How feasible is it to put in a 5 or 6sp auto tranny in ?

[lexicon]

HiThe sole intention is to get the engine to run at a lower RPM on the fwy, therefore, use less gas .The questions are,-what tranny is a straight fit (a tranny from another Toyota)-what mods need to be made to the ECU (computer)-does the 2005 engine (130hp) have enough torque at the lower end to drive the care at 75 mph in the low 2000 rpm range ?How feasible ?Your knowledgeable comments welcome

[lovemyraffe]

It isn't. I had the same idea a while ago. My father-in-law owns a transmission shop and I asked him about it. I wanted to change my 4 spd auto to a 5 or 6 spd. It is possible to change it from an auto to a manual, but not to just put additional gears in.

[breezd]

I think they are not asking whether they can add gears, but as to replace the trans from another vehicle with more gears into their Vibe. The idea makes sense, but I don't think that there would be any 5sp/6sp AUTO trans that would be a direct bolt up. If you want 5sp/6sp, you're gonna have to go manual.

[djb383]

Slowing the engine rpm down will take the engine out of it's best torque/power/economy rpm range. The Toyota/GM engineers have done lots of testing/calculating and have already figured out what's best with what they've got (engine/tranny). If it was as simple as slowing the rpms down, to get better mpg, they would have done it. Torque is the name of the game and little engines have very little torque.

[lexicon]

I disagree...to a certain extent.If they did put in a 6 auto speed tranny, it would-cost more -compete with the better economy vehiclesIn reality, freeway traffic in my area runs 75-80 mph, if you go slower , you get run over.I am assuming there "may" be enough torque in the lower RPM range to drive at a higher speed., but was just asking if anyone had a knowledge of possibilities.Thanks

[coldmm803]

i would think it would be possible to put in the 6 speed manual from the GT's but dont know if it would be a straight fit and you would need a different ECU. imo, you wouldn't see gains by going up to a 5 speed but a 6 speed might gain you a few mpg. not sure how much it would help lower rpm's, at 75mph with a 6 speed i would think the lowest you might see would be 2700rpm

[djb383]

Quote, originally posted by lexicon »...........freeway traffic in my area runs 75-80 mph.........There's your answer right there..........slow down, to let's say the legal speed limit, and your engine rpms will go down and your mileage will go up and that modification is free.

[joatmon]

I don't think that the amount of money saved in improved gas mileage from changing the transmission will come anywhere close to paying for the cost to buy, adapt and install a different model transmission. I think that wind resistance of the Vibe is what kills MPG at 75 mph, not gear ratio. I have found at times I'll be walking up the gears in my 5 speed, and reach to upshift out of 5th, so I can understand thinking about adding another top gear, but I wonder if the 1ZZ engine's noted lack of low end power would really be able to push a Vibe through air at 70 -80 mph with the rpms at or below 2K. Or how much more you'd have to step on the gas to get the power to keep speed in the higher gear The cheapest way to affect your gear ratio is not to swap transmisisons, but to just put on bigger diameter tires. Cheaper and more easily reversible also. Different from trasnsmission swap in that the tires will affect the gear ratio in all gears. The trick is to figure out what the difference is between the stock tires and the larger new ones, so that you can understand the effect it has on the speedometer and odometer. If you put new tires on that have 10% more circumference than stock, then your speedometer will read 10% low, and so will the odometer. That is important if you don';t want to get a speeding ticket, and also, when you compare mpg's to see what the difference is, a mile on the 10% larger tires is actually 1.1 miles.

[lexicon]

Mr djb383HiPlease re-read my post,.It clearly states that where I live, if you drive below 75 mph, you get run over.Try parts of california....Especially in orange county.It may be easy to do it where some of you live, but, not everywhere.Just the facts....

