y5mgisi
1 ton status
I think you would be best off with the 2.43/4.33 unit.
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Saying Good-bye to the 90 and Hello to the 72 Build. NEW:Hidden Exhaust
- Thread starter GRINCH
- Start date
friend has a 4l80e/241 out of a straight axle 91 1-ton crew cab here in powell he is looking at selling for a pretty fair price if that is a route you are considering.
GRINCH
1/2 ton status
I did some checking and the ECU from TCI runs about $600. Not sure if it is worth it or not. The 4l80 has the same gears... Just a bonus of OD.
Pm me the details
Pm me the details
Having an OD tranny could give you a lot more possible options with axle gears (deeper)... that would allow you to "fine tune" the performance for sand or snow and still give you good highway RPMs.
You should run a few scenarios with 4.56, 4.88 and 5.13s to see how they look compared to the chart above... maybe there's a combo that works well for both sand and snow?
You should run a few scenarios with 4.56, 4.88 and 5.13s to see how they look compared to the chart above... maybe there's a combo that works well for both sand and snow?
GRINCH
1/2 ton status
You should run a few scenarios with 4.56, 4.88 and 5.13s to see how they look compared to the chart above... maybe there's a combo that works well for both sand and snow?
I would if I understood them better...
I do think the 4l80e would help but the co$t to do it is getting up there. It may be something I might do down the road. I have been reading all day on the conversion. Bottom line is it will run almost a $1000.00 plus the cost of the tranny.
I already have the 400.
What do you think of the switch pitch idea?
More reading here. http://www.442.com/oldsfaq/oftsp.htm#SP TransDetail
How about the Lower 1st gear 2.75 vs 2.48.
If I use a 3.73 gear vs 4.10 on the calc i found the rpms drop and the MPH increase. But you say look at 4.56 or 5.33's
Can you run some numbers for me?
The deeper axle gear is like getting a deeper 1st gear ratio... actually it's like making EVERY gear in the transmission deeper. If you want more grunt off the line, the deeper axle gears will do that for you....but without the OD transmission you'll run out of top-end. Deep axle gears REQUIRE the OD tranny. If that's off the table, there's no point running the calcs.
The formulas are pretty simple, multiply the gear ratio * transfercase gearing * axle gearing..... for a crawl ratio below the converter stall multiply that result X2 to compensate for the gear reduction caused by the slipping converter. Once the converter stalls, the multiplier becomes X1 (effectively goes away once the converter is spinning at the same speed as the engine)
As for the switch-pitch TC idea, it sounds more like a gimmick than a solution especially with a big-torque Caddy motor. You're going to have all your torque down low in the powerband, so I don't really see the benefit of using a stall converter so far above the peak torque of the motor.... it seems mismatched to the application (heavy truck with lots of TQ).
Ultimately, you need to figure out where you want to spend your money. Putting custom gearsets into a TH400 isn't cheap, and neither is a STaK box.....neither is a 4L80E solution... for that matter, neither is regearing two axles to change from your existing ratio to something deeper (or shallower).
I think another thing you should start factoring in is the fact that you are not comparing apples-to-apples when it comes to engines. The MUCH more powerful Caddy motor will allow you to use a lot less gear and still have the same amount of TQ to the wheels that you had before with that smaller motor. If you don't compensate for the fact that you're going to be adding a lot more power, your gearing is going to get you a lot more wheelspin, and a much quicker trip around the tachometer in each gear, but perhaps not much useful acceleration.
The formulas are pretty simple, multiply the gear ratio * transfercase gearing * axle gearing..... for a crawl ratio below the converter stall multiply that result X2 to compensate for the gear reduction caused by the slipping converter. Once the converter stalls, the multiplier becomes X1 (effectively goes away once the converter is spinning at the same speed as the engine)
As for the switch-pitch TC idea, it sounds more like a gimmick than a solution especially with a big-torque Caddy motor. You're going to have all your torque down low in the powerband, so I don't really see the benefit of using a stall converter so far above the peak torque of the motor.... it seems mismatched to the application (heavy truck with lots of TQ).
Ultimately, you need to figure out where you want to spend your money. Putting custom gearsets into a TH400 isn't cheap, and neither is a STaK box.....neither is a 4L80E solution... for that matter, neither is regearing two axles to change from your existing ratio to something deeper (or shallower).
I think another thing you should start factoring in is the fact that you are not comparing apples-to-apples when it comes to engines. The MUCH more powerful Caddy motor will allow you to use a lot less gear and still have the same amount of TQ to the wheels that you had before with that smaller motor. If you don't compensate for the fact that you're going to be adding a lot more power, your gearing is going to get you a lot more wheelspin, and a much quicker trip around the tachometer in each gear, but perhaps not much useful acceleration.
