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Quadrasteer 8.1L Suburban tow rig

2003 Suburban 2500 Quadrasteer camper towing 8.1L 6.0L swap 4L80-E

Blue85

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Blue85 submitted a new Build:

Quadrasteer Suburban tow rig

Having really liked our 2005 Yukon XL, I was gearing up to tow a small-ish camper across the country with it (5.3L 4x4 3.42 gears, Autoride). At some point I decided that a 1500 with soft coil springs and tall gears might be OK for camping a few hours from home (I even got the airbag shocks and compressor working again), but for thousands of miles and tackling the continental divide, a stouter rig was in order. No interest in pickups since they're too cramped for 6 people all day long. While looking for 3/4-ton Suburbans I remembered that some Quadrasteer ones had been built. Since I was involved a little with the truck 4-wheel steering during my time at Delphi (see https://patents.google.com/patent/WO2001020822A1/zh), I decided no other vehicle would do. So after chasing them down in various parts of the country, I ended up driving to Syracuse to pick up this Maryland native.

(pics to follow)

Read more about this build here...
 

Blue85

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After tackling a little maintenance like broken manifold bolts, intake gaskets, a failed belt tensioner and wonky MAF sensor, it was working great. So we had 1 night in our camper (since buying it) and a 1.5-hour tow in each direction before setting out on our first epic road trip. There is a thread about it with cool trip pictures: https://ck5.com/forums/threads/how-warm-should-my-engine-get.330868/. Basically everything worked great except I had to replace the fan clutch.

2017 summer road trip.png
 

Blue85

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"So where is the build?"

The 4L80-E will let you tow in OD in tow/haul mode, but it will drop out of 4th gear even on level stretches, especially if there's any kind of wind. So that meant 6000 miles of working the throttle manually. Possibly some tweaking with HP tuners would improve this situation, but I'm leaning more towards a brute force method - i.e. big block torque. Sure, the 6.0 makes 325HP, but it's screaming when it does. Would love to tackle the grades in 3rd gear instead of 2nd and not be screwed if I have to drop some momentum in traffic. Climbing mile after mile over 4500 RPM gets unnerving.

So what years 8.1L should I look for? Everything I'm seeing on Car-part.com now is like $2k, at which point I might as well buy a donor vehicle. I found an '02 Avalanche a few hours away for $1500, for example. It looks like 2003 was the last year for return-style fuel rails. It would be nice to keep the existing fuel system vs swap the fuel pump module (and maybe the lines?). Although it's a dual-tank setup, I'm not sure returnless has any impact on the the aux pump.

I've heard you can use the 6.0 PCM and just change the fuel map, but I prefer a whole 2nd PCM/harness setup just in case the 6.0 tries to find it's way into the K5 :whistle:. If I grab just an engine, I'll grab the exhaust manifolds, intake setup, maybe motor mounts. Is the radiator different?
 

beags86

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I don't know for sure, but it seems that the 8.1 didn't come in the quadrasteer. I wonder if there is a reason for that?
If I recall correctly that's a Dana 60 rear, you should be fine. But maybe something to think about?:dunno:
 

Blue85

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Correct, all 2500 Quadrasteers got the 6.0. There was also a 6-lug version of the same D60 axle for 1500, but I don't think that ever went in the SUVs. If there's a weak link it's probably the half-shafts but there are few reports of them ever failing. I've seen Dura-burbs made from Q-steer trucks. Just because there are no reports of them failing doesn't really imply robustness on such a rare case, though.

For most towing conditions, the torque through the differential is the same as with SBC, I've just slowed down the engine. I suppose having more engine I can push harder up hills which puts more heat in the diff. Maybe just switching to synthetic gear lube will be enough. 1st gear launches could be abusive, but that's not really what this truck is for...
 

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Always thought the quadrasteer option was a trick setup. Too bad gm screwed the pooch when it came to the marketing and sales of it to pull the plug due to lack of sales.

