[Other] Starting vehicle platform

[GMCJason]

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Ok guys, we need some more action in this forum so let's discuss something that I've been thinking about lately, namely the platform on which to start a build. I don't know how serious I am but this is something that I can't overlook.

Here's the scenario. I have a 1990 3/4 ton Suburban and ultimately want to end up with a full 1-ton version. For those of you that aren't familiar with them it's got a TBI 350, a TH400, NP 241 t-case and a semi floating 14 bolt in the rear and a 10 bolt up front.

What I want is a Sub with a fuel injected big block, a 4L80e tranny, not so worried about the t-case so the 241 would probably work but I'm flexible there, a full floating 14 bolt in the rear and a Dana 60 up front. Now, I could use the '90 as a starting point but I'd be swapping out just about every component in the drive train, including the engine.

Another option would be to start with a later model Suburban. If I went to 1991 I could get a stock 4L80e but otherwise it's the same as what I have now. If I went slightly newer yet I could get a 3/4 ton with a 454, 4L80e and a 14BFF already installed. I would then swap the front axle/suspension system with a Dana 60 and deal with the t-case accordingly.

I've been researching some of the costs lately and I don't think that the SAS on the newer truck would be that much different than what I have planned now. The solid axle conversion kit from somebody like Off Road Unlimited is a bit pricey at about $900 but after that I'm pretty much where I am now. New front springs are already part of the plan and so is the axle. Cross-over steering is required with the new solid axle but I wanted to do that anyway. I know that I'd have to change the transfer case out since I have a GM Dana 60 but I already have a NP205 that I think would work or I'd just find a 241 for this app. The drive shaft length would have to be addressed anyway.

With the 90 I'd have to find a 4L80e transmission, controller, and get it installed with the necessary drive shaft modifications. There would also be the issue of the engine...

So, what do you guys think? I'm interested in some other thoughts.

[38377k5]

I would vote for the '90. I like the body style much better. Plus, who knows what shape the 454/4L80E are in if you get a newer one.

[MrK5]

I'd start with the newer 454 equipped Burb, but I don't know a lot about them. I've thought about doing something similar with a mid-90s Tahoe.

Actually, I'd look for a 6.5L TD equipped model. I think the '95 would be the better option, I seem to recall something changed in the 6.5L's to improve them about that time.

What would you be using the truck for? Is the 454 really that necessary? I guess the only value I see is the wow factor. I figure we stress things enough with tires, lockers, and low gears that a big block is just amplifies it all that much more. That's my other arguement for a 6.5L

The other thing I'm just generally curious about, how much difference does the 4l80e make in fuel mileage versus a TH400?

[GMCJason]

Originally Posted by 38377k5

I would vote for the '90. I like the body style much better. Plus, who knows what shape the 454/4L80E are in if you get a newer one.

That is a good point. It is likely that a rebuild would be in order for each so the only benefits gained would be a) the parts don't need to be acquired, and b) they are already part of a working system.

I do like the body style and I also like the fact that it's not quite a complex as the newer ones.

Thanks for your input Chris.

[5280k5]

I have to ask but is a 5 speed completely out of the question? Yeah, I know more work but low gear & overdrive is a nice combo

Anyway, back to your question. It sounds like to me that you're already leaning towards the idea of a newer burb with a SAS and if that's the case I would seriously consider going to a '96 & newer Vortec 7.4l. Yes, they still cost more, but having driven a lot of these & the older TBI trucks if you can swing the $$ the MPFI Vortec's shame the older big blocks.
The nice thing about any of the big block trucks is a lot of the owner's are willing to part with them for less than usual due to our rising costs of fuel.
The tranny guy at my old shop I think still has a newer style 8.1l floating around and he could whip you up a 4l80 and you're all set to go

[cbbr]

I am working (slowly) on swaping the axles on my '90 3/4 Burb to a 60/14bff. Crossover, a panhard setup and 4 wheel discs are part of this phase.

The TH400 is fine with me. I will be swapping other stuff (driveshafts, yokes, etc.) until the engine blows, then I'm thinking about a 4BT. 1 ton and 20 MPG.

