Jeremy@RPMTransmissions

iTrader: (12)

Definitely keep us posted. I would really like to know the details. As of right know we aren't aware of any way to opperate them independently.

CarsandWomen

iTrader: (19)

In a drag racing/high stress situation would that be optimal Jeremy? Being that it was desined on a CAN system Im of the opinion that it would be best to run it that way. To lift the whole harness and controllers out of a ls3/6l80 vehicle would not be very hard.

FWIW I know very little about the electronic control parts so this is more or less an outside opinion, hence me asking you haha.

poorhousenext

Note: DBW is required and LS1 is not listed.
Jeremy,

Again, I'm not that well versed in how Electronic Control transmission work, so
I'm sort of at a lost by your statement "As of right know we aren't aware of any way to operate them independently."

Can you explain "independently operate/control "? Do you mean by "Independently" use another TCM to operate/control the 6L's internal TCM independent of a GM ECM, or do you mean aftermarket ECM that can replace GM's ECM to supply inputs needed from engine, that at least probably include TPS, MAF and/or MAP and RPM.

From past post you have made on 6L threads, you talk about they need a Stand Alone controller so trans can be decouple from engine.

As best as I can tell from just going through a 4L80E install, the stand along controller for it required inputs from engine for it to work.

joecar

The problem isn't mechanical advantage...

the problem is when shifting (say in the quarter mile), the wide ratio spacing causes the engine rpm to be pulled down excessively (down outside the torque range of the cam and/or the torque converter) compared to a close ratio spacing;

close ratio spacing allows the engine rpm to drop far less, keeping the engine in higher torque range, this improves ET/TS.

poorhousenext

Joe,

Help me with this. I'm dense, so bare with me.

Are you saying that 4L65 with it 3.06 1st and 1.62 2nd gear will have less RPM drop between shift, than the 6L80/90 4.03 1st and 2.36 2nd?

Doesn't the 6L80E 2nd gear just about split the MPH at 6500 RPM in 1/2 when you compare it to the 4L65 1st to 2nd MPH spread? Doesn't that mean that rpm drop will be less with the 6L80 than the 4L65's?

Am I looking at this wrong, because 4L80E is suppose to have higher RPM drop with it's 2.48 1st and it's 1.48 2nd yet the spreads look like below. Is the 4L80 not the close ratio transmission of Electronic Automatics? Baseing this on the GM M21 close ratio compared trans to GM M20 standard ratio trans. Isn't it the lost of mechanical of the 4L80 1st to 2nd gear that causes it's greater RPM drop? Don't you have to put more hp & tq in front of it or a lower rear end gear behind it to help hold down the RPM lost?

4L80 2.48 1st - 1.48 2nd = 1.0

4L65 3.06 1st - 1.62 2nd = 1.44

6L80 4.03 1st - 2.36 2nd = 1.67

Manual Trans

GM M20 2.56 1st gear - 1.88 2nd = 0.68

GM M21 close ratio, 2.20 1st - 1.64 2nd = 0.56

6L80E
1st gear 4.03, MPH @ 6500 RPM = 41.1
2nd gear 2.36, MPH @ 6500 RPM = 70.19
3rd gear 1.53. MPH @ 6500 RPM = 108.27
4th gear 1.15, MPH @ 6500 RPM = 144.04

4L65E
1st gear 3.06, MPH @ 6500 RPM = 54.13
2nd gear 1.62, MPH @ 6500 RPM = 102.25
3rd gear 1.00, MPH @ 6500 RPM = 165.65

4L80E
1st gear 2.48, MPH @ 6500 RPM = 66.79
2nd gear 1.48, MPH @ 6500 RPM = 111.92
3rd gear 1.00, MPH @ 6500 RPM = 165.65

M21 close ratio 4 sp manual
1st gear 2.20, MPH @ 6500 RPM = 75.21
2nd gear 1.64, MPH @ 6500 RPM = 101.00
3rd gear 1.28, MPH @ 6500 RPM = 129.41
4th gear 1.00, MPH @ 6500 RPM = 165.65

M20 standard ratio 4 sp manual
1st gear 2.52, MPH @ 6500 RPM = 65.73
2nd gear 1.88, MPH @ 6500 RPM = 88.11
3rd gear 1.46, MPH @ 6500 RPM = 113.46
4th gear 1.00, MPH @ 6500 RPM = 165.65

To make the close ratio trans competive, even though it has closer splits that cause less rpm drop between shifts, don't you have to go with a Lower ratio rear end to make up for the lost of mechanical advantage to get and keep weight moving?