Last edited:
Not sure about the condition of your th-400 but I will say fair warning if you plan on building it to handle the caddy motor.
I have well over $1000.00 in mine and yes it's bullet proof but it's still only a three speed tranny.
It's not always about just the cost but the end result, basically talking about better drive-ability.
GRINCH
1/2 ton status
I have decided to run the 4l80e and will be using my old 241. I would like to go with the STAK but another 3K is really cramping the budget. Maybe down the road if I am not happy with the final setup.
I have a few options to consider with the 4l80E.
I can run the stock planetaries of 1st @ 2.48 and 2nd @ 1.48 or for $600 I can have
it with 1st @ 2.75 and 2nd @ 1.57.
Another thing I want to add is a manual/automatic valve body. There are times that starting out in second may help with tire spin.
From what I read most Caddy guys are running an 1800-2000 stall convertor. Here's the specs on the caddy motor. 420 HP@3800 547 Ft-Lbs@ 3200. The powerband is much lower than my SBC was. . A lower stall will also help with heat build up.
I'm still trying to understand all the gearing calculators out there and what the numbers mean. I have the basics down but when trying to figure out a good crawl ratio vs what will be best for drags i'm lost.
I have a few options to consider with the 4l80E.
I can run the stock planetaries of 1st @ 2.48 and 2nd @ 1.48 or for $600 I can have
it with 1st @ 2.75 and 2nd @ 1.57.
Another thing I want to add is a manual/automatic valve body. There are times that starting out in second may help with tire spin.
From what I read most Caddy guys are running an 1800-2000 stall convertor. Here's the specs on the caddy motor. 420 HP@3800 547 Ft-Lbs@ 3200. The powerband is much lower than my SBC was. . A lower stall will also help with heat build up.
I'm still trying to understand all the gearing calculators out there and what the numbers mean. I have the basics down but when trying to figure out a good crawl ratio vs what will be best for drags i'm lost.
did you find a 4l80e then?
GRINCH
1/2 ton status
I'm either going to get one from BTO or PATC. After much research 
I learned that the early years had problem and some were related to the case. I didn't really want to deal with a used one since there is no good tranny folks close by that anyone would trust to build a performance one.
So for a piece of mind and warranty I'm going to fork over the $$$.
I may need a core depnding on were I buy it. Or just pay the $300- $500
I learned that the early years had problem and some were related to the case. I didn't really want to deal with a used one since there is no good tranny folks close by that anyone would trust to build a performance one. So for a piece of mind and warranty I'm going to fork over the $$$.
I may need a core depnding on were I buy it. Or just pay the $300- $500
Which STaK were you looking at?
I'm assuming a 3-speed? 1:1, 2.72:1 and 5.44:1???
Interestingly, the 2.72 is identical to an NP241 you already have. The only real advantage will be for really slow technical crawling, which seems to be the least interesting to you.
Working on calcs now... QUESTIONS:
- What is the maximum RPM you think you'll sping the Caddy motor to during sand drags?
- What do you think the total weight of your old truck was?
- What do you think the new truck will weigh?
- I've been using a 36" tire across the board for consistency in comparing numbers. How likely are you to step up to a 37" tire?
I'm assuming a 3-speed? 1:1, 2.72:1 and 5.44:1???
Interestingly, the 2.72 is identical to an NP241 you already have. The only real advantage will be for really slow technical crawling, which seems to be the least interesting to you.
Working on calcs now... QUESTIONS:
- What is the maximum RPM you think you'll sping the Caddy motor to during sand drags?
- What do you think the total weight of your old truck was?
- What do you think the new truck will weigh?
- I've been using a 36" tire across the board for consistency in comparing numbers. How likely are you to step up to a 37" tire?
GRINCH
1/2 ton status
Which STaK were you looking at?
I'm assuming a 3-speed? 1:1, 2.72:1 and 5.44:1???
Yes, but these are thier current options.
5.44:1, 3.05:1, and 1:1
4.33:1, 2.43:1, and 1:1
3.75:1, 2.10:1, and 1:1
I thought the 2.43 and 4.33 and 1.1 would work well.. But what do I know
Interestingly, the 2.72 is identical to an NP241 you already have. The only real advantage will be for really slow technical crawling, which seems to be the least interesting to you.
It may help in the snow!!!
Working on calcs now... QUESTIONS:
Thanks
- What is the maximum RPM you think you'll sping the Caddy motor to during sand drags? Not really sure. Never dealt with a BB before. From what I read, Peak HP and TQ is around 3800. And not knowing the characteristics of the 4l80 I would say somewhere between 4&5K. I will do some reading up tomorrow and see if I can find anything. I may even call the cad 500 guys
- What do you think the total weight of your old truck was? . It was 5860 with me in it.
