I just bought a 1997 3500,AT, Crew cab, 6.5. I know now that Chevy came out with the better version 6.5 kinda mid year with more torque, cooling etc etc. Which do I have?? My RPO code says "L65" which is 6.5L Turbo H.O. if that helps. I can't be sure if I have the two thermostats by looking.
Anyhow also...I have 4:10 gears with Posi. How do they differ from 373? Which better on Fuel?
How can I tell if I have the "3rd generation" injector pump?
Last of all...for now....which oil filter is best and which oil...Synthetic or what (I'm in CA, travel to Tahoe a lot). I don't care what it costs. Wix sport truck 51060 filter best?
Help a Newby out Guys, much appreciated!!Edited by: The Dude

You should be able to "see" your thermastat housing in the water crossover infront of the engine. the t-stat was turned vertically in 95-96 and doubled in 97.


The injection pump has a stanadyne tag facing the intake plenum. It should say 5288 or some higher number. The driver (PMD/FSD) will have a number also 34583 is third generation.


4.10's run well on 33x12.5x 16.5 or 285x75x16


Anything but fram will do on oil filtration, wix is good.


And as long as your using delvac or rotella or another HD diesel motor oil you'll be doing fine.Edited by: quantum mechanic

Used Fram filters every vehicle I've ever owned every oil change, I've never had a problem with them and I'll never switch. Synthetic oil or any CD thru CG4 rated oil will be fine. Your '97 will have the dual thermostat housing, easy to tell, the upper rad hose will come out of the tstat housing toward the firewall and curl around the A/C to the Rad. PMD model number should be easily visible on the driver's side of the pump once you get the 'Turbo Power' shield out of the way, and a mirror to see the tag on the back of the pump. Should say DS4831-5459 or 5521, basicly identical pumps, only difference is the stepper motor. 3.73 rears are generally better on fuel because you will run lower engine speeds, but as QM mentioned, Oversize tires will help, just keep in mind your speedo will read a little slow.

after a run in with the va state patrol(81 in a 65 towing) i had my speedo checked on a simple dyno here in richmond. my speedo is only off by +1 mph at 35, 45, 55, and 65. not enough to get me out of s**t.http://www.dieselplace.com/forum/smileys/Ermm.gif

Lumpey I feel your pain, gotten too many speeding tickets myself (as my insurance will gladly tell you). Once I flew past a cop while towing going about 87 in a 65 and he didn't pull out... I think he must've thought that it wasn't possible for my rig to be going that fast! So next time, just go faster! http://www.dieselplace.com/forum/smileys/Big Smile.gif

May be a dumb question, but why will the 285/75/16 oversize tire help me?

Win, When you go oversized, it lowers the final ratio (in overdrive)from 3.83 to 3.42 or something like that.

when you run larger tires, it takes less revolutions to run the same speed as before. less rpms equal better mileage. but when you have a lower final drive, pulling power is affected. but not too much to worry about.


cant go wrong with schaeffer's lubricants.


www.schaefferoil.com (http://www.schaefferoil.com), www.specializedlubricants.net (http://www.specializedlubricants.net)


Edited by: steiner43511

Thanks all you Diesel Dudes. I think I have the dual Thermostats but I'm gonna check with the dealer on Tuesday and see if they can absolutely confirm my engine specs.
By the way, one good tip:
Contact Chevy dealer about your own Trucks and request all service records be sent to you like I did (coming soon).