1991 Cummins Suburban

[Spur]

My plan was to use a dual Flex fan setup but ditch all the wiring and thermostats that come with it and replace with better. Most of the problems I've heard about are with the wiring, not the fans themselves.

Suppose I could try to find an OEM fan, but it sounds like a lot of hassle and I wouldnt know where to start.

I'll have to get back to you on the specs of the radiator. Tired. Gotta get up at 5 AM.

 

[bftank]

your coolant temps are just fine, 200 degrees is where a diesel is most efficient.

 

[Spur]

your coolant temps are just fine, 200 degrees is where a diesel is most efficient.

Good to know. I thought it might be fine but the odd smell was/is worrisome. Been busy with work for the last couple days. Hopefully I'll get a chance to do some work on the truck this weekend.

My buddy and I are planning a trip to the Canyonlands in August and there are a lot of things I'd like to do before then. Hopefully I'll get some of the following done before then.

1. Troubleshoot malfunctioning winch solenoids.
2. Find out where the burning plastic smell is coming from.
3. Figure out what I'm going to do about the fan.
4. new Alcan rear leaf springs (yeah!)
5. Replace the terrible vinyl flooring (most regretted decision of the build)
6. Maybe, finally find the time to start on the rear storage drawers
7. Redo the battery tray to accommodate duals and move the big Die Hard Marine to the rear house battery and install the National Luna dual battery kit that's been sitting in a box for a year.
8. Install the water system that has also been sitting in a box for the last year.

Plus a million other little things...

 

[chew246214]

I know this thread has been going on for a long time and hasn't been touched in a while.. I just found it..... great build.... I went through every page but failed to notice.... if you don't mind me asking how much do you have into this build so far? I know it was more then the expected $10000 you mentioned, but how much more? Thinking of going a similar route and would love real world numbers... thanks

 

[Czechsix]

I'd be interested too. I'll throw my numbers out to you via pm

 

[ExpoMike]

Just reading over the last few things about the temps. 205 is not bad as many vehicles are designed to run at 210 for emission purposes.

You're biggest issue is not having a fan shroud. This helps the fan pull air through the radiator versus just spinning air around. Every person I have seen with overheating issues (assuming the engine is tuned correctly) in older vehicles has been a lack of a fan shroud. Once they installed one, temps dropped way down (like 20-30*). Also having the correct clearance from the radiator and the fan blades sticking about 1/2" behind the back edge of the shroud. Fans and shrouds are kind of a sience to get proper air movement.

Good luck on your build.

 

[BCHauler]

I'm sure you've solved the fan issue by now, but I too will put in my vote for the fan shroud. I've done some motor swaps in my time and the shroud makes a big difference. Some tricks are to get a stock shroud and trim it back to the mounting frame and then build on a custom shroud with aluminum.

 

[Spur]

It's going back into the shop next week to get a few things taken care of. I'm going to ask them about a custom fan shroud.

New Alcan springs are going on the rear. Single battery is getting changed over to duals and the big Marine Die Hard Platinum will become the house battery.

If anyone is interested in the numbers, I'll PM you.

 

[JB-weld]

Wow, this is an EPIC thread! I just sat and read through the whole thing. Nice job on the build Spur, and thanks for posting up the details. Sharing your experiences makes it a lot easier for others looking to do the same mods. I have a '90 2500 Burb with a tired 350, and recently picked up a running 92' Dodge W250 Cummins truck for the drivetrain. I'll be collecting more parts and rebuilding axles for a couple more months before I start the swap, probably this fall.

You've listed a couple things you're planning on changing, like your fan/shroud issue, and the vinyl flooring. Is there anything else about the build you would do differently?

I'll probably have more questions for you down the road if you don't mind.

-JB

(Edit: I've lurked here for over a year, and this is my first post......sad.)

 

[Spur]

Wow, this is an EPIC thread! I just sat and read through the whole thing. Nice job on the build Spur, and thanks for posting up the details. Sharing your experiences makes it a lot easier for others looking to do the same mods. I have a '90 2500 Burb with a tired 350, and recently picked up a running 92' Dodge W250 Cummins truck for the drivetrain. I'll be collecting more parts and rebuilding axles for a couple more months before I start the swap, probably this fall.

You've listed a couple things you're planning on changing, like your fan/shroud issue, and the vinyl flooring. Is there anything else about the build you would do differently?

I'll probably have more questions for you down the road if you don't mind.

-JB

(Edit: I've lurked here for over a year, and this is my first post......sad.)

Good luck with the build. Happy to help with any questions. Don't forget 4bt swaps and TN Diesel for good resources. I'll try to share some of my regrets and issues that I ran into.

1. Insulate the firewall. Should have done this while the engine was pulled. The Cummins produces a lot of heat and you'll notice it in the cab. Not a bad thing in the winter but an issue in the summer.

2. Box the frame from the beginning. Didn't realize this had to be done until the engine was back in.

3. Plan on a steering stabilizer from the beginning. It helps.

4. Suspension. This is a logistical issue that is a pain. The truck needs custom springs to support the weight, but you need a final weight in order to get them made. Also, you need a 4" lift to put the Cummins into the Suburban. So I bought a Tuff Country lift kit and cheapo generic shocks in the beginning. Once everything was done, I weighed it and had the springs made. Then the old stuff was sold for pennies on the dollar. Maybe you can figure out a better way to do this. Also, very disappointed with National. Terrible customer service, 2 weeks late, sent the wrong hardware and the springs are about 2" higher than what I specified. Going with Alcan for the rears.

