Yet another Truck Questions Thread

There also is an overlooked down shift. The convertor clutch will disengaged first before an actual downshift is needed.

codrus wrote: Trucks got a lot more civilized during the 90s and 2000s. Being a '93, that one is likely to be less comfortable on long tows than the GMT800s referenced earlier. That may or may not be a significant factor to you. :)

Yeah I am sure that is true. I think most my towing would be less than 5 hours with most of it in the 2-3 hrs range not sure where that qualifies under long towing.

He said his newer truck rides better and gets better gas mileage but he's still not sure which he wants to keep.

I put the bug in his ear we see if it works out. Its a cool truck and part of me would like to keep it going just because its a one owner truck he bought new and in such good shape.

Ill snap a few more pictures if anyone is curious. Also depends on if he wants to sell and how much of a deal he would give me. If I could get a GMT800 with less miles for less than he wants then I would probably pass

Anyone know what some of this stuff is? Wilwood thing is down by the parking brake, is it a brake bias adjuster? Couple of the gauges almost looks like a boost pressure so maybe vacuum? And either air brake or air lockers or something?

Super clean interior no tears, headliner nice etc. He's not here or I would just ask

Air gauge is probably for helper air bags on the rear suspension. I also see the trailer brake controller, CB radio and Gear Vendors overdrive. Wilwood knob is a brake bias adjuster, although usually not inside the vehicle.

codrus wrote: I've never seen a 6.0 with the Allison, but I can't say it never happened. The 8.1 definitely had it as an option.

I see plenty of 6.0/Allison trucks but they are all 3500s.

In reply to iceracer:

In the test I did, at 60 mph in 3rd it was spinning 2600. In 4th, it was at 1800. 3rd made more noise, but performance was much better, no concern about the trans hunting between gears or getting hot because of a downshift to 3rd with the lockup clutch released and fuel consumption was almost exactly the same.

iceracer wrote: There also is an overlooked down shift. The convertor clutch will disengaged first before an actual downshift is needed.

Yes on some transmissions (others will unlock and downshift in one shot). And this is a seriously BAD thing when towing. You don't want the converter clutch unlocked any more than absolutely necessary with a heavy trailer back there. Even with a big trans cooler, an unlocked converter clutch under load on a steep hill leads to a E36 M3load of heat production.

Air gauge is for airbag helper springs. GVOD is worth big bucks. That is a sweet and beefy OD unit. That right there was a $3500 upgrade and will outlast the truck. The floor mount thing is obviously a tach. The thing beside the CB is a trailer brake controller.

Not sure why the brake prop valve is inside the truck, but that's what it is. Come to think of it, not sure why there is one at all. Makes me wonder what else has been hacked about the brakes.

rslifkin wrote: If the clutches are cooking themselves with fluid temps around 200*, then that trans is shifting way too soft and can't handle towing anything heavy regardless of temp. Crank up the line pressure or throw in a shift kit and that'll fix it. Plus, highway towing isn't generally when you'll cook a trans anyway, as it shouldn't be doing much shifting, so the clutch packs shouldn't be building up a lot of heat. Mind you, I did fry a converter lockup clutch in my 46RE the one time I let it into 3rd (and lockup) while beating the piss out of it on a track... Rest of the trans was (and still is) fine though, possibly due to being shift-kitted. Fluid temps were around 200* at the time. Lockup engagement was always pretty soft with the stock converter, so I knew that thing would give up eventually. A few turns on the line pressure screw and a better clutch in the new converter should resolve that problem.

This is exactly what I was talking about. They set shift pressures light to make them comfy which is not good for towing. And your TCC clutch frying while the fluid temps were 200 is also exactly what I was saying. You fried a clutch without the temp gauge giving you any warning.

And it wasn't my transmission specifically, it was thousands of transmissions at 13 shops over 7 years. That's why I say not to trust trans temp gauges when towing. They will indicate temperature problems that don't come from clutch slippage/shifting. But its the clutch slip/shifting that causes the most damage during towing.

In reply to curtis73:

Clutch slippage still adds heat to the fluid, so it will still show as a temp rise on the gauge. The big warning is, soft-engaging clutches will get significantly hotter than the fluid being fed into them. So the softer the trans shifts, the lower the "max safe fluid temp" should be treated as.