[lexicon]

Mr Joatman,Now, that is an interesting way to approach the problem.Is there a mathematician in the house ????I like your idea.....now, what are the drawbacks of bigger diameter tires other than -will they fit ?(clearance wise)-can you re-calibrate the odometer?, not mandatory, but a "plus"-you "marginally" raise the car and therefore trap more air under the car...ok, this is a stretch.-potential poorer handling because of the higher profile tire.Based on your idea of will the Vibe/Matrix be able to push the car at 75mph with the given torque at ...lets say 2500 rpm...Maybe I am missing something, but, whether you change the gears, or change the tires, arent you still putting on the same strain on the engine?If no one has the math background, I may re-post the tire ratio question on a broader forum here and elsewhere...surely we have some math folks here.....(I will go on a drive this afternoon and see what the RPM is in automatic 4th gear at 65mph vs 75mph. I think the goal will be to drop the RPM range so the engine is operating at the lower RPM while traveling at the higher speed.To be continued.......

[djb383]

Quote, originally posted by lexicon »Mr djb383HiPlease re-read my post,.It clearly states that where I live, if you drive below 75 mph, you get run over.Try parts of california....Especially in orange county.It may be easy to do it where some of you live, but, not everywhere.Just the facts....Why don't you try being a trend setter.........you might have a domino effect and others will follow. At $4.75/gal, everyone needs to slow down and stop waisting fuel.......isn't that a no brainer? Cheap fuel is gone forever, hasn't anybody noticed? Do something, I gave you my suggestion and guarantee it will work and like I said, it's free........be sure to let us know how the tranny swap works out for ya.

[DavidPIL]

Here is a tire-size calculator, if it helps any. http://www.miata.net/garage/tirecalc.htmlI sometimes wish the RPM range was a little lower in the higher gears as well. I've found myself checking to see if I was in 5th gear while driving in the 40-45mph range. and then on the highway, would really like to see the rpms when going 70 a wee bit less than the 3200rpms but I'm sure any slight incline and I'd have to down-shift.Anywho, I hope this helps someDave

[djb383]

Anyone notice, when riding a 10 speed bike, that it becomes harder to pedal in the next higher gear. Sure, the pedals are turning slower but it takes more effort to turn the pedals. Taller tires/gears will have the same effect on the Vibe..........harder for the engine to turn.

[lexicon]

Mr djbNot trying to be difficult, but, if you aint tried drivin at 65 in the slow lane when they are all going 75-80mph, ....tell you what, you are in Texas, right.....lets see...guns legal out there.Try this and tell me how this works for you....Drive in your fast lane. Lets assume its 75-80mph...stay in that lane doin 65mph and stay there, no matter if anyone is tailgating you. Report back to us on how successful you were.

[djb383]

Geez, how many wrongs (speeders) does it take to make a right. My bad for even thinking of leaving 10 minutes earlier/later to/from work and driving a little slower. What's to report back........that my mileage went up at 65 mph, less money left my wallet and $_it for brains drivers behind me waved at me with 1 finger? ROTFLMAO at those passers by.

[lexicon]

HeyIf you leave 10 minutes earlier, you still have the same issue with the other hi speed drivers......I would love to drive 65, .............just not practical where I liveone more thing....based on your signature line, you own a v8 engine and v6 engine, how does this contribute to saving gas...they are all hemissorry you other guys , didnt mean to turn this into a different kind of thread, but.... i am just addressing djb

[djb383]

At 65 mph, the V6 (5 speed) gets 30 mpg and the V8 (6 speed) gets 22 mpg......respectable numbers IMHO but I didn't know they would do that until I slowed down. Do what you gotta do, it's just my opinion that gears and tires will not improve your mpg but I could be proven wrong. However, it has been proven that reducing speed, reduces engine rpm which increases mpg. One of these days, on a Kauhlifornia freeway, you may come up behind a vehicle, or two, or even three, that are traveling slower than you.................................bet you think about this thread when it happens. Pedal to the metal and peace out bro, I'm out of here (just at a slower pace).