At the strip, you have to launch at higher RPM because of lost mechanical advantage. On the street you can't do that.

M21 close ratio 4 sp manual rear end ratio changed from 3.27 to 3.70. Look how that compares to M20 with 3.27 rear end. Mechanical advantage or close ratio

1st gear 2.20, MPH @ 6500 RPM = 66.54
2nd gear 1.64, MPH @ 6500 RPM = 89.27
3rd gear 1.28, MPH @ 6500 RPM = 114.37
4th gear 1.00, MPH @ 6500 RPM = 146.40

What you see above is what I had to do with a 1965 full body Chevy with M21 close ratio trans to make it competive with same car with M20 & 3.27 rear gear at strip and on the street. Notice how close the MPH at 6500 RPM are.

Do you have to think differently when you reverse from Higher trans gears ratios with lower rear gears, to Lower trans gear ratios with higher rear gears?

Hell if I know! Just know engine rpm will nearly be the same at same speed if you lower rear end ratio to maintain the same gearing mechanical advantage.

GM/Holden Pontaic G8 did the very same thing with 6L80 & 3.27 rear gear & 6 speed manual with 3.70 rear. The 6L80 in all test was 0.2tenths of a second faster in 1/4 mile yet had a 3.27 rear gear.

Like I said, I'm dense and now even more confused by my rambling...

RevGTO

iTrader: (12)

Shift extension. Here is where hi-stall converter really helps.

TrueBlueGTO

@Jeremy, the reason I say ask the person who drives one is bc he usually has the full picture of what was done to the car. (i.e. he knows he had it tuned by so&so, ABC built the trans, and/or he also made XYZ changes himself). If you ask either the tuner OR trans builder they only have part of the story of what's in the car and what may have led to the failure.

re: CAN and Mast. Mast Motorsports is essentially GM's operating system (OS) program in their own custom Delco ECM with their own tweaks and compatible tuning software. So rather than having to get HPTuner, EFILive, or a Tech II scan tool, you use Mast's software to tune.

With that said, as CAN (Controller Area Network) is a network, there is embedded software and programming in the GM 6L80/90 TCM that seeks data from the network it was designed for. Imagine it as a CD-RW or Flash Drive. You could just as easily wipe it clean and upload Ford or Jaguar OS into the TCM and install it in its respective vehicles ECM OS network and it will work there. Therefore anyone could develop their own unique programming language and software if they fully knew how the transmission works and how to make that software compatible with all other functions of the engine and vehicle to get smooth and reliable operation under all driving conditions and demands. But why go through all that when GM has already done it and you can use tuning software to tweak it for your needs?

Now the problem you have in simply yanking a full harness and system out of any given vehicle, is that GM has designed their vehicles with fully integrated CAN systems. SO there are tens of modules in any given vehicle, depending on the options, from seat to ABS to climate control modules. These modules all talk on the same CAN network, one way or another. So to remove these modules from the network simply because you want the engine and transmission modules, won't cut it. If the system was designed not to start bc it can't tell if the accelerator pedal is fully depressed or not, or if the seat sensor shows that no one is in the seat, the computers assume the vehicle is being hotwired or stolen...that equals not start and a host of other kill codes being triggered. If say the OnStar or instrument panel is missing, the CAN system may again assume it is in a theft situation and kill fuel injection. Every vehicle and every vehicles options configuration means a different set of programs within EACH of the tens of modules...yes...thousands of program combinations. It's the result of making new vehicles more customizable and theft resistant. GM had not concern for the enthusiast retro-fitting his late model vehicle.

TrueBlueGTO

@Poorhouse. It's not a matter of the SPEED (MPH) of the vehicle. That's more an issue of tire size and vehicle aerodynamics. It's a matter of the engine, transmission, and rear end TORQUE multiplication abilities.