In my case, the TCC would have likely been fine had I kept the trans 20 - 30 degrees cooler. It had survived countless engagements under similar conditions with lower trans temps in the past. But this time, the fluid going into the clutch was hotter, so the clutch pack temps got even higher than normal and the thing couldn't handle it. Plus, running it hard with the TC unlocked meant the fluid in the TC was significantly hotter than pan temp, which heats the lockup clutch even more.

That's also why I target 160 - 180 as a running trans temp. 200 is my "I should probably ease off and cool this thing down a bit" threshold. If I see the gauge hit 210, it's time to pull over, trans in neutral, cooling fan forced to high speed to shed some heat.

Thinking about it, a temp sensor in the cooler feed line might be useful for seeing short-term temp spikes and knowing if you're going to fry something. That'll read hotter than pan temp, as it's usually converter output fluid (so it should be reading the hottest fluid that could possibly be getting fed into any clutch pack, etc.).

If you have to ask if you need 4x4 or not, you probably don't and you can save a PILE on the buy in by going 4 X 2. Your resale will of course be much lower. But if you don't need it, you're getting a better truck. What do I mean by that? The only thing 4X4 does better is go places where you need 4X4. It will be inferior in every other way except for that and the resale. It won't ride as nice, it won't haul as much, it won't pull as much, mpg will suffer, it won't handle as well, and it won't stop as well. Most of these short comings are just do to the extra weight. If you're just towing a heavy trailer and won't likely tow anyway when the roads are bad (like me), then by all means get the 2wd.

Finding one...now that's something else. You have to look almost exclusively in the south. But that's another advantage in itself.

Edit: and some of them, like older SuperDuty's, suffer tremendously in the turning radius department when equipped with 4X4.

Edit2: sorry. I only read the initial question and not the whole thread.

Jaynen wrote: I've read a lot of the other tow vehicle threads and have had my eye on the GMT800 3/4tons for a while. I considered a burban but feel like I really need the truck bed. Partially just because as a 3rd vehicle I think its easier to sell the wife on how useful a truck would be to have around than a SUV when we already have a minivan. I need a crew cab because I have two kids still in car seats and I think the extended cabs are a little tight from what I have read here. I am pretty much determined to just get a gasser and I think the 6.0 would be fine especially with some light mods from what I have been reading. I am not sure that I need 4x4, not enough to particularly seek it out but I will be towing a trailer and in the future possibly carrying a side by side to some unpaved area. So should I plan on looking for 4x4 specifically based on that? There seem to be quite a few of these trucks that go up for sale with over 200k but still running well, from the other threads people were suggesting that anything in the 100k to 200k was fine is 200k+ getting a little iffy? Are there any gasser crewcabs that I should be considering from the other makes? I am not brand loyal just want to have my eyes peeled for a good deal. It seems like most crew cab are either the short box or the longbed, do they come in crew+standard? I feel like a crewcab longbed 3/4ton would be quite unwieldy most the time?

Intake manifold gasket failure? Aren't these the 8 separate little gaskets like all LS1? How does that fail? This is new to me.

dean1484 wrote: I have a Sierra Denali with 320k. It has the 6l motor AWD other than normal ware items it runs like new. Now it is not a 2500 but it is a darn good truck. It is like taking a 1500 putting a Dana 60 in the back and the motor and trans from a 2500 in it. Oh before you start thinking of mixing the motor drive one. The 6.0 is a great motor in stock form. You would be better served spending on taking care of a couple known issues like the fan speed control, exhaust header bolts and intake manifold gaskets and the evap control solenoid and purge canister control. Lastly a fuel pump unless you have proof it was done in the last 25 k. Do all this and you will have a dam near bulletproof truck.

Carro Atrezzi wrote: Edit: and some of them, like older SuperDuty's, suffer tremendously in the turning radius department when equipped with 4X4.