[joatmon]

Take break, calm down.djb is 100% correct, slowing down from 75 will save you more gas than anything you can to change the gear ratios. lexicon is unwilling to do that, nuff saidI've never lived in either place, but the impression I get out here in Maryland is that people are more likely to be shot on the highway in California than in Texas no matter how fast they are driving. http://forums.genvibe.com/zerothread?id=23292 has gear ratios, and a copy of a thread where MadBill did the math to show how gear ratios, engine RPMs, tire size, and vehcile speed are related. I offered up tire size as a cheaper alternative than swapping transmissions. I didn't intend to say that changing the overall ratio would be different on the engine by tires instead of by tranny.I don't have an auto tranny Vibe, so I can't say precisely how it behaves, but I bet when you're driving along and come to a hill, as you go up the hill, you have to step on the gas more in order to keep the same speed. If you step on the gas enough, the tranny will automatically downshift. If you change the gear ratio enough, it will have the same effect. You may need to step on the gas more in order to get enough power to keep the car going at the same speed. You may even change it enough that you'd have to give the engine enough gas to go 75 that it would downshift. I'm not sayng it will happen, but it could. Gear ratios directly link engine speed to vehicle speed (if you ignore AT slippage), but the relationship between throttle and vehicle speed depends on a lot of different factors.You might be running the engine at a slower speed, but you'll still be overcoming the same resistance, and that will take the same amount of power, so you'll have to give it more gas to keep the engine running at that lower RPM. The question is if running the engine slower with a different gear ratio is more fuel efficient. I think that given the 1ZZ engine's lack of low end torque, it's not going to help enough to justify whatever investment it would take, not even tires. And that's not factoring in additional wear on the engine from running it under a heavier load at slower speeds.

[wyatt89]

Driving different will do more than spending 1k on a tranny...fyi, at 65mph, my gt (6spd) is turning right around 3k... Getting skinnier, harder tires will do more for you than just getting larger diameter ones, your handling will suffer a bit though.

[djb383]

Thanks Joat, you da man.

[coldmm803]

Quote, originally posted by wyatt89 »fyi, at 65mph, my gt (6spd) is turning right around 3k... thats good to know...kinda. that is and isn't directly comparable to the base vibe because the 2 engines have different rpm ranges. what is redline on the GT's? if it is 8200, that means your only using 36% of the engine (3000/8200 *100). i dont remember what rpm's my base auto vibe is at 65 but at 3000rpm's (for me thats ~72mph on the speedo) i'm using 48% of the engine (3000/6200 *100).for a few months i accidentily had larger diameter tires on (misunderstood the sidewall height stuff) but i was using 215/55/16 tires and that caused my speedometer to read correct according to gps so it increased my speedo by ~2mph but affected my odometer too, and i figured out that every 1000 miles my odometer was low by 50. the pontiac dealer near me said they can't edit the ECU to account for the different tires but theres a possibility that toyota could. they also told me they would void my warranty if i kept those tires on cause they're causeing more wear and tare on the engine and rest of the car. i dont recall those tires affecting the rpm's tho, dont think the change was large enough for that

[Mavrik]

6SPD in 6th gear runs at a higher RPM then the 5spd in 5th gear going the same speed. I know this for a fact as I owned a 5spd base Vibe and drove my wife's Vibe GT 6spd enough to notice.You won't save fuel. Its a myth that 6spd transmissions mean you can always run a lower RPM. The 6spd Vibe transmission just has a really close 1 - 3 ratio compared to the 5 spd 1-2 ratio.

[KNINE]

I always wondered about that. Thanks for the info.

[lexicon]

At 65mph the automatic does 2600 RPMAt 75 mph the automatic does 3000 RPMSo, there is a 20% increase in RPM for that 10mph.So, based on the previous post, does that mean that the circumference of the tire needs to be increased by 20% to cut back on 500 RPM ?So, we need to take the circumference of the stock tire , add back 20% more inches and calculate what tire corresponds to that distance around the tire. Now, who here is good at math that can figure out what tire would need to be mounted to accomplish this task ???????If no takers, I will re-post this question on another threadNOTE: I edited this post on 6/28 to reflect the correct MPH

[djb383]

You need a tire that is 29.85" in diameter. There may be dozens of different section widths and aspect ratios in combination with a 16" rim that will yield a 29.85" diameter tire.

