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Diesel review [message #296877]

Mon, 07 March 2016 12:12

Hal StClair

Messages: 971
Registered: March 2013
Location: Rio Rancho NM

Karma: -12

Senior Member

Just got back from a 2100 mile jaunt with the GMC so thought I'd give a little report on how the Diesel performed. We have almost 3000 miles on the conversion now. The first 1200+ miles of this trip were with the cruise control 'not home' so it may skew the numbers slightly. We had our toad with us the whole time also which does make a difference in both economy and performance of course. The last 830 miles from Quartzsite through Phoenix, up I17 to Flagstaff and then through to the Grand Canyon and on home to Albuquerque included a number of 7000'+ and a couple of 8000'+ passes. We averaged just shy of 13 mpg on this last leg with cruise working which 'seems' to be about .5 mpg better than without but sooo much nicer to drive.
Pulling the grade out of Phoenix in 95 degree weather did show an issue I have to address though. The fan clutch doesn't want to engage early enough so some slight tweaking of that will be needed. I sure wish there was an electric or air fan clutch that would work on these engines. The military H1's used a hydraulic clutch but incorporating one of those now would be a nightmare.
I think I'll also install a fan on the engine oil cooler as the temps get higher than I like at times.
Overall I was very pleased with the way it ran. I'd hopped for a little better fuel economy and maybe going with a slightly taller final gear would accomplish that but pulling a toad would probably be a 'white knuckle' affair with much less gear. 60 mph comes at about 2100 rpm now. If I come across a differential with the taller gears for REAL cheap I might be tempted but for now 14 mpg solo isn't too shabby.
Hal

(the guy that just can't leave things

"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane." 1977 Royale 101348, 1977 Royale 101586, Diesel powered, 1974 Eagle Bus 45',w/slideout, Rio Rancho, NM

[Updated on: Mon, 07 March 2016 12:14]

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Re: Diesel review [message #296879 is a reply to message #296877]

Mon, 07 March 2016 12:33

Neal Krisher

Messages: 54
Registered: November 2013
Location: Apple Valley, MN

Karma: 0

Member

Hal - What stinky engine do you have in yours? How loud is it?

"Life has no instruction manual. Parts and labor can be impossible to find. Many go down the road with parts that are in need of service. A breakdown is eventual." 1975 26', TZE165V100301 Project/Driver 1977 26' TZE167V100439 Parts unit

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Re: Diesel review [message #296890 is a reply to message #296879]

Mon, 07 March 2016 16:42

Hal StClair

Messages: 971
Registered: March 2013
Location: Rio Rancho NM

Karma: -12

Senior Member

It's a 6.5 diesel and the noise isn't bad with all the sound deadening materials in place.
Here's some pictures if you're interested.

http://www.gmcmhphotos.com/photos/u42137-hal-stclair.html

Hal

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Re: Diesel review [message #296895 is a reply to message #296877]

Mon, 07 March 2016 17:19

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

Great report Hal. That is quite a feat of engineering you have there. As for the noise issue, I heard it run, at idle - cold, and it was surprisingly quiet. Hal is very detail oriented and didn't leave much to chance. That's why he only has a couple of items on his punch list after such a major undertaking.

Were you able to maintain a decent speed on those grades on I-17? I am usually in 2nd gear going between 40 and 50 up those (miles long) hills. That is towing an '03 four door Tracker.

Carl Stouffer '75 ex Palm Beach Tucson, AZ. Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member

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Re: Diesel review [message #296899 is a reply to message #296895]

Mon, 07 March 2016 17:52

Hal StClair

Messages: 971
Registered: March 2013
Location: Rio Rancho NM

Karma: -12

Senior Member

Carl S. wrote on Mon, 07 March 2016 16:19

Great report Hal. That is quite a feat of engineering you have there. As for the noise issue, I heard it run, at idle - cold, and it was surprisingly quiet. Hal is very detail oriented and didn't leave much to chance. That's why he only has a couple of items on his punch list after such a major undertaking.

Were you able to maintain a decent speed on those grades on I-17? I am usually in 2nd gear going between 40 and 50 up those (miles long) hills. That is towing an '03 four door Tracker.

Carl, I was able to keep the speed about the same but the darn fan clutch didn't want to lock in fast enough for my liking so I backed off a bit. It would drop out of overdrive and bounce up and down between 3rd and 4th although 3rd mostly on the tough spots. The PCM will pull fuel when it heats up so even with 10 lbs of boost it was a bit lazy. Then again, those are some pretty good grades. The EGT's with the inter cooler never exceeded 900f post turbo. I did see almost 245f oil temps near the top of the grade but when the clutch engaged it would pull temps down-but the darn thing would only stay locked a short time and not bring the temps down enough for me. I'll have to pull the fan clutch and adjust the spring before the next trip. I picked up a fan for the oil cooler and ordered a temperature switch to activate it. Without the engine fan pulling air through the oil cooler it's hard for any cooler to keep up. I chose not to run the engine oil through the radiator cooler so cooling the oil is strictly up to the air passing by now. The fan should make a significant difference I hope.
Glad we got to meet and thanks for the kind words.
Hal

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Re: Diesel review [message #296901 is a reply to message #296899]

Mon, 07 March 2016 18:04

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

Hal,

I kind of figured you would be able to pull those grades a lot better with that inter-cooled, turbo charged, diesel than I can with an old 455 gas engine. I'm sure, once you get the cooling bugs worked out nothing will slow you down.