- What do you think the new truck will weigh? . Rough guess would be the same or more. I know the first gens weighed less but this ones gonna have a 60 cad 500 (But only 50#’s more than my sbc) But a full cage not to elaborate though. Suspension seats and of course TOPLESS!!
- I've been using a 36" tire across the board for consistency in comparing numbers. How likely are you to step up to a 37" tire? . I own both but will put what ever tire does better in the drags. I also own a set of 33 MT/R and a set of 35’s are available. But for general calcs let’s use the 36’s
Thanks
OK, you asked for it....... here are the numbers and a summary of what some of this means, along with my own observations:
First, some definitions:
Rolling Radius: The measured height from the bottom of the tire to the center of the wheel hub. Designed to account for being "aired down", though in these cases I left all calculations as 1/2 tire diameter. If you want to take an "actual" measurement I can plug it in.
Drive Wheel Torque: The torque developed at the wheel hub (through all the gear reduction in the driveline) when the engine is at peak TQ.
Wheel Thrust: The torque actually applied to the bottom of the tire, accounting for the lost leverage due to the actual radius of the tire/wheel combination (since in the offroad world we use tires with a radius larger than 12", the actual Lbs/Ft value is lower than the Drive Wheel TQ value)
g-Force: This is the amount of theoretical force that is generated to move the vehicle (assuming infinite traction exists). This uses the assumption of 5860 Lbs as the vehicle weight in all calcs)
Acceleration (ft/sec): This is an estimate (again with unlimited traction) of how quickly the truck will move at peak TQ)
Assumptions:
Look at the Wheel Thrust values and Acceleration between the original setup you ran (Column 1) and the Caddy setups (columns 2 through 5). Even with a weaker 1st Gear, you have SO much more power on tap, that you are driving right over those gears and pulling WAY harder than before....even with a stock 2.48 1st gear in the 4L80E. The extra benefit is not only are you accelerating faster than before, but you also have more top-end in 1st and 2nd gear....so your max MPH is better than stock too. Of course it becomes clear that the advantage of developing better torque in the motor is that it gets multiplied by each gearset downstream and becomes truly massive by the time it reaches the tire.
Columns 3 and 5 show the effects of using the deeper gearset in the 4L80E (2.75 1st, 1.57 2nd). Honestly, I really don't see the value of them here...normally, they'd help overcome a lack of power to help get off the line better, but lack of power isn't an issue here....all they seem to do is rob you of some top-end MPH in 1st and 2nd gear. To be fair, they do help your crawl ratio slightly though.
Re-using your 241 is going to give you a 2.72 Low Range and a crawl ratio of 55.31. That's off a bit from your stock setup where you had 68.25:1. The STaK in it's deepest range would give you a substantial improvement in crawl ratio (88.05:1) but rockcrawling seems to be a lower priority to you....so I'm not sure that the STaK is money well-spent at this moment. It's a swap you can do later on without a whole lot of drama if desired.
The majoirty of these calculations were done in High range (1:1) for the transfercase. If you ran the sand or mud drags in 4LO instead the torque effects would become massively higher (more wheelspin) and the max MPH in each gear would be cut in more than half of what you see here. Keep in mind that the numbers would change proportionally for each combination so it's not like there would be a new "winner" in 4LO that isn't already showing as a top choice in 4HI.
Take a look at the numbers in more detail and post up any new observations or questions for discussion here....
First, some definitions:
Rolling Radius: The measured height from the bottom of the tire to the center of the wheel hub. Designed to account for being "aired down", though in these cases I left all calculations as 1/2 tire diameter. If you want to take an "actual" measurement I can plug it in.
Drive Wheel Torque: The torque developed at the wheel hub (through all the gear reduction in the driveline) when the engine is at peak TQ.