[joatmon]

THe math is that (RPMs /(gear ratio * final drive ratio)) * tire circumference * units conversion factors = vehicle speedWhat this means is that given a fixed tire size and gear ratio, RPMs * some constant = vehicle speed, but your numbers don't support that. Using 65 as the base, you had to increase the RPMs by 500, or 20%, but the vehicle only increased speed by 5 MPH, or 7.7% Those two percentages should be the same, but they are significantly different.That means that something isn't linear or directly proportional like it should be In an automatic tranny car, there is some slippage in the torque converter. If your numbers are accurate, then thats the only thing I can think of to explain the differences in percentages. In a manual transmission there isn't (normally) any slip, and the math works well. I guess that at 70 mph, there is more load, which makes the torque converter slip more. Either that or the tach or speedometer isn't all that accurate.It would be interesting to know how much slip there is. At some point, do a test. Cruising along at some speed, 65, 70, 75, whatever, take your foot off the gas and the RPMs should drop. Before the car starts to slow significantly, get that RPM reading, that should be one end of the slip, where the torque converter is driving the engine. Then floor it, and get the RPM reading before the car starts to accelerate . That would be the other end of the slip, the engine driving the torque converter. The diference in RPMs wil lgive you an indication of how much slip there in the auto tranny. Maybe it will be enough to explain the non-linearity you measured with 65 mph @ 2500 RPM, yet only 70 mph @ 3000 RPMHowever, if you ignore that and use math to start with the 2500 RPM@65 MPH and want to increase tire sizez so that 2500 RPMs gives you 70 MPH, then the dirfference is the difference in speed, about 7.7% The stock tire has a circumference of 78.2 inches, you'd want one 7.7% larger, about 84.2 inches. You can play with the tire size calculator at the miata site to see what percentage differences you can get with different tire sizes from the stock 205/55/16 tire sizeOr, you can use the calculator that goodvibe posted about in the tire calculator sticky in the wheels forum, it's pretty cool, does all the math for you, calculates speed vs RPM in different gears and tires sizes . It does seem to require 5 gears, the base AT has only four, so if you use this linkhttp://www.car-videos.net/tool...ulate it has the base auto tranny gears loaded, but I set 4th and 5th to the same, otherwise it imagined a higher 5th gear. The gear ratios are easy enough to change, but you can adjust the tire size there and see what the target mph is for a given RPM and tire size.http://www.sfgate.com/cgi-bin/...1.DTL is a news story of a Californian who tried out the 55 mph technique, the amount of gas saved and the hostility created among Californians

[lexicon]

Joatmon,Thanks for your thoughtful analysis.An interesting topic.(are you an auto engineer ?)A question or two.Can someone who has a manual 5 speed drive at 65 mph and at 70 mph and note the RPMs for both. I bet we are, "in real life" gonna see something similar in terms of the RPM difference.Another question. Once we assume that , lets say 1000 RPM is what it takes to get the Vibe moving, can this be factored into the overall way we are analyzing this ? I realize that the auto tranny is in slip mode for a portion of its function, but , is it actually slipping when doing a constant 65MPH and constant 70 MPH ?Thanks for your thoughts and contribution.

[joatmon]