The pre-05 ones with the leaf sprung solid axle front end lose about 10 degrees of steering angle compared to a 2wd or an 05+ 4wd with the coil sprung solid axle. If you're willing to do some work, the coil spring front end can be retrofitted with some parts swapping.

curtis73 wrote: Air gauge is for airbag helper springs. GVOD is worth big bucks. That is a sweet and beefy OD unit. That right there was a $3500 upgrade and will outlast the truck. The floor mount thing is obviously a tach. The thing beside the CB is a trailer brake controller. Not sure why the brake prop valve is inside the truck, but that's what it is. Come to think of it, not sure why there is one at all. Makes me wonder what else has been hacked about the brakes.

My wife's uncle who has owned the truck since new has been a driver for Hollywood for a couple decades driving big rings with generators often on them. I would guess with the air bags and expensive overdrive the wilwood unit is for a reason. Maybe he upgraded the brakes and needed to change the proportion Dunno why it would be in the cab tho.

Seems like it's well put together if he does want to sell

How much would you think this truck would be worth?

This PSD (second link) is almost identical to mine.

This truck will have 4.10 ring & pinon which, in my opinion, is too low unless you are working the pee out of it towing mini excavators and such. You won't see 20 mpg. This is a 16.5 mpg truck when babied and empty. By babied I mean 72 mph on cruise control. I also use an "Economy" tune. Otherwise it's a 16.0 mpg truck.

It is a good runner though. I'm not a coal roller by any means but the "Economy" tune wakes it right up. Once the torque converter locks up it will flat move. 60 to 80 is surprising for something that big and full of tools, gas, food, water, GF, dirt bike on hitch carrier, etc.

I do think I would be much happier with a 3.73 though. I think it would still have enough oomph to be fun but would the mileage would increase dramatically. I'm thinking that because my uncle has an F550 with basically the same setup. 2wd also but with 4:88's. That poor truck gets something like 9 mpg. That's just crazy for a diesel. There are a few guys out there grossing 80,000 lbs that are coming close to him.

The other thing is, the one in the ad is too low. I'm already scraping pavement with my hitch ball in parking lots. This thing looks cool but it's just too low.

Jaynen wrote: What about these slightly older 454 gassers ? http://www.racingjunk.com/Tow-Vehicles/182903728/1999-3500-Chevy-.html?sortby=price-lowest&page=3&categoryId=49&offset=23&from=category or this 7.3 powerstroke http://www.racingjunk.com/Tow-Vehicles/182895007/2000-F350-2WD-DRW-.html?sortby=price-lowest&page=5&categoryId=49&offset=41&from=category

Yeah I had been shopping 2000-2006 so was just curious if these slightly older trucks were still value

If I got to pick and choose, I'd definitely go 2wd crew, not that picky on engine for my needs since I wont be towing all the time like some folks do maybe 2 times a month for 3-4 hrs each way

Those pre-ABS trucks would lock the rear wheels under heavy braking when empty. I wouldn't be surprised if the proportioning valve was there to prevent that. Twist it one way when empty and back the other when loaded.

APEowner wrote: Those pre-ABS trucks would lock the rear wheels under heavy braking when empty. I wouldn't be surprised if the proportioning valve was there to prevent that. Twist it one way when empty and back the other when loaded.

This is almost certainly why the prop valve is in the cab. Some trucks use a setup that proportions the brakes based on rear ride height (so as the rear sags under load, it adds more rear brake). Proportioning needs are pretty different between an empty truck and one with an extra 2000 lbs on the rear axle.

Makes a lot of sense then. Seems like he went to a lot of trouble to fix up this truck towing related.

Are medium duty trucks a bad idea? Just looking it seems I could get a F-450 F-550 crewcab with a flatbed and less mileage for less money than older F-250 F-350 pickups

And most of the medium duty trucks also have diesels

http://www.commercialtrucktrader.com/listing/2006-Ford-F550--121040090

Medium duty trucks make a 3/4 ton look civilized. Not fun to ride in.

Hmm, I was looking at some of those stake bed dumps and thinking how you could probably use one to haul a car with the right ramps etc, or put a side by side on sideways and still tow a gooseneck

Carro Atrezzi wrote: Intake manifold gasket failure? Aren't these the 8 separate little gaskets like all LS1? How does that fail? This is new to me.

The manifolds warp, and even if they don't warp, O-rings can take a set and leak when cold.

The 1ZZ Toyota engines are especially common for this, too.