1991 Cummins Suburban

[Metcalf]

Rerouting the exhaust would suck, but my exhaust ( and up to 4" ) fits between the np205 and the frame with a passenger drop axle. Seeing that the GM frame is really similar I would think it would work.

The old JB conversion lo-max, 205 based, transfer case with the 3:1 low range would be ultimate. I don't think they sell it anymore though. They only offered like 2 input splines and neither of them worked for the dodge diesel

Another interesting option would be a np205 with a NWF 2.72 planetary reduction box in front of it. I don't really think you need a doubler with the diesel for 99% of what the truck would do....but it would be slick. On the dodge the doubler gets rid of the factory wierd figure-8 to round adapter with its 29-spline male coupler setup....

I still want a 6-speed in my truck :coffeedrink:

 

[Spur]

Rerouting the exhaust would suck, but my exhaust ( and up to 4" ) fits between the np205 and the frame with a passenger drop axle. Seeing that the GM frame is really similar I would think it would work.

The old JB conversion lo-max, 205 based, transfer case with the 3:1 low range would be ultimate. I don't think they sell it anymore though. They only offered like 2 input splines and neither of them worked for the dodge diesel

Another interesting option would be a np205 with a NWF 2.72 planetary reduction box in front of it. I don't really think you need a doubler with the diesel for 99% of what the truck would do....but it would be slick. On the dodge the doubler gets rid of the factory wierd figure-8 to round adapter with its 29-spline male coupler setup....

I still want a 6-speed in my truck :coffeedrink:

Agreed. Both of those options would be slick. But like you said, not really needed. I've got plenty of low end torque. I would rarely use a twin-stick. Not like I'm going to be rock-crawling in the burb.

On a related note, I recently got to play around with a truck that had a zf5. Made me kind of jealous. At the very beginning of this thread someone recommended that I look into it, but I never really considered it. I regret that now. The zf5 makes my nv4500 feel like a mushbox. It's so much crisper and easier to shift.

 

[MrBeast]

I was sitting here stressing out over my transfer case setup, I have a figure 8 205, I was wanting to mount it to my NV4500, but the adapter costs about 550.00, but it just so happens that I just so happen to have a NP203, and a Doubler kit costs about 599.00 from north west fab. So that is probably the route im going. I am not planning on doing any rock crawling, but there will be times I climb steep hills pulling a trailer, and times I am backing that trailer up the hill where a good solid low range would be nice. So I am considering it.

I also happen to have a NP241 out of a 90 burban sitting here. But I really dont want a chain driven transfer case.

Id love to get an atlas, but dont really want to shell out the money for one.

 

[huntsonora]

Yeah. Since I have that massive Kenworth 200 amp alternator, I imagine if the regulator isn't working properly it could fry things pretty quick. On the upside I won't have any trouble charging up multiple batteries!

Funny you mentioned that. I was just thinking last week that we are pretty close and we should meet up when the chance presents itself. I'm in Crested Butte. If you're ever passing through Gunnison, definitely give me a shout.

I spend a lot of time around Crested Butte in the summer scouting for the upcoming hunting season. You going to be around there this summer?

 

[Spur]

I spend a lot of time around Crested Butte in the summer scouting for the upcoming hunting season. You going to be around there this summer?

I will. Shoot me a pm when you're up my way.

 

[Spur]

I was sitting here stressing out over my transfer case setup, I have a figure 8 205, I was wanting to mount it to my NV4500, but the adapter costs about 550.00, but it just so happens that I just so happen to have a NP203, and a Doubler kit costs about 599.00 from north west fab. So that is probably the route im going. I am not planning on doing any rock crawling, but there will be times I climb steep hills pulling a trailer, and times I am backing that trailer up the hill where a good solid low range would be nice. So I am considering it.

I also happen to have a NP241 out of a 90 burban sitting here. But I really dont want a chain driven transfer case.

Id love to get an atlas, but dont really want to shell out the money for one.

I think any of those options would be great. Only you know what you need, but I'm wondering if you would really use the extra low range. Just consider that the 241 is really a great t-case. People rightly assume that gears are stronger than chains, but it's really hard to break a chain. Most failures involve leaking gaskets and it can be rebuilt very simply. They sell the rebuild kits for about $200

That being said, twin stick it! It would be awesome!

 

[Spur]

Picked up my new battery this morning. So impressed with Sears customer service. They really went above and beyond in my mind, drivin 250 miles round trip to pick up a battery from another store. The girl at the counter said she didn't get home till 10 PM, but chuckled and said she was happy to do it.

Hooked it up and the multimeter read 14.5 to 14.6 depending on how much I revved it. Seems pretty stable, but I'm going to get it checked out anyway just to be sure.

Planning on going to duals and using the marine for the house battery, but it will require some re-wiring and a new battery tray. I think I've got room, but two P-4 Die Hard Plats will be a very tight fit.

 

[MrBeast]

Nice!

Will be waiting to see how you make it all fit.

I was planning on putting both of my batts on one side so as that I could run a air filter box on the passenger side, but since I am going to go with a vintage air setup I am going to bring my induction air through the old blower motor hole off the cowl.

 

[Spur]

Finally got around to calculating my mpg. I had the back completely loaded with gear. Stopped at a truck stop and weighed in at 8300 lbs. Over about 400 highway miles I averaged 19 mpg. That includes a lot of steep mountain passes. I was hoping for 18-20 so I'm really happy about that. With an unloaded vehicle, I bet I could do better than 20 mpg.

 

[Metcalf]

What was your speed? Tire pressure? RPM? Boost?

When I drop my truck down to about 60mph the mileage goes WAY up.

 

[Spur]

Tire pressure is 55
I never drive faster than 65
Boost is about 10 at 65 and rpm's are about 1500.

The truck really likes to be at about 55-60. Above 65 the rpm's, water temp, and EGTs start to go up and it starts to vibrate a bit.

 

[Metcalf]

Slow down till boost is at or under 3psi. Depending on the turbo and fuel settings this might be like 50 or less. Mileage should go WAY up. Its fun to find the sweet spot and get like 25+ mpg, even if its just for a bit....

You might also try backing off the screw on the top of the AFC that pre-sets the position of the fuel pin. That can reduce cruising fuel. Its free to try.

Also, you could adjust the AFC starwheel spring to have a little more preload. This might reduce your cruising boost a bit and keeping fuel use down.

I think the pump tuning is more of an art than a science Its all free and easy to try, just keep track of what you changed.....

 

[lstzephyr]

I drove my truck around for awhile with a major boost leak and got used to driving at 65 with no boost. Now I rarely have more than 2-3 psi on the highway, usually its no boost. I get about 23-25 mpg if its just highway, 20ish mixed.

I would back off a bit so you aren't pushing so much boost.

 

[Czechsix]

Dang, much better than the 24v I have. I weigh more (how'd you get that weight so low?), have bigger tires and more lift though. All of which kill mileage.

What really kills mileage is some turd stole the alternator, not going anywhere until that gets replaced or upgraded.

 

[Metcalf]

Shoot, my truck is still under 8K. Even with the big tires and camper shell its about 7000-7500 or so. Not that 7K is THAT light, but its all relative. I think the weight when the truck was new at the DMV ( stupid Colorado ) was listed at 6500lbs.