Hello all. I am trying to gain as much info about the 4L80e as possible. The full boat: My GS weighs about 3800 with me in it. That includes the cage and the heavier 4l80e. I have decieded to run the HGM computer harness for the 4L80e. After some research, that appears to have everything in it I want, and some more. The motor should make close 600HP flywheel on 93. Iron heads, all the good stuff, girdle, 308s cam, vacuum pump for the brakes. Starting off with 26" DOT's. Can go higher if needed. Here is the deal. The car is going to be tite with big brakes all around, new del-a lum body and chassis bushings, and the wolfcraft race stuff with double weld in anti roll bar. Adjustable uppers and lowers with spherical upper control arm bushings. I am running drag shocks and springs in the front of the car but not in the rear. Front sway bar for street use, taken off at the track. Ford 9" What I need to know. What gear ratio would be best for this rearend, and what difference will this tranny make drag racing it, opposed to the TH400. The TCI guy I talked to said I could get a 3500 stall for the 4l80, but not any higher due to the angle of the fins and the way it locks up. I figure I can drag race only using 1-2-3 and hit the traps around 6200ish. So it appears that the tranny should act slightly as a TH400 in 1-2-3 when drag racing, except the heavier converter slowing reving down a little bit. So what I need to know is what would ideal gears be, I am thinking 4:56's which would be around 2700 RPMs on the highway with 26" tires, and also, what stories do people have draging with 4l80's. Goal is to get the car close or into the 10's. Thanks in advance, Josh
Hi Josh, I checked Coan converters web site and they have a lock up converter that stalls at 4000 RPM. You may want to give them a call and talk to their tech department about it. The lock up converter has a clutch in it, and that is where the locking up takes place. It's impotant to know if you will be able to controll when the converter locks up. I know the turbo guy's lock up the converter in their 200-r4 tranny's. The lockup is significant because of converter slippage. The ability to lock up the converter means that you will have zero converter slippage which will allow you to go much faster (MPH) with the same gear at the same RPM. I believe they use the stall for launch only and then lock the converter once they reach an RPM where the locking won't bog the engine. This will allow you to use the maximum RPM of the engine as opposed to a percentage of the RPM after it is transfered through the torque converter. This equalls an awesome top end charge. So the ratios of the 4L80E are the same as the TH400. This means other than the lock up converter and the .75 overdrive,they are pretty much the same. Here is the problem. If you go with the 4.56and a 26 inch tall tire, even with the lock up converter and your max RPM is 6500 in third gear your max speed is going to be 110 MPH. This will not get you into the 11's much less the 10's. So if you crank it up to 7000 RPM you only get 118 MPH in third gear. This will get you deep into the 11's, but not into the 10's. If you change the tire size to 29.5 you can go close to 130 MPH at 6500 RPM in third gear. This will get you well into the 10's. The 29.5 inch tall tire is great for drag racing because it will get taller as tire speed increases. The same thing happens with the smaller tire, but not nearly as much. So with the 4.56 gear and the 29.5 inch tall tire it can work at the track with third gear. The problem with this is that you may end up driving it around in third gear most of the time (why have an overdrive). With a big cam if you get the engine RPM to low the engine won't make power. It can start surging on you and load up the plugs (lots of reversion at low speeds because of valve overlap). The only time you would use overdrive would be on the highway, and you would have to be going pretty fast. 70 MPH would give an engine speed of 2700 RPM which is well below the 3500 RPM wher the cam makes power. It may make enough power to pull you along at highway speeds, but it may not. I hope your heads flow some awesome numbers so you can make alot of power over 6000 RPM, otherwise you may be better off shifting at a lower RPM. I was thinking you were going to race it in overdrive, I guess not though if you are going to making lots of power up in the higher RPM range. Anyway the TH400 does not have a lock up converter so you could not get away with as much gear because you loose some MPH potential through the slipping converter.