As far as the 8.1 is you are right the fuel system went returnless in '04. Early 8.1's did have the issue with the crank sensor that should be upgraded to the later one to prevent failures.

The intake are similar and you could swap to the older return style fuel system if you could only find a later engine.

ECM should be the same 0411 that the LS uses. I'd suggest you dive down the rabbit hole that is the 8.1 swap thread as Larry has all the details in there.

The other option is to regear the diffs but that's still going to keep the 6.0 spinning fast. It will at least be more in its power band though.
 

Blue85

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When I did math on the highway it came out to 4.10 gears, but the RPO sticker says 3.73. I do need to rebuild the POWR-LOCK, but turning the driveshaft should be easy enough to verify. If I was regearing lower I would want to go bigger than the crazy short 245/75R16's
 

beags86

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Always thought the quadrasteer option was a trick setup. Too bad gm screwed the pooch when it came to the marketing and sales of it to pull the plug due to lack of sales.

As far as the 8.1 is you are right the fuel system went returnless in '04. Early 8.1's did have the issue with the crank sensor that should be upgraded to the later one to prevent failures.

The intake are similar and you could swap to the older return style fuel system if you could only find a later engine.

ECM should be the same 0411 that the LS uses. I'd suggest you dive down the rabbit hole that is the 8.1 swap thread as Larry has all the details in there.

The other option is to regear the diffs but that's still going to keep the 6.0 spinning fast. It will at least be more in its power band though.


What are you talking about?

Did you not see the look on this cows face?

Lol! I actually think it had to do more with the pricing more then marketing. It was the quadrasteer option was 5700 extra meaning that a fully loaded half ton crew cab pickup was priced around 44k
Sure that's actually laughable in 2020, but in 2003 that was way to much dinero for the avg person to shell out.
Marketing. Sure gm flat out sucks at paying for marketing. Chevy SS. Great car with no market because they didn't advertise it, Camaro Dead last in sales in the pony car wars because they don't advertise it. Meanwhile you can't watch 10 minutes of tv with seeing some form of a FCA commercial.
Also we have to see that same bearded tool talk to a "focus" group about what boring suv won some award we don't care about. Anyway....
GMs price greed more than anything killed the quadrasteer.
Rant off.
Oh yeah, ford is come out with a 4 wheel steer pick up in the next couple years. Possibly even a dually.

Is the quadrasteer that important to you? What about just buying a 8.1 burb?
 

ZooMad75

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I honestly can't remember seeing an ad on TV or in any car/truck magazine for a quadrasteer burb. I was at gm when it first came out on the Sierra c3 (it was not called a Denali even though it had the same facia and trim as a Denali Yukon, the GMC guys got pissed if you called it a Denali pickup) They advertised that like crazy because GMC wanted something to differ them from Chevy. I was still there at the start of the 2003 model year and dealing in order management for fleet and the Chevy offering of the quadrasteer was a surprise to all of us in my department.

I agree they didn't help with pricing at all. That was a steep cost for the option. But as they still do today they don't do much advertising on the Suburban. So if you don't put out ads for the burb you can't boast about the quadrasteer.
 

Blue85

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The pricing did improve as years went on and you were able to get it without every single luxury feature. Don't think any ads, posters or much of anything talked about the XL/Sub which is why they're even more rare. In those years Delphi was under exclusive contract with GM, but we had prototypes on Ram and Nissan. Those could have happened, along with the narrower gen 2 Q-steer, if the low sales hadn't scrapped the whole project. So we ripped out the assembly line and built my EMC lab there. It was a site separate from the main Saginaw complex.
 

