7.3 liter diesel swap tranny options

[heviarti]

A buddy of mine asked me a question, and I'm posting it here.

What he's in the middle of is swapping a dentside heavy truck body onto a 2001 F550. He'd have just done a front frame transplant, But he intends to use the truck commercially, and welded frames are frowned on, and the newer front end and steering are pretty much a neccessity. Also, if he'd have kept the rear section off the spud truck, he'd have not had disc brakes.

The big problem is the 7.3 is in front of a ZF S650 gearbox. Having driven the rig when it was all stock, I can tell you for sure that the ZF S650 sucks gigantic monkey &@!*s. It's feel is bad, it's throw is too tight, it's ratios tank, it's made of aluminum, and it's failure prone.

Is there a good cast iron gearbox that can be adapted easily to the 7.3? It doesn't have to be more than four speed, because there is a (maybe) usable Brownie box under (what was) the spud truck.

I've never run a split box, but I can learn, especially if it means no more .75 overdrive only, and maybe have something between the second and third gears.

Ideas welcome

[averagef250]

The ZF S-600 class of 6 speeds are great transmissions and have been well proven in all types of service since 1998. The ratios are perfect and the shift feel is better than average, if not the best for any modern 6 speed light/medium duty tranny.

Where you come up with this crap is beyond me, it makes absolutely no sense whatsoever and is entirely fabricated from baseless, backwards ideas.

[heviarti]

Short answer: Horse hockey.

Long answer...

I've put about five to eight hundred miles a month on an F-550 with the ZF, and the balance to fifteen hundred a month on one with the automatic (which is also lame).

I've been a bit further north than Spokane, East to Vernal, West to Bend, and South to some no name place in Nevada... I've hauled up to 30,000 pounds with the rig, and oversize to 10'x70' (with eight axles). Have you dealt with one that far or that long?

Before I went to work for the outfit they'd been through seven of those S-650s in less than six years. I got the most recent to last almost two years. I also have a five speed ZF in my BMW, which has also failed.

I've also driven Semi. I guess if you're comparing the ZF to a badly adjusted manual in a VW Rabbit, yeah... it shifts ok. If you're comparing it to a New Process 420/435, or an Eaton... or just about anything, it's dookie.

I've lost a station on the 650 (low/reverse) and one in my Beemer (3rd/4th)

The S650 is without a doubt *two gears* short. It should be an eight speed, with something between 2nd and 3rd, and a .83 overdrive between the direct and the .75 overdrive supplied. I honestly like the six speed in the 2001 Dodge 3500, but I'm sure it's too light a gearbox.

With a four speed and a four speed Brownie that's sixteen forward gears.... Where is the fault with that? Especially since I have to start in compound gear anyway...

250, have you ever driven a rig with the ZF installed? If so, have you done so loaded? If you've done either you can't tell me you didn't notice the fact the spring to the first station is waaaay too hard, and that you can't feel the teeth meshing when you shift? or that you can't feel the first/second and the third/fourth stations worth a darn? or the fact it takes an inordinate amount of effort to shift, or... oh yeah... the fact it's a stacked case made of *aluminum*?

Again, I'm looking for something to replace it with, with a Brownie if needed for having adequate gears.

[averagef250]

Heviarti,

ZF's aren't made of *aluminum*, in fact, almost nothing is made of *aluminum*, ZF's are made from aluminum alloy.

I have more experience than I care to type about with these truck transmissions. I have a few spare ZF transmission cases in inventory here in my shop. If you ever have the opportunity I invite you to stop by and take a 12 pound sledge to a ZF case and try to break it. It ain't gonna happen.

I've pulled around 35K up and down snoqualmie with 1/2 the gears and less break than that 550 has. I've pulled 25K up and down cabbage with an S6-650 behind a 5.9 Cummins in an F-350 and had power out my *ss.

My thought is the ZF 6 speed is actually in a higher class than the 7.3 PSD in front of it. My advice is if you think for a second it takes 16 gears and 2 sticks to efficiently move 30K you're dead wrong, you need more torque; a better engine.

Binder makes some great motors. They start with DT in thier names.

[heviarti]

Yes, I drive class A vehicles, and an 8 speed would be a small transmission... The smallest we've had was an Eaton Performance 9 speed in a 379 Pete with a C13. I started driving in a 379 with a C15 and a Super 10. I drove a 379 with a C15TT/heavy haul package and an 18 speed, A Mack with I don't know what Maxodyne and an 18... Freightliner Classic with a C15 and a 13 speed, and last week bobtailed a 379 with a regular 10 speed. The straight ten is the only one I was ever able to start in the high side, and generally most are started in the low side even unloaded.

I'd rather have one of the smaller Cats or a Power Tech, but an engine is a higher dollar item than a couple gearboxes. Surely there's something in a cast iron heavy duty box that has some feel?

I too have pulled Cabbage, with as much weight. Let me tell you what happens: I power out in third and drop to second, In second I have adequate acceleration and power to put it on the redline if I want. If I hit third again? I power out again.

my biggest concerns are the constant failures, and the really bad feel. I can deal with the bad ratios. I've personally experienced two different 650s in the truck and they both shifted awful. Nowhere near the feel of an NP or an Eaton. Another concern is the slave cylinder that provides no adjustment.

I'd love to have an IH with the DT466. unfortunately convincing the boss into a heavier truck is not a possibility. I've tried. If Railer-Bed was still around I'd have a tandem axle under the 550 already. I'm always on the lookout for an older Pete so I can haul a flatbed with one of them hang-on-the-back forklifts. It'd beat thowing axles by hand.