The rear end is a constant ratio. Whatever gear ratio is in there is all you got. The engine is a variable ratio. It's constantly revving and depending on where it is in its RPM band determines how much torque it's producing. The trend for modern vehicles to make their power high in the RPM band, unlike the TPI and big blocks of yore, means that the rest of the drivetrain has to pick up the slack to get things moving from a stand still. That leaves us with the transmission which is a hybrid of the trans and engine in that it has FIXED-VARIABLE ratios. First gear, second gear, third gear, etc.

Traditionally, you had either a car that gave great acceleration or no top end, or the other way around. In the early days the only way to play with the balance was to mess with the rear axle ratios. 2.90's for economy. 4.11 for acceleration. 3.42's for compromise. Innovative types started making the engine offer more power across the whole RPM band so you didn't have to keep the engine in such a narrow RPM range in order to feel acceleration. Then people started playing with the transmission gear ratios themselves...but we were always stuck with 3 forward accelerating gears, O/D not withstanding. Now because GM stretched the envelope of engine power production, they had to look into other ways to offer acceleration without putting further strain on the engine...add more forward gears to the transmission.

What you want to do is take the ratio of the gear you're shifting INTO and divide it by the gear you're coming out of.

6L80/90
4.03
2.36 -- 58.56% (high) RPM Retention 41.44% RPM DROP
1.53 -- 64.83% (high) RPM Retention 35.17% RPM DROP
1.15 -- 75.16% (high) RPM Retention 24.84% RPM DROP
0.852 -- 74.09% (high) RPM Retention 25.91% RPM DROP

4l65/70
3.06
1.62 -- 52.94% (high) RPM Retention 47.06% RPM DROP
1.00 -- 61.73% (high) RPM Retention 38.27% RPM DROP

4l80/85
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP


As you can see the 4l65/70 has the absolute worst ability to keep the engines RPM's high with each shift. That means the engine has to drop to a low RPM and lug itself up to speed again. When you factor in the loss of momentum between shifts due to the transmissions design, you see why it's essential that the transmission BANG into gear to minimize that loss. That however puts a strain on the trans/clutches each bang-shift. It's also why it's more of an ideal transmission for motors that make power lower in the RPMs...a nice broad mid range torque band. Something many guys don't consider when picking their cams, transmissions, rear ratios and torque converters.

Conversely, the 4l80/85 offers the absolute best RPM carry over (or minimum RPM loss) and clutch hand off between gear shifts. However, it's first gear ratio to get the ball rolling offers the LEAST amount of torque multiplication. So in order to equate the same first gear grunt that the 4L65/70 offers you'll have to once again change your rear end ratio and/or torque converter.

Last, and hardly least, is the 6L80/90 which offers the best all around compromise. Second best rating of maintaining RPM levels, highest first gear torque multiplication, gear to gear clutch handoff, an extra stepped forward gear, AND a top gear that multiplies torque 15% greater (1.00 vs 1.15)...and depending on variation...highest torque capacity.

joecar

I hadn't done the math yet...

Ratio of 1st/2nd gear ratios:
6L80: 4.03/2.36 = 1.71
4L60E: 3.06/1.62 = 1.89
4L80E: 2.48/1.48 = 1.68

The 4L80E has the narrowest spread, the 6L80 has a slightly wider spread (but comparable to the 4L80E), the 4L60E has the widest spread.

If shifting at 6800 rpm, this is the rpm that 2nd gear will pull the engine down to (assuming no stall):
6L80: 6800/1.71 = 3975
4L60E: 6800/1.89 = 3600
4L80E: 6800/1.68 = 4050

The 4L60E has pulled the motor down significantly (needs more stall and a higher shift speed).

The 6L80 and 4L80E have a comparable 1st->2nd spread

(I admit that seeing the 4.03 first gear ratio initially made me think otherwise; most gearboxes have 2nd gear well below 2.00).

joecar

Yes, true.

CarsandWomen

iTrader: (19)

TrueBlue, that is an excellent explanation both on gear splits and CAN, I do fully understand now and for that I thank you

poorhousenext

True Blue, Joe:

Thanks for showing me how to verify what my Red neck way of using fuzzy logic was telling me about gear splits.

Thanks to all for the dialog on the 6L80/90E transmission. There is just so much misunderstanding and miss information being repeated over and over about them.

Jeremy also brought up a very important point, that everyone thinking of doing a 6L conversion should be aware of, especially if they plan on beating on it. You need to make sure you can afford to maintain it and you might not want to do it if your going to use your daily driver for the conversion. Also don't blame the transmission shop if the rebuild fails too.