I got these numbers with my 5 speed this morning. I took pics of the scan gauge to capture numbers. One thing to note is that the response time of the scan gauge is a lot faster for the tach than for the speed. The tach gives the scan gauge thousands of pulses per second, but the speedometer signal is much slower. If I watch the needles in the gauge, both move together very smoothly. I guess I am saying that since there is no slippage, the RPMs must be directly proportional to the speed, and there is a variance in the numbers, which I attribute to the sampling rate of the scangauge and the fact that I suck at maintaining a really steady speed at 10 to 15 mph faster than the traffic around me, so as the speed wasn't help perfectly steady, the tach changed before the mph updated. Also to note is that the tach is giving me four digits, ,while the speedometer is only giving me 2, rounding to the nearest integer. So what shows at 60 mph might acutally be 59.6 or it could be 60.4.Still, the numbers came out pretty close.If I divide the engine RPMs by the speed, for my data I get(MPH - RPM - RPM/MPH)60242040.365264740.770282740.4(it's also important to remember that the scan gauge can be adjusted to calibrate the speedometer reading. Mine is set to be close to what the needle shows, but that doesn't mean that either are absolutely accurate)For your numbers I get (MPH - RPM - RPM/MPH)65250038.570300042.8Maybe the variance in your numbers is due to torque converter slipping, maybe it is from the inherent inaccuracy of trying to put an exact number on the coarse analog gauges.

Attached files

[lexicon]

joatmonAgain, thanks for your participation.I made a mistake, my RPMs were incorrect. I will properly update them tomorrow. AT this point, it appears the 3000rpm is closer to 75mph. Will confirm tomorrowThanks

[joatmon]

That's good to know. I'd hate to think the auto tranny was losing that much coupling. Using that rpm to speed calculator, you should be seeing on the order of 61/62 at 2500 rpm, and 73/74 at 3000 rpm. or using that ratio, about 2640 RPMs at 65 mph, 3045@75Paying more attention to mine, the 1ZZ at 2500 rpm should have enough power to push the car at 75 mph, but I still wonder about the throttle position required. The premise of the thread is that changing the gear ratio to drop the RPMs at 75 mph will save gas, and I'm still not sure that will help, or help enoughWind resistance is a function of the square of the speed. While 75mph is only about 15% faster than 65 mph, the wind resistance at 75 mph is 33% more than at 65 mph. At 75 mph, the Vibe's aerodynamics make this wind resistance a factor you can't ignore. (dropping from 75 to 55 cuts a whopping 86% of the wind resistance) At lower speeds, the wind resistance isn't as significant, so running at lower RPMs will have more of an effect at 30 mph, but at 75, the resistance becomes a major factor, more significant than just the losses from running the engine faster. You can't look at just the gear ratios and assume that if you get a certain miles per gallon on the highway at 65 mph, you can get that same mpg by re-gearing to run 75 mph at the same RPM. You'll have 33% more wind resistance to overcome, which means you'll have to generate more power to compensate, which means you'll have to burn more gas to go faster, even though the RPMs are the same.I am not an automotive engineer, and I don't know the details on the 1ZZ engine performance. It may be that the engine is more efficient generating the power required to push the car at 75 mph at 3000 RPM, and re-gearing to run 75 at 2500 RPM is less efficient. I don't know how to calculate it, and it costs money to do it and measure the results. The two questions I can't answer are:1. Will changing the gear ratio reduce gas usage at 75 mph?2. If it does, will it save enough gas to be worth the cost to do it?The answer to #2 depends on how much you gas save, how much you drive, what the mod costs, and how much gas costs. My gut feeling is that it's not worth it, will cost more to do than you'll save by doing it. Unless there are other value factors, like a desire to prevent global warming by using less gas, or to reduce the country's dependence on oil imports, or other less immediate or non-ecomomic principles, but if those were important factors, you already be driving 55 If you do decide to try it, take lots of notes, try to get accurate info. If you do it and want to compare gas used before and after, it's important to eliminate as many variables as possible. How much you run the AC, how fast you go, how hard you accelerate, the before and after data has to be for the same conditions. . Sometimes just paying attention to gas used will affect driving habits enough to get better mileage. Unless the effect of the change is drastic, it's hard to know if the difference was from the mod or from a good tailwind. Or from a gas pump that shut off sooner than another one did.

[lexicon]

JoatmanHere are the stats on my 4sp Automatic base Vibeat 75 mph -engine runs at 3000 RPMat 65 mph -engine runs at approx2600 RPMSo there is a difference of 400 RPM for this 10 mph speed ...Sorry about my previous figures they were wrong.