If I'm in your corner of the world You're welcome to try the other truck. If you tell me that's what you call 'good' you'll have to try my Power Wagon if you're in my corner of the world. I've put a lot of miles on the ZF, and never liked it. That's bringing in at least 20,000 pounds of product per week. I'll post a pic.

[heviarti]

Here's a pic of the one that's up, loading at Chubbuck, Id. I've put as many as 130 on the trailer, and filled the cage with one layer of rows over the top.

I weighed at a truckstop with 120, and 3/4 full of tires and weighed 39,800.

[averagef250]

You need a better motor and a better tranny builder. ZF's are tight, they shift like glass when they're set up right, bearings are preloaded correctly and a properly adjusted clutch. There are many moron tranny builders that set modern trannies up with old 1930's tranny clearance on the brain because they've never taken the time to LEARN how to work on the new ones. All the new stuff is this way. A dodge cummins NV5600 is not a very good tranny, a pretty sad one in fact and the ratios are the same as the ZF6.

When I've pulled cabbage in the mid 20,000's for weight I've done it in 5th and 6th with 3.73's and 33" tires with a mechanical 5.9 Cummins making a tick over 700 lb/ft @ 1600 and 300 HP. I had the power and gears to go up that hill a lot faster than the speed limit if I wanted to, but those curves shut anyone down at 55-60. The fact is the only reason I ever downshift into 5th on a (direct) is when I know the engine's verging on blowing right through the clutch.

PSD's take some work to make that kind of power, but they can. PSD's make power higher, they have a powerband that I don't particularly care for. I hate how they like sitting at redline under a load, to me that's a poor way to move a load. A 7.3 is a good engine in a 6000-10K pound truck. They pretty much suck at 20K+.

There are millions upon millions of very satisfied ZF 6 speed owners out there. They are one of the least worked on modern stick shifts out there. Under heavy service I'd expect a 200K service life from a Ford ZF6 speed.

[heviarti]

Tell ya what 250, next time we have one of these blow up I'll have the boss send it to you to rebuild if you want.... It'd just go to Bobby's transmission otherwise... and judging by the fact somebody else has been driving that rig for the last year, it won't be too long. I treat it a tad more gently than other people he has drive, so I might be able to get it to hang on a while. If it acts any better than the last two, I may keep it, and the one in the project will stay there. I've not yet blown one up, but I did have a shifter fork fail, and pulled it out, took it to Bobby's. Boss didn't listen when I told him there were shavings in the bottom of the gearbox. I quit not long after, and the box failed within two months after I left. He figured out the truck failed less when I drove it and called me back.

It'd a gone this last trip, but I was watching it. Next thing to do is figure out how I'm gonna cob a temp gauge to it. Went to do it last time but there wasn't a way to fit the sender in

I have on the otherhand blown the automatic they supply on the F550. Catastrophically, in the middle of nowhere, in the dead of winter.

[heviarti]

250, If I did not make clear what I said allow me to try this again:

If you think you can make one of these into something, I'm sure the outfit would happily pay for a rebuild from yourself as readily as they would Bobby's.

If you feel you can get one of these to shift worth a darn, and feel like gears instead of a piece of rubber in pudding, I'm perfectly ready to let you demonstate your skill and be paid for doing so.

I don't particularly like the powerstroke either, it's gutless and it's a V8. I'd much rather have a small Cat, a Power Tech or a Cummins In that order. I'm helping with the cab electrics in the conversion job, but for the most part I refuse to work on anything newer than 1972 if it involves something I think is badly designed, or involves electrics. So, shoehorning in anything that's not mechanical injection is out for me.

[TX69F100]

7.3 PSDs can make decent power with nothing more than injectors/turbo/tuning. ~475rwhp/1000ftlbs can be had pretty easily on a tow-friendly combo. Not exactly gutless...

[speed bump]

I will agree that the 7.3L is pathetic, I just picked up my work truck with a 7.3L and its horrible. I'm pretty sure my last V-10 service van had more power, of course it could be the auto transmission.

As far as hating Diesel ratio ZFs and liking NP435s I don't know what to tell you, I would dump my NP-435 in a heartbeat if I could put a ZF-5 or 6 in my truck. The ratios are right and it has a much better shifting feel as well.

[heviarti]

I dunno man, you might be able to get the power, but not the reliablilty. That rig in the pic has gone through seven engines that I know of.

[TX69F100]

I've had two 7.3L PSDs with ~200k miles and were still running strong when I sold/traded them. Both were driven hard.

[averagef250]

7.3 PSD's typically last 150-200K when they are loaded above 20K continuously. Believe it or not the 7.3 N/A IDI's usually outlast them, they get a pretty solid 250K doing the same job, just a lot slower.

The T444E/ 7.3 PSD does great in pickups and even has a strong reputation in medium duty applications where it's run empty or light loaded most of the time, one example that comes to mind is tow trucks.

They are not bad engines, they can make good power, but they are on the extreme lower end of what could be considered a medium duty engine. They were designed by Binder as a base model throwaway engine for thier medium duty truck/bus apps, but Ford ate them up as a decent V8 diesel that fit in thier trucks. These engines were not designed very ruggedly, not like a B or C Cummins or a DT360 or DT 466 Binder is. A B Cummins or DT will make it's rated nameplate power and torque for 350,000 miles with oil changes and valve adjustments. A 7.3 PSD will be lucky to make 1/2 that doing the same. Granted, most pickups never push the engines close to that, but that's just how it is.

[TX69F100]

By "Binder", are you referring to International?