I have a 85 MC SS running a 383 with a Turbo 350 transmission I had 411 gears in the car traded them with a friend of mine for a rear end with some 320 somethings I with the 411 gears my car would be at 3800 rpms before I reached 60 mph definitely geared for the track in my process of turning my car into a street car im wondering do I need to change my transmission as well or will these higher gears allow me to drive the car longer distance at a faster speed without my rpms being so high
G-body drivetrain
- Thread starter lowkeyfromUptown
- Start date
Not everyone wants or needs 4.11 gears and a 3 speed automatic. Some people do want to drive their cars to the next town over or blast down the highway at 80. It just all depends on where you want to live and drive on the RPM scale while doing it. Stop light to stop light, put your big boy pants on and get 5.13s and STFU. You'll be in the power band from the get go. But don't think you're going to drive it to the G-body meet in Cleveland or something unless you leave a week in advance and take the back roads. Trailer it maybe. Drive it...if you like living in the upper RPM band I guess.
Screwz - As far as 4L80E, you can probably keep your 4.11 gearing if you drop in the OD trans. I'd do that first, and then if you still feel the need to go 3.73 then do that. You may find you don't need to. If you're not going to hop on the highways with it, then you likely don't need to jack with the rear end gearing with an OD.
Screwz - As far as 4L80E, you can probably keep your 4.11 gearing if you drop in the OD trans. I'd do that first, and then if you still feel the need to go 3.73 then do that. You may find you don't need to. If you're not going to hop on the highways with it, then you likely don't need to jack with the rear end gearing with an OD.
There is no reason to change the 3 speed out because of this change. You likely have a 3.23 if you have a GM 10 bolt. If you know your tire height there are online calculators that will tell you what RPM you will run on the highway. You have a perfectly street able combination.
With my 200R4 and 3.73 gears, I turn 2000 rpm at 65 MPH. At cruising highway speed I like for the motor to be around 2000. IMHO that is the optimal range for your motor.
I wonder if you're going to see a whole lot of benefit? Why the change then?
To get a good 4l80e ($1000+?) costs for to have it gone through ($1000+?) a controller ($1000+?) costs related to crossmember, mounts, fluids ($500+?) You're probably above $3000 plus time to install a unit that draws a bit more power and weighs more.
But you aren't interested in highway driving at speed which is where the OD kicks in and saves gas mileage.
To cover costs of install. Everything else being equal, you'd need to save about 1000 gallon of gas as well.
Crunching the numbers in an arbitrary manner, lets say you jump 16mpg to 20 mpg. So that 1000 gal represents needing a savings of 20,000 miles. At a 4mpg savings per gallon, you'd burn 5,000 gallons to get that. And 5,000 gallons at 20mpg again means driving 100,000 miles before break even, and, that doesn't account for time/value of money, inflation, interest/appreciation you could get by investing elsewhere...
End of the day, in a back roads corner carver the OD benefits aren't there compared to a cheaper th400 unit. And to break even if the motivation is to save gas it takes a LONG time for OD to pay off..
If your concerns were too high rpm on highway there's a benefit beyond savings.. or you blew a trans and needed to buy something because you have nothing right now the analysis changes. Then it's the cost difference between 3spd and 4spd you need to save to have it pay off.
I argued with a horses *ss on Classic Olds that, especially up here with everything a long distance, running at 3500 rpm for hours is far from ideal. He said his Kia happily ran down the road a 4000+ rpm for long distances, really how is a 4cyl comparable? So his newly built Olds 350 with a TH350 and 3.42 gears at 80 mph is puking oil in the catch can. He wanted to go back to stock valve covers to fix it and was talking to the machine shop about ring seal🤣. I'm sorry, many 3.91 3 spd factory cars motors lived short lives for a reason. I have drove too many modern vehicles to have my car screaming down the highway.
I get what your saying about the cash.But I also get to sell the TH350 and stall converter and why start with a good 4l80e and not just a core at half the price. Or just put a good used transmission in. There’s always ways to save money.
My goal is to make the car/truck more modern to drive. I live in an area that has a lot of good back roads and amazing views. I feel it would be much nicer to drive with an OD . And it would also make it more desirable for resale. I would definitely want a 4l80e over a TH350.
I will recommend a 4l80 over a 200-4R or 700-R4 just for the shift smoothness, but get ready to pay.
How are you going to control it?
How are you going to control it?
Don't get me wrong, 4l80e is a good trans. But it's going to be a very expensive luxury upgrade where it doesn't seem you make the power now, or plan to in the future. Sort of like putting a 9" rear behind a 2bbl 231 buick because I wanted to swap gear ratios 😉
It's one of those upgrades that there isn't a real good budget way to make happen. A used th350 and converter isn't going to bring you even $1000 to offset. And the junkier 'core' 4l80 you start with, the more expensive it's going to cost in the end. Much cheaper to refresh a decent used one.
Look into the stand alone controllers, those are about $1000 on their own by the time you get it in the car. Not a simple swap like a 700 or 200 series OD, it NEEDS a standalone computer to run it unless you're swapping in an engine with a computer that's already programmed to run a 4l80/4l85.
I'd say make up a spreadsheet of the parts you need, from crossmember on upwards and make sure the budget fits. It's just one of those upgrades there aren't corners to be cutting.
The only corner that could be "cut" (I wouldn't do it) would be during the rebuild/refresh put in a manual valve body... But that will mean manually shifting an auto trans just to eliminate the controller.
The factory gears in my '78 Caballero are 2:73s. Coupled to a 305 V8, it's fairly sedate, but that's fine by me.
My '72 Chevy C20 pickup came with 4:11 gears ,which was great for it's original use hauling a big slide in camper up and down the foothills of the Rockies, but not so great on Ontario's expressways. We installed a set of 3:73s which helped some. The really noticeable change came with the installation of a 700R4 auto. Now it can cruise at whatever reasonable speed you wish, and still has the balls to pull my car trailer.
The trick is to get an older 700 that doesn't need a computer.
My '72 Chevy C20 pickup came with 4:11 gears ,which was great for it's original use hauling a big slide in camper up and down the foothills of the Rockies, but not so great on Ontario's expressways. We installed a set of 3:73s which helped some. The really noticeable change came with the installation of a 700R4 auto. Now it can cruise at whatever reasonable speed you wish, and still has the balls to pull my car trailer.
The trick is to get an older 700 that doesn't need a computer.
- Status
Similar threads
