jgadlage

iTrader: (1)

Alright lets see if you guys can follow my thinking here and if there is any merit to it.

I was thinking about how to make the automatic accelerate quicker aside from doing a push button tranmission shifting mechanism. What did I come up with? A thought, it may be stupid or it may be on the mark. You guys/gals tell me what you think.

The 5 speeds accelerate faster than the AT Maximas b/c of the gears in the front differential (that and the fact that you do the shifting). Is there anyway to take the gears from the differential of the MT and replace them in the AT? I know that it isn't as easy as that and there is more stuff involved in the differential than that, but is it possible and would it work better? What is the gearing differences b/t MT and AT's? Thought just crossed my mind and had to put that out there for you all. Tell me what you think.

brubenstein

I think that you're confusing the differential and the transmission. The transmission in the five speed has a greater spread of ratios than the four speed, but still keep the gear to gear ratio difference smaller. This results in a shorter (higher numerical) first gear, for better acceleration. The closer ratios keep the engine closer to its HP peak after shifting into the next higher gear. If you wan the performance of the five speed you have to swap transmissions. Hopefully, Nissan will come out with a 5 speed auto. Just don't expect to be able to back fit it to an older car.

Daniel B. Martin

This idea does nothing to address these disadvantages of the automatic transmission...
- it weighs more than the 5-speed
- power is lost through slippage in the torque converter
- five speeds can do a better job keeping the engine in the power band than four

Jeff92se

iTrader: (82)

Brub... got it pretty much right. If you want your auto to accelerate faster, you might be able to change out the differential final drive. That would give you better in all your auto gears but at the expense of a lower high end and a fudged up speedo readings. I don't even know if it's possible as I'm not too familiar w/ the auto tranny.

Mostly the diff between autos and 5-sps in maximas is the fact that 5-sds have one more forward gears to play with.

WoodEar

I don't think tiptronic is faster than full automatic.

Daniel B. Martin

According to the '99 Maxima factory service manual the final drive ratios are:
- 3.619 (automatic)
- 3.823 (5-speed)

95greense

I wish this was a possible mod. I remember when i switched the gear ratio in my 5.0 from a 2.91 (?) to a 3.73. It was like a completely different engine. My friend is switching the ratio in his 325is and he's saying that the people who have already done it see .5 sec improvement in the 1/4. I'm not sure how much an improvement going from a 3.619 to a 3.823 would be. but i guess us autos need all the help we could get.

xHypex

iTrader: (1)

In support of 95greense I have a friend who changed out his final gear on his AT Mustang. It really did make a difference in the low end, but he lost some up high (his redline is only 5500 though). He also has a chip in his car which limited him to 120 before, and after the gear limits him to 84. Sounds like a feasible mod, even though I know nothing about our drivetrain.
-hype

Daniel B. Martin

Do the math. Going from a 2.91 to 3.73 is a 28% change. That's a lot. Going from 3.619 to 3.823 is a 6% change. Not nearly as much.

95greense

daniel, how hard or expensive do you think it would be to change gears on a max. i know it's a small change but i also remember that alot of people with stangs were going from a stock ratio to a 3.15 and still noticing a difference.
thanks

Daniel B. Martin

IF the gearset is available, then the difficulty of installing it is the same as replacing a broken differential gearset. Remove the transaxle, disassemble it, remove the original differential gears, install the new ones, reassemble the transaxle, reinstall the transaxle. I think this could be done by the advanced home mechanic in two days. The pro could do it in one day. These times are guesses.

I've never bought a Nissan differential gearset and don't know what the cost would be. You might get a price quote from your favorite dealer parts man. A guess: US$200-US$300.

If you had the tranny out anyway, that would be a good opportunity to install a performance torque converter.

As a side note, Edmund's detailed specs of the 2000 Maxima, found at http://www.edmunds.com/newcars/2000/...axima/gxe.html show that 5Gen cars have a 3.62 final drive ratio for both manual and automatic transmissions. I'm not sure that's correct, but that is what they say.

jgadlage

iTrader: (1)

95Green SE hit the nail right on the head. Just like changing out the final gear ratio's like so many 5.0's do for better acceleration. Taller gears is what I want and didn't know if it was possible to install the ones from the 5 speed into the auto (maybe ommitting the 5th gear or work with some gearing that would be a compromise b/t a 5 speeds 4th and 5th gear ratio to replace the AT's overdrive).

If the gears wouldn't switch over from the Maxima maybe a 300Z would have something that could fit. You never know. Wild thought, but hey what if it WORKED!?

Even if the AT does weigh more and the 5 speed does better at keeping the engine in a good powerband there is still merit to modifying AT's. Take mustangs again. Some of the fastest cars are AT's. Why? When you get going a lot faster, an AT will give you faster, more reliable shifts than a 5-speed. Take into consideration that you are snapping off shifts w/o having to wait to change gears (TC and VB mod) and you have one fast AT. Given the weight difference the reduction in time it takes to shift would make the AT the better choice the faster your car gets. Taller gearing would definately help out getting the AT down the 1320 faster, it's just a matter of picking the right combination of gears. Maybe a custom built tranny with custom gears would be the way to go if you couldn't swap the gears out from a 5 speed.