Now the other 6 Speed automatic. Is the TCI 6X the close ratio automatic champion.

Sure looks like it if i did the math right...

This may be one the tuners need to think about too. Because of it's gear splits will there be a need for high line pressure used with the 4L80 and 4L65 to bang the shifts.

TCI 6X (4L80E based)
2.93
2.23 -- 76.10% (high) RPM Retention -- 23.90% RPM DROP
1.57 -- 70.40% (high) RPM Retention -- 29.60% RPM DROP
1.18 -- 75.16% (high) RPM Retention -- 24.84% RPM DROP
1.00 -- 84.745% (high) RPM Retention -- 15.255% RPM DROP
0.75 -- 75.00% (high) RPM Retention -- 25.00% RPM DROP

6L80/90
4.03
2.36 -- 58.56% (high) RPM Retention 41.44% RPM DROP
1.53 -- 64.83% (high) RPM Retention 35.17% RPM DROP
1.15 -- 75.16% (high) RPM Retention 24.84% RPM DROP
0.852 -- 74.09% (high) RPM Retention 25.91% RPM DROP


4l80/85
2.48
1.48 -- 59.68% (high) RPM Retention 40.32% RPM DROP
1.00 -- 67.57% (high) RPM Retention 32.43% RPM DROP

PS: I have one of each, so I have as they say, "Skin in the Game"....

TrueBlueGTO

My pleasure. Glad I could finally offer something back to the board after years of it helping me with my various issues and projects.

I would love to see a transmission comparo of those three. If you really want to pull in all the options, throw in the Gear Vendor O/D unit behind a 4L70 or 80 and see how they compare.

No doubt, at this point, a built TCI 6 speed 4L80 based transmission is the best 6 speed for a racing scenario...price notwithstanding. You'd have to have low gears (numerically high) gears to launch well, which would hurt fuel economy a bit. Best of all, I believe it comes with it's own software so it really is the only standalone 6 spd auto option... as far as I know.

joecar

The TCI 6-speed has the closest ratios which allows a tighter stall.

poorhousenext

I want have a true comparison between a 6L80E and TCI 6X even though both are installed in same body style. The 6L80E is behind LS7, while the TCI 6x is behind a LS3 and it weighs minimum of 350 lbs more than the one with 6L80E. The one with 6L has a 3.07 rear end and the 6X has a 3.54 rear end. Tire size difference also of about 2.75" taller in favor of the 6x.

Model of car they are in has the worst aerodynamics of the nameplate, with bad front end design that creates tremendous front end lift on top of the 4' x 8' sheet of plywood aerodynamics.

The TCI 6X does come with it's on tuning software.

Both are really novelty builds, the 6L80 is a straight line car and stalled at 3000 rpm for grocery getting, while the 6X is built more for Pro Turning events with 4.0" wider trac on rear and 1.5" wider trac on front and stalled at close to a stock converter's stall at 2500 rpm.

Hope to finally get both on the road by summer if not sooner.

IF you take out the paddle shifters, the cost of 6X conversion will match that of built 4L80E conversion. You could find the 6x with paddles for just under $5400.00 dollars if you shop around. You can make your on two momentary contact switch setup to manual shift it if you want to avoid cost of paddles.

TrueBlueGTO

I stumbled across this in my flash drive from when I was first starting the research of if a 6L80 conversion is worth the time and effort and thought I's share. It makes me have to post an addendum to my previous statement.

If you're on a budget or dealing with limited power, then the 6L80 is the bang for the buck choice. If money is no object and you have all the TQ in the world, THEN TCI 4L80.

poorhousenext

As Forrest Gump said, "I'm not a SMART man." Explain what this chart is about so I can make more sense out of what its trying to tell me, and what all the fixed inputs are. I can see TQ was fixed in first example, while in 2nd example TQ was a variable for the A4's so Average (non OD) results equaled that of a 6L80E at 400 Ft Pounds of TQ.

What if anything would happen to your conclusion if you were to add into the mix, TCI's 6X (6 sp 4L80E based transmission) 1st-5th gear ratios?

