Transmission Upgrade?

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AaronW

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Hi all:

I've just recently got my 89 V3500 back on the road. It's got the TH 400 transmission in it. 454 motor. I can't remember what the rear end gearing is (I didn't mess with it). When I discussed it with the machinist who rebuilt my engine, he didn't think I'd get more than 1 or 2 mpg improvement, going to a 4 speed automatic trans, and since the one I've got was in pretty good shape, we just left it. I'm still finishing the interior, so the cab will quiet down some when I get the door panels back on, however, I think it's still going to be pretty loud in there at 65 or 70 mph. If I had been going to upgrade, the 4L80e was on the radar.

However, I just took a run out east, for a friend, to pick up a large piece of equipment, and I drove is 2020 Ford diesel 1 ton dually. It had a 10 speed trans in it, and to put it mildly, it was awesome. (yeah, I know, here come the Ford haters, and yes, that truck has like twice the torque mine does, even with the major rebuild). This got me to thinking, what other transmission options are there, that would be good on a 454? I'm really just in the musing phase, at present. It would be a few years before I did anything.

Aaron
 
Bextreme04

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AaronW said:
Hi all:

I've just recently got my 89 V3500 back on the road. It's got the TH 400 transmission in it. 454 motor. I can't remember what the rear end gearing is (I didn't mess with it). When I discussed it with the machinist who rebuilt my engine, he didn't think I'd get more than 1 or 2 mpg improvement, going to a 4 speed automatic trans, and since the one I've got was in pretty good shape, we just left it. I'm still finishing the interior, so the cab will quiet down some when I get the door panels back on, however, I think it's still going to be pretty loud in there at 65 or 70 mph. If I had been going to upgrade, the 4L80e was on the radar.

However, I just took a run out east, for a friend, to pick up a large piece of equipment, and I drove is 2020 Ford diesel 1 ton dually. It had a 10 speed trans in it, and to put it mildly, it was awesome. (yeah, I know, here come the Ford haters, and yes, that truck has like twice the torque mine does, even with the major rebuild). This got me to thinking, what other transmission options are there, that would be good on a 454? I'm really just in the musing phase, at present. It would be a few years before I did anything.

Aaron
Click to expand...
Anything with more than 4 speeds is going to be fully electronically controlled... and expensive. A 6, 8, or 10 speed isn't going to do much on getting the upper speed RPM's down though. The 10th gear in either the GM Allison 10 speed or the Ford 10R140 are both ~.63:1 ratio, which is close to the same as a GM 6L80/6L90 which is .667. 4L80 is a .75 4th gear ratio.

For real world comparison @ 70mph, if you have a 31" tire and 3.73 rear gears(very common ratio for 454's), that puts you at the following engine RPM if you are in the final gear of these transmissions:

1) TH400 : 2830 RPM
2) 4L80E: 2122 RPM
3) 6L90E: 1887 RPM
4) 10L Allison: 1782 RPM

The 4L80 would put you right in the sweet spot for the 454 at highway speeds. The 6 or 10 speed is going to be kind of lugging at freeway speeds unless you have smaller tires or a taller rear gear. I have 4.10's and 35's on mine and the fuel injected 454/4L80 combo should sit at ~2000RPM at 70mph. Because I'm running fuel injection on the 454 I already have the controller for the 4L80, but if you are staying with a carb on your 454, you will likely need to either go full manual on it or run a stand alone controller. Either one can have some downsides
 
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Bextreme04 said:
Anything with more than 4 speeds is going to be fully electronically controlled... and expensive. A 6, 8, or 10 speed isn't going to do much on getting the upper speed RPM's down though. The 10th gear in either the GM Allison 10 speed or the Ford 10R140 are both ~.63:1 ratio, which is close to the same as a GM 6L80/6L90 which is .667. 4L80 is a .75 4th gear ratio.

For real world comparison @ 70mph, if you have a 31" tire and 3.73 rear gears(very common ratio for 454's), that puts you at the following engine RPM if you are in the final gear of these transmissions:

1) TH400 : 2830 RPM
2) 4L80E: 2122 RPM
3) 6L90E: 1887 RPM
4) 10L Allison: 1782 RPM

The 4L80 would put you right in the sweet spot for the 454 at highway speeds. The 6 or 10 speed is going to be kind of lugging at freeway speeds unless you have smaller tires or a taller rear gear. I have 4.10's and 35's on mine and the fuel injected 454/4L80 combo should sit at ~2000RPM at 70mph. Because I'm running fuel injection on the 454 I already have the controller for the 4L80, but if you are staying with a carb on your 454, you will likely need to either go full manual on it or run a stand alone controller. Either one can have some downsides
Click to expand...
Thanks for the info, Eric. Mine was a stock TBI, but we went back to a 4 barrel carb on it. I think my tires are 33's, I'll have to check for sure. How do you check the rear end gearing? Does it say, on the differential? I'm kinda a newb at this stuff. Regardless, I'll be getting down to 2000 or so rpm would make a pretty big difference. Would you agree that my mpg wouldn't likely improve all that much? I was getting about 5-6 mpg before the rebuild. Have only put maybe 500 miles on it so far, but I say I'm now averaging around 9 mpg.

