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New 6.5 owner from metro Detroit

Messages
17
Likes
25
Location
Detroit
Thread starter #1
E3EB6279-1F0E-4F63-A1C6-3CE8E4B34AA1.jpeg 2D7BD853-7F93-4FE2-A1B1-D17E58440626.jpeg FCEA33A3-B55D-4A3B-AC31-3BD7D788F00A.jpeg Hello everyone, I bought my first diesel truck a few months ago ( 1994 gmc 3500 reg cab drw 2wd 6.5 turbo with 215k)
I’m really liking it so far, and have been trying to go through it as I’m able to get everything fixed or upgraded as needed. It already has the pmd relocated.

When I bought it there was a lift pump problem and bad vibrations at highway speeds and a nonfunctional wastegate on the turbo.

I have figured out the lift pump( oil pressure switch), vibration ( bad rear brake drums) and installed a turbo master to fix wastegate. I’ve been replacing all the fluids and filters with Amsoil one at a time and bought new tires all round.
I’m getting ready to do trans filter and fluid soon (4l80e) and want to address a harsh shift from 1 to 2 gear. Trans has been rebuilt and has a shift kit installed by previous owner. I’m thinking maybe the 1/2 accumulator is bad and would like any input on that.

Also it runs well and starts right up on the coldest morning with a tiny puff of white smoke that clears right up but I feel like maybe the acceleration and mileage should be a little better. I’m averaging around 13mpg with mostly city driving, and around 16 on the highway. I’m thinking the injectors might be original but I’m not sure. Does that sound like a candidate for new injectors?

Overall I’m really enjoying the truck and learning about diesel in general. It has a cool hydraulic bed cover some of you might get a kick out of. I’ll try to include some pics, thanks Matt.
 

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Will L.

Well-Known Member
Messages
8,203
Likes
7,532
Location
Boulder City Nv
#2
Welcome to TTS.

Mileage doesn’t sound as good as it should be.
Careful who you buy your injectors from- a lot of crap ones out there. Leroydiesel.com is a vendor here and well trusted for good parts at a fair price. If you get a new set from him, you can hold on to your old ones as a rebuild option for the future.

With that mileage on there check/ replace the harmonic balancer. I wont run them over 100,000 on these engines. Crank killer. Dont get the doorman or other cheap ones. AC Delco for the next 100,000 miles or best is a fluiddampr good for the rest of forever.
 
Messages
17
Likes
25
Location
Detroit
Thread starter #4
That’s kinda what I was thinking, mpg could be better. Original owner seemed to do a decent job documenting repairs and I don’t see anything about injectors. So it won’t surprise me if they are original.
As far as the harm bal goes, I looked it over recently and don’t see any problem but it’s definitely something I’ve been conscious of. Thanks
 

Jaryd

Love my 6.5
Messages
850
Likes
1,123
Location
Hodges, SC
#7
Welcome. Good looking truck you got there. I got one just like it but sadly it’s my parts truck. Got body and frame damage on front drivers side. I like the looks of the single cab duallys
 

WarWagon

Well it hits on 7 of 8...
Messages
8,526
Likes
3,144
Location
AZ
#10
Welcome.

Filters are more important than "the oil". Start by getting rid of the gravel screen K&N ring duster and put in a real air filter. Check the fender and see if the restrictive intake snorkel is still in there. With 2500 to 5000 mile oil changes on this engine synthetic, esp. Amsoil, is hard to justify in this dirty running engine. A good oil filter is justified. AC Delco oil filters are not good oil filters anymore with the Ecore, The Fram group is not, Purolator is not. (The Fram Group makes a lot of expensive brands now.)

Pull the oil cooler away from the condenser and clean out the mat of dirt build up there. Are the oil cooler lines stiff and leaking just waiting to blow out and take the engine with em?

MPG at what MPH? I can't break over 15 MPG esp. with the AC on. The Turbo master is not MPG friendly as the OEM system because the OEM system will open the Turbo Waste Gate during cruise. The Asthma Attack Small Turbo GM used will generate 6 PSI of boost from airflow alone without any fuel on. This is why the WG opening up to reduce unneeded boost can help MPG.