Bang for the Buck can turn out out to be very limiting. I increased the Bang like most will want to do like that done in the 2nd example with the A4 transmissions, so I've gone down the "Best Bang for the Buck" road already with either 6L
80E or 90E.

I put BANG in the engine compartment that exceeded GM's recommended TQ limit of either a 6L80E or 90E. The car with it will not see any transmission abuse, so Bang for the Buck turned out to be very limiting.

I think any performance Bucks saved will probably go "BANG" to about the tune of double or triple any performance savings unless people limit their Bang and abuse applied... Fun factor Bang....Limited too...

On second 6 speed car I've tried to build for the Bang I may are may not want to, or can afford to add later on. Drive-line is stronger with Transmission rated to hold at least 850 HP. Limited Lifetime Warranty on transmission if it goes bang...

I updated drive-line with stronger rear end than car came with and selected compromise performance/mileage rear end gearing that I thought would give me the best Performance and Mileage BANG for the Buck for each transmission so I don't have cost of doing that at a later date, like some will need to do. 6L80E has 3.07 rear gearing and TCI 6X has 3.54 rear gearing.

slow67

iTrader: (2)

Problem with that is, the gearset they use for the TCI setup is only good for probably 750-800hp. Also the TCI 6 speed 4L80 doesn't have engine braking. If you have more than that, I'd go with the stock 4L80E/Th400 gearset, which is proven to 1500+hp. On top of that, when you get to that HP level, good luck hooking a numerically high gear ratio.

TrueBlueGTO

Poorhouse...I didn't want to get into any non-sponsor issues.

The reason I came up with that spreadsheet was to simply simulate/theorize how a simple transmission swap would alter the performance of a vehicle, given ALL other variables being the same....that hypothetical transmission comparo I referred to earlier.

Therefore the formulations are straightforward.
1) Take the engine Flywheel torque in the first column (e.g. 400)

2) Multiply that by the first gear ratio of the transmission...that gives your torque output at the driveshaft. (e.g. 400 x 3.06 = 1224)

3) Multiply that product by the final drive axle ratio...you have torque output at the wheel (obviously wheel/tire diameter variable notwithstanding). The 15% percent torque loss factor is added reference for those who think in wheel power rather than crank. I never bothered to do and show the calculations from this. (e.g. 1224 x 4.10 = 5018.4)

4) Repeat steps for next gear.

One can then clearly see that given the same final drive ratio in the axle and the same engine (output), the 6L80/90 twins produce more torque in each forward gear, at the wheel, than any other transmission. Torque wins races! As you only use the non-overdrive forward gears in racing, I then took the average of all the forward non-overdrive gears' total torque output. Voila...as was no surprise, the 6L80/90 twins still put out more torque across the board. I know I wouldn't mind an extra 300-2500 lb/ft of torque!!

The lower comparison chart mathematically explains how you would need to increase the power of your engine with another transmission in order to match the torque multiplication from a simple 6L80/90 transmission swap.

A TCI 6x 4L80 still falls in line with the stock 4L80 because the main ratios do not change. The extra 'split' gears may keep the engine within a narrower powerband, so the engine pulls better than a built 4L80, but each gear (and overall average) torque multiplication is still the lowest of the bunch.

Personally I prefer to get the most performance for the least amount of money...not just initial outlay, but overall. So I'd rather have a nice mild, hardly-working 400 TQ motor than deal with the building and tuning nightmares and expense of a H/C, juiced, or blown motor that will inevitably lead me to have to get a new transmission anyhow, let alone, rear end, suspension, tires, etc. This is particularly true when you keep in mind that changes to gear ratios proportionately alter the ENTIRE torque curve of an engine (i.e. +/- 10% at the bottom, middle, and top of the RPM band). Where as any engine modification is going to change a specific RPM range of power output. That is where guys tend to come into problems with your torque converter selections.

A stock 6L80 out of a junkyard can live behind 400tq all day, everyday. A stock 4L70 can't even survive behind a Trailblazer SS's stock 390tq, so no way no how is it going to last behind 475tq! And I'd LOVE to see a stock 4L80 live behind a 540 torque motor. A stock 6L90 can live behind 500tq all day every day. So imagine how much power the 4L70/80 would have to hold up to in order to match the 6L90's combined torque output. ...bang for the buck, my friend...bang for the buck!

TrueBlueGTO

Ahhh....did not know that...good to know!