Hope to see more of you and Bianca. Maybe you can make a GMCSJ rally sometime, although we don't normally have any of them very close to Albuquerque.

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Re: Diesel review [message #296904 is a reply to message #296877]

Mon, 07 March 2016 19:30

Chr$

Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ

Karma: 1

Senior Member

Well, that engine gets 13-14 in a pickup truck, so I wouldn't be surprised at 13MPG... Beats the 9MPG I get with my 4.6 pulling a 3 ton trailer... Rolling Eyes

-Chr$: Perpetual SmartAss
Scottsdale, AZ

77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"

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Re: Diesel review [message #296908 is a reply to message #296890]

Mon, 07 March 2016 20:36

Neal Krisher

Messages: 54
Registered: November 2013
Location: Apple Valley, MN

Karma: 0

Member

Thanks for sharing Hal. Interesting project for sure.

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Re: Diesel review [message #296913 is a reply to message #296877]

Mon, 07 March 2016 22:03

Ed K

Messages: 14
Registered: February 2014
Location: Northern Illinois

Karma: 0

Junior Member

Hal you indicate your trans drops out of overdrive, what trans are you using behind the 6.5 diesel?

Illinois

76 Palm Beach 74 Corvette 08 Jeep Liberty 02 Honda Silverwing

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Re: Diesel review [message #296916 is a reply to message #296913]

Mon, 07 March 2016 23:10

Hal StClair

Messages: 971
Registered: March 2013
Location: Rio Rancho NM

Karma: -12

Senior Member

Ed K wrote on Mon, 07 March 2016 21:03

Hal you indicate your trans drops out of overdrive, what trans are you using behind the 6.5 diesel?

Illinois

It's a 4l80e, basically a TH400 with an overdrive. It's also an electronically operated trans that is PCM shifted so is optimized to work well with the motor. Nice tough trans.
Hal

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Re: Diesel review [message #296924 is a reply to message #296916]

Tue, 08 March 2016 06:47

dr.diesel

Messages: 85
Registered: April 2015
Location: The Haute, Indiana

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Member

Hal StClair wrote on Tue, 08 March 2016 00:10

It's a 4l80e

I didn't realize they made a transverse 4L80E, or did you accomplish the swap some other way?

Very Nice though. :thumbsup:

77 Kingsley

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Re: Diesel review [message #296926 is a reply to message #296924]

Tue, 08 March 2016 07:09

Neal Krisher

Messages: 54
Registered: November 2013
Location: Apple Valley, MN

Karma: 0

Member

dr.diesel wrote on Tue, 08 March 2016 06:47

Hal StClair wrote on Tue, 08 March 2016 00:10

It's a 4l80e

I didn't realize they made a transverse 4L80E, or did you accomplish the swap some other way?

Very Nice though. :thumbsup:

Hal built an alternative solution ... http://www.gmcmhphotos.com/photos/member-galleries/p57371-progress.html

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Re: Diesel review [message #296930 is a reply to message #296877]

Tue, 08 March 2016 08:19

gbarrow2

Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...

Karma: 3

Senior Member

Hal,
Congrats on completing a very complicated project.
You didn't state which final drive gear you used. I have a 2:73 out of a low mileage Eldorado that I don't need. Would that work for you?

It is in Southern California. Surely there will be a GMC'er going your way who can transport it.

Email or PM me if you have any interest.

Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach

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Re: Diesel review [message #296948 is a reply to message #296930]

Tue, 08 March 2016 12:00

Hal StClair

Messages: 971
Registered: March 2013
Location: Rio Rancho NM

Karma: -12

Senior Member

gbarrow wrote on Tue, 08 March 2016 07:19

Hal,
Congrats on completing a very complicated project.
You didn't state which final drive gear you used. I have a 2:73 out of a low mileage Eldorado that I don't need. Would that work for you?

It is in Southern California. Surely there will be a GMC'er going your way who can transport it.

Email or PM me if you have any interest.

Thank you very much for the offer but I'm afraid it wouldn't work in my application. The differential I used was the front axle from a 2011 up Chevy/GMC HD 3/4 or 1 ton truck. The ratio I used is a 3.73 but when taking into account the transfer case 1.1 to 1 ratio and .75 OD in the trans it works out to a 3.07. Plus using a slightly taller 215x85x16 tire brings it down a little more. A 3.42 was available but I'm not sure it's worth the effort/expense to change or if I'd be happy towing with it.
Some one doing a diesel swap should be interested in your FD though.
Thanks again,
Hal.

[Updated on: Tue, 08 March 2016 12:06]

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