good info All this info is great. Does anybody know if the HGM unit will allow lockup after a certain RPM like the 200r? Then I could have it lockup at 4.5K and use 4th gear, shifting around 6200. I can use 4th gear while drag racing. I wasn't sure if I should due to the overdrive issues and lockup. But I am happy to. The 4L80 I have is extremely well built specifically designed for drag setups, so it will handle a full throttle 3-4 shift. But your right, I have too much cam for the street use, and my heads flow well, but nothing to sustain 6500RPMs using third gear. So I think I will find some 29.5 tires, and run the 4.56's. I will research more about the stall converter to use. It seems now I need to rethink my cam issues? Hey JW, any input?
trans Josh check this ford trans can fit any motor .66 od any gears you want ask for Fred Brown http://www.fbperformance.com/NewSite/page.asp?get=9&t=TopR_BottomL
If you stay with the 26" tall tires and race in overdrive you can go 135+ MPH at 6000 RPM. And at 70 MPH in overdrive you would be at 3100 RPM which is much closer to the Happy range of the camshaft. With the 26" tall tire shifting at 6000 RPM the engine RPM's will look like this. shift RPM MPH 1st to 2nd 6000 to 3600 at 41 2nd to 3rd 6000 to 4050 at 68.7 3rd to 4th 6000 to 4500 at 101.8 There is a pretty big difference between the 26" and the 29.5" tall tire. Not just the overall circumfrence. The 29.5" have a lot more sidewall than the 26" therefore they will work much better at the track (sidewall flex helps traction). The 26" will work much better on the street, less sidewall means less of the floating feeling, firmer ride and better handling.
Kelly I took your advice and called coan tech. They can get me a custom built converter around 4K stall for about $1K. It comes with a 3500HP gaurentee. Before lockup with 4.56's it is about 2% slip. I like the 26" tires for the fact that once you get traction, you have less rotating weight to deal with. By the end of the track they are probably more like 26.75" tires. I need to get this thing on a dyno and see where the HP numbers are, and from there order up a converter with launch right around my peak torque. So I plan on trying the 308s cam, 26" DOT's with 4.56 gears. All this info is great for anybody who thought about a 4l80e for drag. Regards, Josh
I love my Coan converter. You will not be sorry. Money well spent. Let us know how it works when you get it to the track.
Josh, Looking at the RPM drop from 1st to 2nd gear, you may want to try locking the converter after you get through 2nd because with the converter already locked your RPM will be below the stall speed of the converter. So it may go faster say locking up at the top of second. You should try locking at different times and see how it changes things. With only 2% slip you wont see a huge difference, but locking the converter will get you another 2 MPH on the big end.
Just to put this out there. As you may have read above I am going with the HGM Compushift unit. http://www.compushift.com/ Anyways a lengthy conversation with Mike there and I now have the full details of how this thing is really going to work and control my car. All info below is related to full throttle situations. The lockup for the converter is either on or off. It does not come on slowly as GM designed it. GM did this so as you feel nothing, HGM's feels almost like a shift into 5th gear when the converter clutch locks. It initiates only at a set MPH, not RPM. You can also select the drive gears you want it to lock up in. The options for gears are either "3 and 4", "4" or "off". "Off" setting would allow you to use the tranny and converter as a normal a normal TH400 would with 4th overdrive, allowing full slip of converter. So for me to lock the converter up, I need to drive down the track and see about what MPH in third gear, related to RPM I want the converter clutch to lock. Downside, once you lock the converter, it would be locked until you are under the selected speed. You can shift it yourself with a ratchet shifter, or just throw it in Drive. Since you can program everything, I would race with it in drive, set it and forget it. The outside planetary gear on the driveshaft side as a speed sensor. Once you input tire size, car weight, and rear end gears, it will tell you vehicle speed, and also rear wheel HP. He said it was within 1% compared to a chassis dyno. It also tells you tranny fluid temp. The kit is about $1300 but after comparing it to TCI's kit, it is well worth it. I will give full user report once I get this in my car and start using it.
