New For Me 1985 Silverado 20 6.2 Diesel

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Craig Nedrow

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First Name
Craig
Truck Year
1973 (have two), 1985
Truck Model
K10, K20, C20
Engine Size
350, 454, 6.2 Detroit
I am convinced that this truck has passed the reliability test. I drive it everywhere, handles and steers great with the new tires and alignment, it was out a bunch, back as well. It starts every time with the manual glow plug mod. It is cool, there for I to am cool by association, gotta developed that sneer for lesser rides, and she's purdy. Also I used to hate the 6.2, but I have had to learn about it and have a pretty good feel for it now. It seems to me with the 32' tires, 1:1 trans and 4:10 gears that between 55 and 65 is a good rpm. Actually 62 sounds best. 3600 is max rpm, so with 4.10 gears, 31.7 tall tires and a speed of 62, my rpm is 2811. When I get the over drive trans, (700r4, or 4l80e?) at 75 rpm's will be 2343. Going through parts of Idaho, Nevada speed limits are 85, so at that speed the rpm will be 2655. That is the same as the 3.075 rear end, interesting stuff. Oh yeah torque at 240@ 2000 rpm's, peak torque 275@2750, so in the ball park.
 

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mcarlo86

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Brian
Truck Year
1990
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Suburban
Engine Size
350
I am convinced that this truck has passed the reliability test. I drive it everywhere, handles and steers great with the new tires and alignment, it was out a bunch, back as well. It starts every time with the manual glow plug mod. It is cool, there for I to am cool by association, gotta developed that sneer for lesser rides, and she's purdy. Also I used to hate the 6.2, but I have had to learn about it and have a pretty good feel for it now. It seems to me with the 32' tires, 1:1 trans and 4:10 gears that between 55 and 65 is a good rpm. Actually 62 sounds best. 3600 is max rpm, so with 4.10 gears, 31.7 tall tires and a speed of 62, my rpm is 2811. When I get the over drive trans, (700r4, or 4l80e?) at 75 rpm's will be 2343. Going through parts of Idaho, Nevada speed limits are 85, so at that speed the rpm will be 2655. That is the same as the 3.075 rear end, interesting stuff. Oh yeah torque at 240@ 2000 rpm's, peak torque 275@2750, so in the ball park.
I have a 1990 K2500 with a 6.2 and 4.10's. It originally came with a TH400 auto and you are correct, about 60 mph was its sweet spot. I swapped in a rebuilt 700R4 with all the updates and having overdrive really made it an awesome highway cruiser. I was in the same boat as you and thought the 6.2's were junk until I got this one. It's definitely not fast, but the torque is decent and the fuel economy is great. I love driving it for sure. I have the same size tires as you also, but mine shows 2500 rpms at 70 mph. I am using the alternator for a tach signal and I wonder if the pulley is the wrong size possibly so it is showing higher rpm than actual?
 

Blue Ox

Turning Diesel Fuel Into Fun
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Derek
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MCMLXXXV
Truck Model
K20HD
Engine Size
6.2L
I have a 1990 K2500 with a 6.2 and 4.10's. It originally came with a TH400 auto and you are correct, about 60 mph was its sweet spot. I swapped in a rebuilt 700R4 with all the updates and having overdrive really made it an awesome highway cruiser. I was in the same boat as you and thought the 6.2's were junk until I got this one. It's definitely not fast, but the torque is decent and the fuel economy is great. I love driving it for sure. I have the same size tires as you also, but mine shows 2500 rpms at 70 mph. I am using the alternator for a tach signal and I wonder if the pulley is the wrong size possibly so it is showing higher rpm than actual?

We put a Gear Vendors in ours. It was like a different truck.

The Suburban had a 700R4. It was okay, but I wasn't as pleased with it because of the different ratios from the 400.
 

Craig Nedrow

NADAR UNDER THE RADAR
Supporting Member
Joined
Sep 1, 2018
Posts
1,035
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2,175
Location
Washington State
First Name
Craig
Truck Year
1973 (have two), 1985
Truck Model
K10, K20, C20
Engine Size
350, 454, 6.2 Detroit
Went to the Dr, and when I came out, truck wouldn't start. Luckily a fellow farmer saw my dilemma, had cables and got it started, God bless him. Sooo bought two new red top odyssey batteries, and man what a difference. Yes still have to use the glow plugs, but parked for ten minutes at the store, and came out and started without using the glow plugs, first time ever. Hope they last awhile...
 

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