Shift kits... They shift hard ya know? Either slip the trans to near burn up with butter smooth shifts or risk hard parts with a quick hard shift. You are after all attempting to slow down a high torque diesel... I would reverse the shift kit and toss the weak OEM Torque Converter myself. The TCC clutch is the #1 thing I burn up. Seriously Trans problems DO NOT turn on the Service Engine Soon light. So check for any codes in the computer to see if something is causing a hard shift due to limp mode etc.

Do you plan to tow hard and heavy: Cooling systems, better turbo...
 
Messages
17
Likes
25
Location
Detroit
Thread starter #15
Welcome.

Filters are more important than "the oil". Start by getting rid of the gravel screen K&N ring duster and put in a real air filter. Check the fender and see if the restrictive intake snorkel is still in there. With 2500 to 5000 mile oil changes on this engine synthetic, esp. Amsoil, is hard to justify in this dirty running engine. A good oil filter is justified. AC Delco oil filters are not good oil filters anymore with the Ecore, The Fram group is not, Purolator is not. (The Fram Group makes a lot of expensive brands now.)

Pull the oil cooler away from the condenser and clean out the mat of dirt build up there. Are the oil cooler lines stiff and leaking just waiting to blow out and take the engine with em?

MPG at what MPH? I can't break over 15 MPG esp. with the AC on. The Turbo master is not MPG friendly as the OEM system because the OEM system will open the Turbo Waste Gate during cruise. The Asthma Attack Small Turbo GM used will generate 6 PSI of boost from airflow alone without any fuel on. This is why the WG opening up to reduce unneeded boost can help MPG.

Shift kits... They shift hard ya know? Either slip the trans to near burn up with butter smooth shifts or risk hard parts with a quick hard shift. You are after all attempting to slow down a high torque diesel... I would reverse the shift kit and toss the weak OEM Torque Converter myself. The TCC clutch is the #1 thing I burn up. Seriously Trans problems DO NOT turn on the Service Engine Soon light. So check for any codes in the computer to see if something is causing a hard shift due to limp mode etc.

Do you plan to tow hard and heavy: Cooling systems, better turbo...
Thanks for the input, I’ve had good luck with Amsoil over the years but I understand your sentiment about it being hard to justify in an old dirty diesel. I have to admit I was a little disappointed to see it turn black in the first 24 hours. That said I believe good oil and filters are important to any engine, I guess value is relative.
I’m planning to change oil hoses because they do leak a little apparently and I can’t stomach the thought of all my oil pouring out onto the freeway at 75 mph.
A better intake and filter is also in the plan book.
I understand shift kits make the shifts harder but I’m not sure what is normal or not. All shifts except first to second seem fine but that one two shift is pretty severe. I’m not experienced with transmissions but I’m a quick learner and love challenging myself. So I’ll give it a go when funds allow me to start chipping away at the list, it seems to grow faster than I can cross things off.
 

WarWagon

Well it hits on 7 of 8...
Messages
8,526
Likes
3,144
Location
AZ
#20
Thanks for the input, I’ve had good luck with Amsoil over the years but I understand your sentiment about it being hard to justify in an old dirty diesel. I have to admit I was a little disappointed to see it turn black in the first 24 hours. That said I believe good oil and filters are important to any engine, I guess value is relative.
I’m planning to change oil hoses because they do leak a little apparently and I can’t stomach the thought of all my oil pouring out onto the freeway at 75 mph.
A better intake and filter is also in the plan book.
I understand shift kits make the shifts harder but I’m not sure what is normal or not. All shifts except first to second seem fine but that one two shift is pretty severe. I’m not experienced with transmissions but I’m a quick learner and love challenging myself. So I’ll give it a go when funds allow me to start chipping away at the list, it seems to grow faster than I can cross things off.
K47 air filter option with OEM intake from a later year 6.5 diesel is the best frugal intake to get. Make sure any aftermarket isn't a hot underhood air intake and check the specs on the filter. Oiled band aid gauze ring dusters aren't going to cut it when there are better aftermarket filters out there. Paper does the job.

Yeah synthetic may have saved me a 6.5 engine I scuffed a piston in once. If you tow and run hard you will find Used Oil Analysis backs up the 2500 mile oil change in the owner's manual: it doesn't have 500 miles left in it! High soot, out of grade, wear metals high, and that's with adding a quart every 500 miles. 3000 miles gets me a phone call from the lab... Only way to clean these engines up for the oil is gapless rings:

http://www.thetruckstop.us/forum/threads/total-seal-gapless-rings.29135/
 
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