Blue85

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Is the quadrasteer that important to you? What about just buying a 8.1 burb?
Fair question that somebody has to ask. I did explain a bit in the introduction post, but not everyone reads those. I have also compared A/B pulling firewood with the XL and the Q-burb and there are places I just can't put the trailer with the 2WS. The towing/ in-phase mode is cool on the highway but I don't think that sells the system by itself. On the other hand, it's dead awesome in parking lots and I can even turn around on smaller roads. It's basically turning radius like a sedan.
 

beags86

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Fair question that somebody has to ask. I did explain a bit in the introduction post, but not everyone reads those. I have also compared A/B pulling firewood with the XL and the Q-burb and there are places I just can't put the trailer with the 2WS. The towing/ in-phase mode is cool on the highway but I don't think that sells the system by itself. On the other hand, it's dead awesome in parking lots and I can even turn around on smaller roads. It's basically turning radius like a sedan.
I did read it. But I guess I didn't make the connection that the sentimental reason of the steering was worth more the stress of over rev'ing a 6.0 on a mountain pass.
I do remember you looking for that burb.
Of course I've been looking for an non overpriced clean 8.1 burb for 3-4 months now. So it's not like those grow on trees either.
You can find them all day. But they are hashed. A clean one is still 12-13k and even those are likely to have 175k+ miles on them.
So maybe you are better off with the swap. I would be lieing to say I haven't thought of swapping a clean 6.0 burb myself.
 

Blue85

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Going into to it I thought the 6.0 would be ideal. There are posts all over the internet about how great they tow, our camper isn't huge and I hoped to get decent mileage for non-towing stuff. Plus the 8.1 gets bad-mouthed for not making much more HP, so just put a cam and headers on the 6.0, blah, blah. That's probably a good plan for a DD and stoplight racing, but to me the really enlightening testimonials are those who have towed with both engines. Also, a lot of towing talk people only talk about weight. In truth a camper has way more wind drag than a car on a trailer. A supercharger sounds nice but you could buy a whole tow rig for the price of one. Any fuel savings would likely be consumed by buying premium gas and now you have to keep an eye on knock as the temperature climbs and issues will cost you the engine.

I've tried to research what improvements can be made with a tuner, particularly the lock/unlock and shift points with load. There are also stories of lots of power left on the table (for example, some say stock calibration requires 60 seconds of WOT before activating performance enrichment). But I'm yet to find a single story where somebody said the towing was marginal and gear hunting an issue, then after tuning they were happy with it.
 

Scribbles

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What are you talking about?

Did you not see the look on this cows face?

Lol! I actually think it had to do more with the pricing more then marketing. It was the quadrasteer option was 5700 extra meaning that a fully loaded half ton crew cab pickup was priced around 44k
Sure that's actually laughable in 2020, but in 2003 that was way to much dinero for the avg person to shell out.
Marketing. Sure gm flat out sucks at paying for marketing. Chevy SS. Great car with no market because they didn't advertise it, Camaro Dead last in sales in the pony car wars because they don't advertise it. Meanwhile you can't watch 10 minutes of tv with seeing some form of a FCA commercial.
Also we have to see that same bearded tool talk to a "focus" group about what boring suv won some award we don't care about. Anyway....
GMs price greed more than anything killed the quadrasteer.
Rant off.
Oh yeah, ford is come out with a 4 wheel steer pick up in the next couple years. Possibly even a dually.

Is the quadrasteer that important to you? What about just buying a 8.1 burb?

I remember that commercial quite well, my brother and I tried very hard to get my Dad to buy a Quadrasteer burb back then just because of these commercials but my parents (Mom) cheaped out! :rotfl:
 

Blue85

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Junkyards are getting like $2k, which seems to be about where I could score a whole vehicle. Obviously nice to hear it run.
 

Chevy305

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The factory tuning is pretty lame on both engines. Power enrichment doesn't come in until over 90% throttle and over 5000 rpm for 60 seconds or so. I tuned my '00 5.3 Tahoe and it really woke it up. Regardless of which engine you go with, get HP Tuners and just make some minor tweaks.

This is a good explanation of how PE works.

 
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