5. The NV4500 is a stout transmission but it's a mushbox compared to a ZF5 or ZF6. Wish I would have listened to Andre's advice from the beginning. See post #22 If I ever blow up the NV4500, I'll replace it with a ZF.

6. Wish I would have spent a little more money and put an ARB in the rear instead of a Detroit. I've got so much torque that it's easy to lockup the Detroit. It hasn't caused any major disasters yet, but I have to be really careful, especially in wet and winter conditions. It's an upgrade that I'm sure I'll do at some point.

7. Wish I had a ladder on the rear swing-out. It's tough getting up to the roof rack, even before I got the 37s.

8. I got a 12k Warn winch used that was essentially brand new. It was a good price, so I bought it. I was worried from the beginning that it might be a little under-powered. It struggles a little bit. It works fine but a 15k winch would have been more appropriate.

Hope that helps.

 

[bfdiesel]

Get a snatch block and the 12k becomes 24k. I have an old 8274 and snatch block that could pull my 2004 sierra 2500hd duramax out unless it was completely buried in ice capped snow, I did however pull the 10" power poll post up out of the frozen ground.

 

[Spur]

Get a snatch block and the 12k becomes 24k. I have an old 8274 and snatch block that could pull my 2004 sierra 2500hd duramax out unless it was completely buried in ice capped snow, I did however pull the 10" power poll post up out of the frozen ground.

Oh yes, I have a good snatch block. It helps a lot.

 

[JB-weld]

Hope that helps.

Absolutely, Thanks!

Good luck with the build. Happy to help with any questions. Don't forget 4bt swaps and TN Diesel for good resources. I'll try to share some of my regrets and issues that I ran into.

1. Insulate the firewall. Should have done this while the engine was pulled. The Cummins produces a lot of heat and you'll notice it in the cab. Not a bad thing in the winter but an issue in the summer.

I was already planning on insulating both sides of the firewall for noise, but I hadn't really thought about heat.

2. Box the frame from the beginning. Didn't realize this had to be done until the engine was back in.

I'll be boxing the frame all the way back to at least the front hanger for the rear springs.

3. Plan on a steering stabilizer from the beginning. It helps.
4. Suspension. This is a logistical issue that is a pain. The truck needs custom springs to support the weight, but you need a final weight in order to get them made. Also, you need a 4" lift to put the Cummins into the Suburban. So I bought a Tuff Country lift kit and cheapo generic shocks in the beginning. Once everything was done, I weighed it and had the springs made. Then the old stuff was sold for pennies on the dollar. Maybe you can figure out a better way to do this. Also, very disappointed with National. Terrible customer service, 2 weeks late, sent the wrong hardware and the springs are about 2" higher than what I specified. Going with Alcan for the rears.

I already have a 4" TC lift on the Burb now, but I was thinking about getting some second or third gen Cummins coil springs and linking the front axle. Not really for more flex for wheeling, but to get the right spring rate and a decent road ride.

5. The NV4500 is a stout transmission but it's a mushbox compared to a ZF5 or ZF6. Wish I would have listened to Andre's advice from the beginning. See post #22 If I ever blow up the NV4500, I'll replace it with a ZF.

I already picked up a late model NV4500 (the donor truck is an auto), and liked the NV that I had in a previous truck, but I'll definitely check out the ZF before I put any money into it.

6. Wish I would have spent a little more money and put an ARB in the rear instead of a Detroit. I've got so much torque that it's easy to lockup the Detroit. It hasn't caused any major disasters yet, but I have to be really careful, especially in wet and winter conditions. It's an upgrade that I'm sure I'll do at some point.

Good to know. I have the Dana 70 out of the donor truck with an open diff, but I was considering a 14 bolt that I also have, because it bolts in, and Detroit's are relatively cheap for them. Maybe I'll reconsider that, and stick with the 70 for now.

Thanks Spur!

 

[Czechsix]

I'll second the insulation idea - and while you're at it, do the rest of the truck too.
My frame is boxed to a bit behind the front spring rear mount, seems to be working fine.
Make sure you tie the boxing into the steering box to reinforce that area, common crack area.
At this time my truck has a 6" front lift from National, and that's as high as it's going to go. Still has the rear springs from Superlift, but eventually those will go away too, in favor of Nationals. I haven't had an issue with National, but that's because I live close to them, and when I had my springs made I was right there all through it. Every vehicle is different, and they had the springs on and off three times before they were happy with it. I think one of the major issues with doing something like that remotely is every vehicle is different and it's impossible to get perfect results without having the truck there. They can get only so close. But if I were you, I'd check into local spring shops. It's just leaf springs, not rocket science, and if you'd like I can show you what my front springs look like to give you a better idea as to leaf count, wraps, etc.
I've got the NV4500, works OK, would like another gear though, hehe. But it works, and I have no plans to replace it.
Regarding the torque lockup on the Detroit, you can get used to it. Just has different mannerisms, but I agree that something selectable would be ideal. I have front and rear detroits, but I don't live in an area that's got snow, my traction issues are all off road ones.

 

[Spur]

Sounds like you've got a good plan. I'll be very interested to see what you come up with for the front suspension.

Keep in mind that I found the TC rear springs to be inadequate as well. With the Suburban loaded with gear or towing even a small trailer, they were not stiff enough. My rear axle weight is about 4700 lbs when I've got it loaded with gear. I don't think the TC springs were designed for that.