help me understand gvcw of idi compared to 460

[OneUglyNerd]

I have a 92 f-350 crew cab 7.3 idi 4.10's automatic. I like the truck but have looked in my owners manual to find out the gvcw and I believe its 17000. With that being said a 460 with the same specs gvcw is 18000 and if both trucks were fitted with 5.13's the diesel's gvcw is 18000 and the gas burner 26k. I'm no towing genious but can someone help me understand this... First of all I thought diesels were better for towing and I also thought manuals were better as well. In the owners manual the manual transmissions were significantly lower in towing rating compared to auto. Any help understanding this would help. thanks

[gmoore]

The '92 is a non turbo'd engine. It does not have the power of a 460 gas engine. Add a turbo system to the engine and things change alot. I had a '93 with factory turbo. Minor mods to the exhaust, timing, and gauges, made it a towing machine.

The manual transmissions are rated lower, due to the clutch assembly. The idi 7.3's used a two piece flywheel and few other unusual parts. Most people go to a one piece flywheel at clutch replacement time. It's cheaper and works better.

I did a lot of towing at 20k GCVW with no problems or broken parts.

Good luck

[LMJD]

Manual trans trucks have generally had a lower tow rating because the mfgrs have no control over driver clutch abuse when towing heavy loads so they error on the safe side.

[SmokeyWren]

Gross combined weight rating (GCWR) is the weight a combo of engine and drivetrain can get moving and then tow up a certain grade at a certain speed without overheating something.

So at that speed, up that hill, while grossing 18,000 pounds, the stock 460 can make it to the top without overheating or straining anything. The stock IDI non-turbo diesel has fewer horses, so it can't make it to the top of the pass with more than 17,000 pounds at that speed without overheating something.

As to stick shifter vs. automagic tranny, the key is getting the load moving. The automagic has a torque converter that almost doubles the torque coming from the engine at slow speed, so with the torque converter slipping and creating a volcano worth of wasted heat while doubling the torque available to the tranny, the load begins moving without "slipping the clutch". Yes, the torque converter is slipping, but it's designed to slip with no problem other than creating a bunch of heat that must be sucked out of the tranny fluid by a huge tranny cooler.

The stick shifter can tow the same weight after you get it moving, but you have to slip the clutch too much to get it moving. So the automagic has more GCWR.

That was then. Beginning with the SuperDuty pickups in '99 model year, Ford beefed up the stick shifters with a heavier-duty clutch and tranny, so the stick shifters had the same GCWR as the automagics.

[OneUglyNerd]

thanks for all the help. I knew that you guys would make since of this. With my set up can I get some suggestions to increase my gvcw safely. The things I have done so far are add a 4 spring pack helper spring set up. Extra trans cooler and the shift kit on the auto transmission rebuild. I want to add a turbo but have heard you really need to rebuild the motor to handle the potential heat. My mechanic said I could potentially melt the motor with a turbo. Also I don't know if there are better brakes I can put on. I know with sports cars the drill rotors, increase size of braking components and things like that. Any ideas there? Thanks again

[SmokeyWren]

Originally Posted by OneUglyNerd

My mechanic said I could potentially melt the motor with a turbo.

Then your mechanic assumes you're too dumb to install additional gauges with the turbo mod, and then drive by the gauges.

Rule 1 is to install easy-to-read-at-a-glance pre-turbo pyrometer and turbo boost gauges, then drive by the gauges and NEVER exceed the red lines of 1,250° pre-turbo exhaust gas temp (EGT) or 25 PSI boost. With a stock tune for a turbo engine, that's easy. But if you have a towing tune that adds fuel to the fire to produce more horses for dragging a trailer up the mountain, then it requires close attention and self discipline to stay below the limits. Your incentive to stay below the red lines is it's very easy to melt a piston or blow up a turbo if you exceed the red lines.

[gmoore]

The idi 7.3 is all mechanical, NO tunes (computer control). About the most boost that you can get out of most idi 7.3 turbo systems, 15psi.