Wheel Thrust: The torque actually applied to the bottom of the tire, accounting for the lost leverage due to the actual radius of the tire/wheel combination (since in the offroad world we use tires with a radius larger than 12", the actual Lbs/Ft value is lower than the Drive Wheel TQ value)
g-Force: This is the amount of theoretical force that is generated to move the vehicle (assuming infinite traction exists). This uses the assumption of 5860 Lbs as the vehicle weight in all calcs)
Acceleration (ft/sec): This is an estimate (again with unlimited traction) of how quickly the truck will move at peak TQ)
Assumptions:
- Vehicle weight is always 5860 Lbs
- Tire size is always 36"
- Max engine RPM is 5000RPM
- Crawl Ratios assume a 2:1 "stall effect" in the converter
Look at the Wheel Thrust values and Acceleration between the original setup you ran (Column 1) and the Caddy setups (columns 2 through 5). Even with a weaker 1st Gear, you have SO much more power on tap, that you are driving right over those gears and pulling WAY harder than before....even with a stock 2.48 1st gear in the 4L80E. The extra benefit is not only are you accelerating faster than before, but you also have more top-end in 1st and 2nd gear....so your max MPH is better than stock too. Of course it becomes clear that the advantage of developing better torque in the motor is that it gets multiplied by each gearset downstream and becomes truly massive by the time it reaches the tire.
Columns 3 and 5 show the effects of using the deeper gearset in the 4L80E (2.75 1st, 1.57 2nd). Honestly, I really don't see the value of them here...normally, they'd help overcome a lack of power to help get off the line better, but lack of power isn't an issue here....all they seem to do is rob you of some top-end MPH in 1st and 2nd gear. To be fair, they do help your crawl ratio slightly though.
Re-using your 241 is going to give you a 2.72 Low Range and a crawl ratio of 55.31. That's off a bit from your stock setup where you had 68.25:1. The STaK in it's deepest range would give you a substantial improvement in crawl ratio (88.05:1) but rockcrawling seems to be a lower priority to you....so I'm not sure that the STaK is money well-spent at this moment. It's a swap you can do later on without a whole lot of drama if desired.
The majoirty of these calculations were done in High range (1:1) for the transfercase. If you ran the sand or mud drags in 4LO instead the torque effects would become massively higher (more wheelspin) and the max MPH in each gear would be cut in more than half of what you see here. Keep in mind that the numbers would change proportionally for each combination so it's not like there would be a new "winner" in 4LO that isn't already showing as a top choice in 4HI.
Take a look at the numbers in more detail and post up any new observations or questions for discussion here....
Hmmmm...... 
Don't everyone speak at once!
I really hate when I'm the thread-killer.
Don't everyone speak at once!
I really hate when I'm the thread-killer.
bp71k5
3/4 ton status
I'm still reading through it since yesterday. 
GRINCH
1/2 ton status
I'm still digesting it all.. I really appreciate your help on it. There is a bunch of information in the charts. Thanks for taking time to do this.
The deeper gears in the tranny look impressive on the acceleration. Almost 2' per second faster. If I was only going to do 300 yard drags I would lean more to this change but the $600 can be spent elsewhere.
Was there a reason not to run any other gears scenario's? 4.56 's?
Also trying to get things worked out on the Cad 500 /4l80E installl. There's not much out there for Fuel Injection. The other hang up is trying to find an ECM that will handle the Fuel Injection as well as the 4l80E. I have been working with Chris at the CAD Co and Rob at Affordable FI. Were getting closer. The problem is an ECM and a TBI unit from a 454/4l80E will work but the TBI will not flow enough CFM's for the 450HP Cad. The TBI can be bored out for more flow but may not be enough.
The deeper gears in the tranny look impressive on the acceleration. Almost 2' per second faster. If I was only going to do 300 yard drags I would lean more to this change but the $600 can be spent elsewhere.
Was there a reason not to run any other gears scenario's? 4.56 's?
Also trying to get things worked out on the Cad 500 /4l80E installl. There's not much out there for Fuel Injection. The other hang up is trying to find an ECM that will handle the Fuel Injection as well as the 4l80E. I have been working with Chris at the CAD Co and Rob at Affordable FI. Were getting closer. The problem is an ECM and a TBI unit from a 454/4l80E will work but the TBI will not flow enough CFM's for the 450HP Cad. The TBI can be bored out for more flow but may not be enough.
4.56s will probably look a lot like the aftermarket 1st/2nd gearset does....except in all 4 gears. You'll start to lose the highway cruise RPMs though. New axle gears are more money.... and like you observed already, the motor is giving you a huge boost already. I think going to a 4.56 ratio might also screw up your existing lockers too...isn't the carrier break at 4.10 and down? Axle gears seem like something that you can evaluate and change later on...I don't see a rush to deal with it now.
Take a look at the Holley Commander 950 or the stuff from RetroTek Speed for EFI... they both offer systems that will support 500HP. They are both TBI-type systems that bolt on like a conventional square-bore carb would....and offer fully programmable ECUs. For the 4L80E, I keep hearing great things about the CompuShift controller and I'm almost positive that's the direction I'm headed.