Aaron
 
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AaronW said:
Thanks for the info, Eric. Mine was a stock TBI, but we went back to a 4 barrel carb on it. I think my tires are 33's, I'll have to check for sure. How do you check the rear end gearing? Does it say, on the differential? I'm kinda a newb at this stuff. Regardless, I'll be getting down to 2000 or so rpm would make a pretty big difference. Would you agree that my mpg wouldn't likely improve all that much? I was getting about 5-6 mpg before the rebuild. Have only put maybe 500 miles on it so far, but I say I'm now averaging around 9 mpg.

Aaron
Click to expand...
Should be good for a few MPG... especially on the freeway. The combination of getting the RPM down and locking the converter up should make a huge difference. Most of the guys running the Gen V and Gen VI 454/4L80 combos report somewhere between 12-14mpg, but I don't have any real world experience on that yet. Unfortunately, you shot yourself in the foot a bit by getting rid of the TBI. It's pretty easy to run a cheap 0411 ECU and piggyback all the required inputs you would need to control the transmission from the TBI sensors. You really just need TPS and engine RPM for the factory computers to control all that. You could also just swap in a newer 96 or later 454/4L80 combo all at the same time with an 0411 as a standalone. You would then have multiport fuel injection and the 454 all together. The Gen VI heads are much better than the TBI ones. Or go even newer and an 8.1/4l80 or an 8.1/Allison combo. They can be had as a running combo for under 2k with the wiring harness and computer.
 
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4l80e would be the likely choice. 6 speed would allow to have steeper 1st gear for quick take off.
I was getting about 12mpg with gen6 454 and 4l80e in a 4x4 suburban(33" tire). At one time had a 2wd crew cab with gen6 454 and nv4500 that would get up to 16-17mpg. Currently with a 488 motor in a suburban tend to get right at about 10mpg highway.
 
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AaronW said:
Thanks for the info, Eric. Mine was a stock TBI, but we went back to a 4 barrel carb on it. I think my tires are 33's, I'll have to check for sure. How do you check the rear end gearing? Does it say, on the differential? I'm kinda a newb at this stuff. Regardless, I'll be getting down to 2000 or so rpm would make a pretty big difference. Would you agree that my mpg wouldn't likely improve all that much? I was getting about 5-6 mpg before the rebuild. Have only put maybe 500 miles on it so far, but I say I'm now averaging around 9 mpg.

Aaron
Click to expand...
A quick way is to turn both wheels together exactly one turn and see how many times the driveshaft turns- that will be a rough ratio for you.

You can also pop the rear cover off and it’ll have the number of teeth for the pinion and ring gear stamped in the outside of the ring gear itself. Do the division and that’ll tell you the exact number.
 
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You're gonna spend a LOT of cabbage to turn an inefficient brick into a slightly better inefficient brick regardless of engine and tranny choice. I have a vortec 350, multi port efi and manual overdrive. I get an honest 15 mpg at best on the highway. We don't drive these antiques for efficiency.
 
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Honestly,at this point you need to put a tach in it and see what rpm you are really turning with what you've got. And only you can feel and tell at what rpm the engine makes enough power to pull its own weight. Drive at the rpm you think you want, and see if the engine bucks etc. Speed you're driving at,at that rpm is irrelevant we want to see how your engine behaves at your target rpm
 
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The simplest/most cost effective swap will be the 4L80E and a stand alone controller. However, if the budget is there, you can also look at 6L80 or 6L90s. My buddy is about to put a 6L80 behind his 454 in his '86 CCLB with a stand alone controller. The overdrive ratio stays similar to the 4L80, but you get more grunt off the line with the 6L.
 
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Putting a camper shell on it will give you 2 or 3 more MPG on the freeway, as the open bed acts like a big air brake that you engine is always working against. But nothing is going to give you Japanese-like mileage if that's what you are looking for.

J.B.
 
Frankenchevy

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JBswth said:
Putting a camper shell on it will give you 2 or 3 more MPG on the freeway, as the open bed acts like a big air brake that you engine is always working against. But nothing is going to give you Japanese-like mileage if that's what you are looking for.

J.B.
Click to expand...
Most studies show this to be incorrect.
 
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Frankenchevy said:
Most studies show this to be incorrect.
Click to expand...
I remember Mythbusters did this on two different episodes back in the day because people didn't believe the results the first time. Driving with an open tailgate gave the worst mileage, and driving with a closed tailgate gave the same mileage as having a bed cover. The open bed with a closed tailgate creates a vortex that helps air passing over the cab continue on unimpeded. Oddly enough, they got the best mileage with a net style tailgate.
 
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Bloodhound1981 said:
I remember Mythbusters did this on two different episodes back in the day because people didn't believe the results the first time. Driving with an open tailgate gave the worst mileage, and driving with a closed tailgate gave the same mileage as having a bed cover. The open bed with a closed tailgate creates a vortex that helps air passing over the cab continue on unimpeded. Oddly enough, they got the best mileage with a net style tailgate.
Click to expand...
Yep. There’s quite a bit of wind tunnel data shows what happens behind the cab with the tailgate closed vs camper shell. The air clears the rear of the truck more cleanly with an empty bed, tailgate shut. Also, camper shells obviously add more weight.

Back to the thread…

Best case swapping in an auto would be anything with a lockup and OD.

How long will it take to recoup the money spent on the swap, in realized gas savings? That’s the question…
 
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