6.2 diesel , sm465 4 spd. , 4.10 gears.... Wheres the sweet spot ??

[hotsam]

Im thinking of setting my 6.2 diesel in my dually.. For reasons of fuel economy..As title states its 4 speed and 4.10 gears (235/75/16 tires) The only trucks ive driven are the military trucks with 4.56 gears or trucks with the 700r with overdrives. Never 1:1 with 4.10s..So those of you that own them, what can i expect to run comfortably without screaming or being against the governor while driving highway trips? RPMs at say 65mph. Many thanks.. My big block does great and I know will out-perform the 6.2 but i mostly use it local so im thinking local fuel economy

[Tiger Joe]

my math says that size tire (roughly 30" tall) with your rear will be just under 3k rpm at 65.

"most" engines like to be somewhere around 2000 rpm, which would be where you were at closer to 45 not 65.

I just bought a 6.5 turbo diesel with the nv4500 and I can tell you I would NOT want to drive that thing on the highway without OD. mines a 3500HD with 4.63 gears, and is great around town in 4th, but would definitely miss OD if I didn't have it

[GM72K10]

Got an 86 K30 dump with the 6.2, 4 speed and 215 85 16 tires. Good fuel economy and will do 60 no problem. Great for plowing snow also.
Drive the CUCVs which I have had and have a few. I would NOT be cruising at 65 in stock condition.

[DieselSJ]

Peak torque on the 6.2 is around 1800 RPM. This is also the speed where they cruise most efficiently. My Jeep has 3.31 gears, 235/75/15 tires with a 700R4 and that puts me in a good spot for cruising 65-70 in overdrive.

[Tom]

That setup is a whole lot of NOPE. If I can't cruise at 80mph at less then 3000rpm its not a driver but an in town tool.

[hotsam]

Thanks for the replies !! Thats what I wanted was some real experience to base on.Yeah.. I have had a couple of the military trucks with 4.56s and 400 turbo trans and I couldnt imagine trying to run interstate speeds with them. I wasnt sure if the 4.10 ratio would free it up enough. With those responses I believe im leaning more to keep my big block..OR figure out how to convince my wonderful wife how badly WE need a Gear Vendors overdrive unit for OUR truck 😁😏 It would even make the Big block fuel economy better... I think im on to something here !!!

[D13]

6.2 + 4L80E = big grin. If you must shift, NV4500.

[Tiger Joe]

personally I wouldn't give up a 454 for a 6.2

if you start looking for OD, i would swap the NV4500 in. since you already have a stick, you could do the swap relatively cheap.

[SunSoaked]

In the process of dropping this into my 85 k20 with cucv (4:56) axles.

[74CustomK20]

My 6.5 in my 98 is at 2500 rpm around 78ish mph. I really wanna put in a GV unit but so expensive!

[Edahall]

The problem with the 6.2 diesel is this:

Horsepower / Torque: 130 hp (97 kW) @ 3,600 rpm / 240 lb·ft (325 N·m) @ 2,000 rpm

What a huge sacrifice for saving fuel.

[GM72K10]

J code in CUCVS
Engine: 379ci (6.2L) Detroit Diesel V8 engine
Power: 155*hp (116*kW) @ 3600 rpm
Torque: 257*lb·ft (348*N·m) @ 2000 rpm

[hotsam]

Originally Posted by GM72K10

J code in CUCVS
Engine: 379ci (6.2L) Detroit Diesel V8 engine
Power: 155*hp (116*kW) @ 3600 rpm
Torque: 257*lb·ft (348*N·m) @ 2000 rpm

Hey nice to know... Now i gotta go out and check the vin on the doner cucv that my 6.2 came out of !!!!! Thanks for the info

[D13]

Let's face it, the 6.2 was designed to be a diesel that matched the 305 in power.
Add a turbo and get a mild 350.

6.2's are great engines for light toting around. Not so much for towing although I see a lot of the 1 tons with them.

[hotsam]

Originally Posted by D13

Let's face it, the 6.2 was designed to be a diesel that matched the 305 in power.
Add a turbo and get a mild 350.

6.2's are great engines for light toting around. Not so much for towing although I see a lot of the 1 tons with them.

Haha !!! Well the 305 comparison does it for me.... Looks like any diesel swap in my 3+3 will have to be CUMMINS !!!! 👍😎

[Edahall]

Originally Posted by hotsam

Haha !!! Well the 305 comparison does it for me.... Looks like any diesel swap in my 3+3 will have to be CUMMINS !!!! 👍😎

Yup, highly recommend the Cummins 6BT 12 valve over the 6.2L diesel. I get the same fuel economy with both engines but the Suburban with the Cummins is lifted, 4 wheel drive and 3/4 ton. Both get upper 20's cruising at 62 mph but Cummins gets better fuel economy towing and much more power. 6.2L had to run at near red line to develop any power, Cummins pulls like crazy right off idle. I'm also half ways to 1 million miles on the Cummins. 6.2 does not have as long a lifespan.