Axle gears seem like something that you can evaluate and change later on...I don't see a rush to deal with it now.Take a look at the Holley Commander 950 or the stuff from RetroTek Speed for EFI... they both offer systems that will support 500HP. They are both TBI-type systems that bolt on like a conventional square-bore carb would....and offer fully programmable ECUs. For the 4L80E, I keep hearing great things about the CompuShift controller and I'm almost positive that's the direction I'm headed.
With the caddy motor you're not going to want a lot of revs set it up for 5000-5200 and call it a day.
If it were me I'd do 4l80e 241 and probably 4.56s or possibly 4.88s if bigger tires are in the future plans. I'm afraid 4.10s won't quite do it with the highish 2.48 first gear plus you have the option of overdrive if you run out of gear. In overdrive and low range you should be able to run 50 mph easy
As far as electronics for the 4l80 there are a few options. I personally would use a GM computer from a 93-95 truck, a bored 454 t-body and 454 injectors. Set the fuel pressure at around 24 psi and you'll have enough air flow for 5500 rpms and enough fuel for over 400 horsepower easy. It's pretty easy to set up on the Caddy and have complete control of spark, fuel and trans. If you don't want to use a GM throttle body then have the computer modified to run 4 injectors and go with a Holley 4 barrel t-body, I think it's overkill in your application but is still an option.
The other option (more pricy of course) is go completely aftermarket. There are dozens of options for fuel injection and a couple of trans controller options as well.
If it were me I'd do 4l80e 241 and probably 4.56s or possibly 4.88s if bigger tires are in the future plans. I'm afraid 4.10s won't quite do it with the highish 2.48 first gear plus you have the option of overdrive if you run out of gear. In overdrive and low range you should be able to run 50 mph easy
As far as electronics for the 4l80 there are a few options. I personally would use a GM computer from a 93-95 truck, a bored 454 t-body and 454 injectors. Set the fuel pressure at around 24 psi and you'll have enough air flow for 5500 rpms and enough fuel for over 400 horsepower easy. It's pretty easy to set up on the Caddy and have complete control of spark, fuel and trans. If you don't want to use a GM throttle body then have the computer modified to run 4 injectors and go with a Holley 4 barrel t-body, I think it's overkill in your application but is still an option.
The other option (more pricy of course) is go completely aftermarket. There are dozens of options for fuel injection and a couple of trans controller options as well.
I'm curious....why the preference for a 4.56 or 4.88??
Here's a modified chart with those options included to help things along.....
Interestingly, the 4.56 ratio looks almost IDENTICAL to the 4.10 ratio with the deeper 1st/2nd gearset in the first two gears if you look at the acceleration numbers....
Here's a modified chart with those options included to help things along.....
Interestingly, the 4.56 ratio looks almost IDENTICAL to the 4.10 ratio with the deeper 1st/2nd gearset in the first two gears if you look at the acceleration numbers....
I'm curious....why the preference for a 4.56 or 4.88??
You pretty much nail it in the next paragraph.
Interestingly, the 4.56 ratio looks almost IDENTICAL to the 4.10 ratio with the deeper 1st/2nd gearset in the first two gears if you look at the acceleration numbers....
The better gear ratio in first will more than offset the slightly higher cruise RPM. Looking at the numbers at 65 MPH w/4l80 the rpms go from an almost too low 1,850 with 4.10s up to about 2,050 with 4.56s and a just right 2,200 with 4.88s.
I know these cruise RPMs seem a little higher than most shoot for but IME anything under 2,000 rpm in a full bodied, lifted pig of rig that most of us have ends up being doggy at best. The torque of the big caddy will help but there is much to be gained with a little more gear ratio. In fact I'll bet the fuel milage will be as good if not better at the slightly higher revs. Just for comparison when my rig had the 400 sb, 700r4, 5.13s and 37s I had no problem pulling down 15 mpg running 70. That was with the motor turning 2550 and no top on. With a little more tuning and with a top I'm sure I could have gotten close to 17.
This all changes if the 4l80 is out of the picture. With a T400 4.10s are pretty much mandatory. 2500 at 65 plus converter slippage comes in at close to 2700. 4.56 adds another 200 rpm. yuck.
Bottom line is for 90k5s situation he needs all the ratio spread he can get and a 4l80 with a little lower axle ratio will get him real close to where he needs to be. The ratio spread of a 700r4 would be better but the caddy will make short work of one of those.
The good thing is he can run the 4.10s he has and see if it works and if not be able to figure out exactly where he needs to be using real world numbers from the mud pit (I can only guess) and only have to buy stuff once.
The one thing I'm quite sure of is the 4l80 and 241 will work well and not break the bank. In this application the 3 speed t-case is kind of a waste, that money is better spent on other go fast goodies or possibly gears for the diffs.