[GMCJason]

Originally Posted by MrK5

I'd start with the newer 454 equipped Burb, but I don't know a lot about them. I've thought about doing something similar with a mid-90s Tahoe.

Actually, I'd look for a 6.5L TD equipped model. I think the '95 would be the better option, I seem to recall something changed in the 6.5L's to improve them about that time.

What would you be using the truck for? Is the 454 really that necessary? I guess the only value I see is the wow factor. I figure we stress things enough with tires, lockers, and low gears that a big block is just amplifies it all that much more. That's my other arguement for a 6.5L

The other thing I'm just generally curious about, how much difference does the 4l80e make in fuel mileage versus a TH400?

What would I use the truck for...something I probably should have addressed earlier. I'm thinking championship rock racing. This would be sort of an all purpose vehicle. I want to be able to haul people and stuff, occasionally tow, cruise the highway at a decent RPM and be competent off road.

As for the question if the 454 really that necessary...Yep. I lean more toward the "too powerful is just enough". Is it overkill? Probably? Really necessary? Probably not. It's more of a toy. I don't think the 6.5L diesel would get me there.

I don't know how much difference there would be in fuel mileage with the 4L80e vs. the TH400 but that's only half my issue. The other half is engine RPM at cruising speed. I just don't like the idea of the engine spinning at 3000+ RPM, especially a big block. The mileage may not be that significant but there will be a difference. I haven't really checked the mileage in my '90 but we managed 13.5 MPG over the past week with the '01 and it's got the 8.1L with the 4L80e. It was mostly highway and combined a trip into the mountains and another into western Nebraska.

[GMCJason]

Originally Posted by 5280k5

I have to ask but is a 5 speed completely out of the question? Yeah, I know more work but low gear & overdrive is a nice combo

Anyway, back to your question. It sounds like to me that you're already leaning towards the idea of a newer burb with a SAS and if that's the case I would seriously consider going to a '96 & newer Vortec 7.4l. Yes, they still cost more, but having driven a lot of these & the older TBI trucks if you can swing the $$ the MPFI Vortec's shame the older big blocks.
The nice thing about any of the big block trucks is a lot of the owner's are willing to part with them for less than usual due to our rising costs of fuel.
The tranny guy at my old shop I think still has a newer style 8.1l floating around and he could whip you up a 4l80 and you're all set to go

For my purposes a 5 speed is not really what I want but it is a good thought. Maybe I should be more open minded.

I haven't really made up my mind, especially since I have the 90 and it would require changing. I'm just exploring options but it does seem to make a lot of sense when you look at it. If I went that way I would likely consider the '96 due to the Vortec engine. My only hesitation is that they are starting to get pretty complex and I want something I can tinker with. I know what you mean though, a while back I drove a 95 Sub with a supercharged 454 on 35's. I was not impressed and was a bit disappointed; could have been fun but it still wasn't enough to really move the beast. I'm pretty sure it had 4.10s.

Now, if I could score a 8.1L and 4L80e for my 90 I'd be thrilled, provided I had a GM tech that could help me get it all working. Any idea of how complete the setup is? Like does it have the wiring harness, accelerator pedal, computer, etc.? I may be interested in that.

[4x4dudester]

I would go with the later suburban, especially since you never see that many sas, and I think it would almost be the same amount of work.

[GMCJason]

Originally Posted by cbbr

I am working (slowly) on swaping the axles on my '90 3/4 Burb to a 60/14bff. Crossover, a panhard setup and 4 wheel discs are part of this phase.

The TH400 is fine with me. I will be swapping other stuff (driveshafts, yokes, etc.) until the engine blows, then I'm thinking about a 4BT. 1 ton and 20 MPG.

I've been watching what you are doing for obvious reasons I suppose. When you swap axles will you be running 4.56 gears with 37" tires? Do you think that highway RPM (about 2800 rpm @ 65 mph not accounting for the lack of lock up on the torque converter) will be OK with the diesel? Would be cool, though.

Thanks for the input guys.

[cbbr]

I haven't thought too much about it. There are a couple of local guys who run 4BT's in FSC's that I will be turning to for help.