Really spinning it fast Is there a reason you are leaning toward such steep rear axle ratios? Then you go with the extra short tire to make the final drive extra steep. I don't have a bunch of experience with the tall rear gears but from what I have observed the BBB likes a shorter ratio to 'load' the engine up and use the torque made in the low to mid rpm range. My personal plan was to go to a 200 4r w/ a 2600 stall and a 3.08 rear gear. I will admit that the engine I was planning isn't as 'radical' in the cam and heads, but you seem to want to really spin the engine fast. I will say that I would go with the 4L80E but it does not fit in my budget. Cool project. Keep us posted. Just a thought.
more changes Actually, I am not set on 4.56's at this point. And my stall will be around 3500 maybe more dependant on the HP/Thrust numbers. I want to utilize the overdrive, while keeping the cam behaving, so I knew 4.56's would for sure help keep RPM's high in 4th gear. At this point I need to see where the engine makes its power and decide on gears. It looks like 4.10's, 4.33's or 4.56's at this point, with 4.56's being a strong runner. The car probably won't get put into 4th gear to much on the street, and if I go with a taller gear, I would just need to drive faster to get the RPM's higher, putting the engine into good operating range and keep the car from stumbling. The dyno will tell all!
Hey Josh, if you don't lock the converter while driving around at lower speeds, this will help with the possible surging problems with the cam.
Kelly - My brothers name is Kelly, my sisters name is Kyle. Anywho - why don't you tell me about what power you were making to run that 10.79 posted in your sig. You mentioned you spray, how much power do you make before the juice, and what was your ET then? Thanks Josh
Josh, The 10.79 is without nitrous. I used nitrous on my old engine. 12.75:1 compression cam TA solid cust grind. similar to the 210S with more lift. duration is fairly short 67 heads with stage 1 valves. intake 250 CFM @ .450 lift exhust 200 CFM @ .500 lift SP1 with 1050 dominator. 2" primary headers with full 3" exhaust 9" Coan converter 4400 stall. TH350 MRVB with transbrake 3.42 gear 12 bolt with mosier axles 28"x10.5" Mickey Thompson slicks car weighed 3500 pounds with me in it shifting at 6000 RPM through the traps at 5500. 1.48 60' 10.79 @ 122 MPH
very similar motor combo Kelly, my 430 big ports flow almost exactly what yours do. I however am running 10.1 compression. How much power do you estimate you make?
Josh, Horse powers numbers are tricky, there is more than one way to come up with these numbers. When you run an engine on a dyno the numbers are calculated from the flywheel. The ratings at the rear tires and flywheel can be anywhere from 75-100 HP different. The formulas that I have use elapsed time and MPH to figure HP at the rear tires. The first formula uses ET and vehicle weight to determine HP. HP=weight/(ET/5.825)^3 for my car that's HP=3500lb/(10.79/5.825)^3 which equals 550 HP at the rear tires. The second formula uses MPH and vehicle weight to determine HP. HP=[(MPH/234)^3] x weight HP=[(122/234)^3] x 3500lb which equals 496 HP at the rear tires. I believe that the MPH formula is a more accurate gauge of HP. The elapsed time formula can vary greatly depending on how well your car can 60'.
more math good info kelly!!!!!!!! do you have any other formulas that might calculate ET based on changing rear gear ratio? for example, you know your 60' with the 3.42. What would you run if you switched to 4.56's?
Sorry, no formulas for that one. The only way to know for sure is to try it. If you are trying to compare your car to mine, the things to keep in mind are that your cam is bigger and your car is heavier. Both of these things will require you to run more gear. One of my friends has a car that is similar in weight to your car and he is running the same cam. His car has a 3.73 and a 4000 stall. His heads flow a little bit better than mine. He thinks his car would run faster with a little more gear, and I think he may be right. He is running low 11's.
