooked onto a 9,000lb. 5th. wheel, I loved the truck. About a 1,000 miles into the trip I blew an oil line on I-90 in Minnesota. After being towed in, 5er & all, the fellows that worked on this said that I must have a 95 engine. The fittings, they say, are from a 95 & not a 98. I read somewhere, I think a hummer site, that there was a surplus of blocks that were used in the later engines.? Has anyone heard of this? How would I tell? Are the engine numbers on the back side of the block, against the firewall? I would like to know how to tell if this truck had an engine swap & if this is going to be a lot of problems as per computer, performance, ect. P.S. The truck runs great w/out a load but performed lousy w/ the 5th. wheel.(no power & excessive smoke) I did discover thru this site that I had a bad wastegate solinoid & fixed that but have not had a chance to pull the trailer again so I dont know how it's going to perform. thanks, Larry

Oh, By the way, I cleaned the black paint off the valve cover from the detailing W/orange blast from Walmart & the Valvce cover says 95? Does thid mean anything or could it have been a short block from 95?

"95 blocks would have had the 0.500" fittings for remote oil filter - '98 would have 0.625" fittings.


'95 may be stronger block, with no piston oil-spray holes drilled into the weak main-webbing areas.


Piston oil-spray helps remove combustion heat


5288 or later inj pump won't be any problem on OBD-II system, all else is identical.


'95 turbo would be GM-5, '98 would be GM-8, on the rectangular casting label.