I'd like to bounce this around with y'all and see what you think.
My truck's an 01 International single-axle 4900 w/ 215 hp HT DT466E with Eaton-Fuller FS6406A 6-speed transmission, direct drive high gear. Rear end is a Meritor RS21145 with air locker (DCDL) and 5.13 gears. It's an ex-utility truck, thus the low gearing. I don't quite make 60 mph at 2600 RPM in high gear. I'm getting 7.5 mpg right now. Truck weighs just below 20,000. By the time I get a crane mounted it should be right around 23,000. GVW is 33,000. Air brakes, etc.
The truck has 4,300 hours on it and 77k miles. Just had a crankcase pressure test done and it only showed 2.2 psi, so the engine's still like new. Plenty of power, I can cross the Blue Ridge mountains without dropping out of high gear.
I want to save my engine by dropping my highway RPM's considerably, but not lose my low forward and reverse ratios because I spend time off road on farms and jobsites. I also don't want to lose my air locker in the rear. If I could, I'd like to gain a mpg or two in the process. I have a few options, and since I'm fairly new to medium-duty trucks (my last svc truck was an F550) I'd like some advice if you have the time. Here are a couple things I could do:
1. My Int'l dealer can get me a reman 4.33 center section with air locker, my cost would be $1850 for it, with my current center section going in for core. Plus tax, oil, and axle seals. This would drop my highway RPM's some but my low gear and reverse would get faster too. Don't really like that - I like my creeper low speeds. At highway speeds, I'd go 50 mph at 1800 RPM, and 67 mph at 2400 RPM.
2. Been reading on Eaton-Fuller's website, and I'm thinking about an 8LL transmission. Actually two different ones.
- The first and most expensive option is the RT-8908LL. This has a direct drive high gear but double-reduction low-low and reverse gears. I'd still need to swap the rear gears also, to get better highway speed out of it. That's what makes it most expensive. Highway speeds would be the same as the 4.33 gear swap.
- Or I could go with one of the RTO 8LL transmissions, either the 11908LL, 14908LL, or 16908LL. All of these, and the 8908LL weigh the same and have the same dimensions according to the website. I'm assuming the only differences are the heat-treating on the gears. The RTO 8LL transmissions have a .74 overdrive high gear in addition to the double-reduction gearing on the low end. I've looked at the ratios and although a little higher across the board than the 8908LL's, they'd be just fine. With one of these RTO trans's, I'd get highway speeds out of my existing 5.13 rear - 57 mph at 1800 RPM and 70 mph at 2200 RPM.
That option would be a no-brainer, except I'm wondering about heat buildup in the rear over extended drive times. Some of my jobs are 3 or 4 hours away, and those 5.13's would really be humming back there at 70 mph interstate speeds.
The other deal with the 8LL's is that even though Eaton-Fuller says they're availabe in SAE # 2, they aren't really. I spent hours on the phone with them today. You can get a # 2 clutch housing for them, but the input shaft remains 2" instead of 1.75", and they keep the larger 1.18" pilot bearing also. Did some more checking. I can get an SAE # 1 flywheel housing for the DT466E and use whatever used 8LL I find just like it is. I think. So it'll take a little work to get an 8LL into this truck, but I don't see a reason it couldn't be done.
Last option was to find an old RTO-6613 light-duty 13-speed transmission which is already SAE # 2 and has double-reduction on the lowest gears and overdrive on top, but it has a low 660 ft-lb torque rating and I'd like to keep the drivetrain pretty stout in case I want to replace it with a 250 hp DT466E or a healthier DT530E one day. The 6613's torque rating barely would work with the engine I already have (which is 620 ft-lbs).
So what would you do if it was yours?
My truck's an 01 International single-axle 4900 w/ 215 hp HT DT466E with Eaton-Fuller FS6406A 6-speed transmission, direct drive high gear. Rear end is a Meritor RS21145 with air locker (DCDL) and 5.13 gears. It's an ex-utility truck, thus the low gearing. I don't quite make 60 mph at 2600 RPM in high gear. I'm getting 7.5 mpg right now. Truck weighs just below 20,000. By the time I get a crane mounted it should be right around 23,000. GVW is 33,000. Air brakes, etc.
The truck has 4,300 hours on it and 77k miles. Just had a crankcase pressure test done and it only showed 2.2 psi, so the engine's still like new. Plenty of power, I can cross the Blue Ridge mountains without dropping out of high gear.
I want to save my engine by dropping my highway RPM's considerably, but not lose my low forward and reverse ratios because I spend time off road on farms and jobsites. I also don't want to lose my air locker in the rear. If I could, I'd like to gain a mpg or two in the process. I have a few options, and since I'm fairly new to medium-duty trucks (my last svc truck was an F550) I'd like some advice if you have the time. Here are a couple things I could do:
1. My Int'l dealer can get me a reman 4.33 center section with air locker, my cost would be $1850 for it, with my current center section going in for core. Plus tax, oil, and axle seals. This would drop my highway RPM's some but my low gear and reverse would get faster too. Don't really like that - I like my creeper low speeds. At highway speeds, I'd go 50 mph at 1800 RPM, and 67 mph at 2400 RPM.
2. Been reading on Eaton-Fuller's website, and I'm thinking about an 8LL transmission. Actually two different ones.
- The first and most expensive option is the RT-8908LL. This has a direct drive high gear but double-reduction low-low and reverse gears. I'd still need to swap the rear gears also, to get better highway speed out of it. That's what makes it most expensive. Highway speeds would be the same as the 4.33 gear swap.
- Or I could go with one of the RTO 8LL transmissions, either the 11908LL, 14908LL, or 16908LL. All of these, and the 8908LL weigh the same and have the same dimensions according to the website. I'm assuming the only differences are the heat-treating on the gears. The RTO 8LL transmissions have a .74 overdrive high gear in addition to the double-reduction gearing on the low end. I've looked at the ratios and although a little higher across the board than the 8908LL's, they'd be just fine. With one of these RTO trans's, I'd get highway speeds out of my existing 5.13 rear - 57 mph at 1800 RPM and 70 mph at 2200 RPM.
That option would be a no-brainer, except I'm wondering about heat buildup in the rear over extended drive times. Some of my jobs are 3 or 4 hours away, and those 5.13's would really be humming back there at 70 mph interstate speeds.
The other deal with the 8LL's is that even though Eaton-Fuller says they're availabe in SAE # 2, they aren't really. I spent hours on the phone with them today. You can get a # 2 clutch housing for them, but the input shaft remains 2" instead of 1.75", and they keep the larger 1.18" pilot bearing also. Did some more checking. I can get an SAE # 1 flywheel housing for the DT466E and use whatever used 8LL I find just like it is. I think. So it'll take a little work to get an 8LL into this truck, but I don't see a reason it couldn't be done.
Last option was to find an old RTO-6613 light-duty 13-speed transmission which is already SAE # 2 and has double-reduction on the lowest gears and overdrive on top, but it has a low 660 ft-lb torque rating and I'd like to keep the drivetrain pretty stout in case I want to replace it with a 250 hp DT466E or a healthier DT530E one day. The 6613's torque rating barely would work with the engine I already have (which is 620 ft-lbs).
So what would you do if it was yours?
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