Yo_its_ok Nah I have my AT shfting fast enough. I want to accelerate QUICKER through taller gears. I knew that 5.0's did this but didn't know if we could swap gear ratios from one tranny to the other and have it work. Eh, may be worth looking into if it doesn't cost all that much.


[Edited by jgadlage on 02-08-2001 at 10:08 PM]

95greense

hmm...i'm not quite sure bout the terminology but i think i was talking bout the final gear ratio and not the gears in the AT. I think its called the ring and pinion. If the ring and pinion from a 5th gen would fit the 4th and it was a 3.62 i think that would be a cool mod. it would seem that it would pick up the acceleration but not make highway cruising that bad. the guy who works on my car is changing out my buddies gear in his 325is for only $150.00 and it's about the same for 5.0's so it couldn't be that much more for a max. anybody know if the gears would fit? just in case i left an e-mail with courtesy nissan for a price quote and what the ratio was. hopefully they'll get back to me.

Jeff92se

iTrader: (82)

Just a quick note. Changing the gears inside a RWD drive car like the pony car or the BMW is much, much different than doing the same in a FWD car. Reason is the "gearset" that would be in the rear differential in a RWD car is inside the transmission of the fwd car. You guys probably know this but it probably needs to be mentioned anyway.

Justin. Yup! There is a reason all serious dragsters run automatic transmissions!

95greense

ahhh....so the gears are in the tranny. sorry bout that, my first FWD car. wonder how much that complicates things? maybe i should get a labor quote from my mechanic.

Nismo87SE

The auto's are faster because they have shorter 1st gears (F-bodies and maybe mustangs) so they leave harder than the manuals. However trapspeed wise the 5spds are always quicker. Now I can tell you now unless you drop over $1k you won't get any kind of different gearing made. The only other way is to find out the final gear of other FWD nissan trannys. Given the nature of the VQ powerband a 4.0-4.11 would be the best overall gear for the auto. Where as a 4.30 would be a racing only gear. The 4.0-4.11 will have you turning around 2400rpm at 60mph where as the 5spds are 2500rpm. With a high stall convertor your car will beat a 5spd off the line and he probably won't catch you until the end of 3rd gear. I had a protorque TC in my maxima and it made a big difference in off the line power. I say if you need shorter gearing just get some extra 15" wheels and run some 205-50-15's. They will give you the same gearing as a 4.0 diff. Of course the speedo will be way off but its way off anyway so its no loss. According to C&D test of a 98 maxima se auto, it was reaching these speeds at the redline in each gear (48, 84, 130, 195). With 205/50-15's it drops to 43, 76, 117, 176). Right now its the cheapest way to get shorter gearing.

95greense

thanks for the info nismo. i was thinkin the exact same thing about the impossibility of having somebody supply aftermarket gear ratios. but daniel b. martin mentioned that the 5th gens might have come with a 3.62 compared to the 3.15 in the 4th gen autos. now i don't know if the two parts can be swapped i and i don't know about the install costs but it would be pretty cool to have some better all around pick up. i just didn't realize that the gears were in the tranny and that might mean $$$ on the install. i thought bout the tire thing to but it would be pretty cool to have better acceleration on and off the track. oh well, just bouncin round some ideas.

Daniel B. Martin

To repeat my earlier posting...

According to the '99 Maxima factory service manual the final drive ratios are:
- 3.619 (automatic)
- 3.823 (5-speed)

There is no mention of a 3.15 ratio. I imagine that Edmund's rounded 3.619 to 3.62. That's entirely legitimate.

Pmp-n8a

NISMO...what stall did you use for your protorque TC?...Ive been quoted for 300+ for the TC and a 650 charge by level 10 to install it...im still thinking of a stall

VB Mod
High Stall TC
and with the correct final drive ratio

what kind of gains would AT's be looking at?

Level 10 claims outright in their catalog that their Mustang AT's will outperform any of the manuals btw

95greense

damn....got e-mail from courtesy saying that the P/N's were different and that they don't think that it's a direct swap. Good news is that they had zero info on ratios and were guessing on the swap and i'm assuming that if the ring and pinion are different ratios they probably wouldn't have the same part numbers. How would you know whether or not the same size ring and pinion is used between the two gens? if this is possible i'd love to do this cause my mechanic charges me only 1/2 on labor.
Also, bout the torque converter upgrade, is it only an improvement in launch or is there an across the band improvement? The reason the gears sound so good is that the acceleration is increased across the board. sorry if the question seems dumb but this is my first auto.
thanks guys.

Pmp-n8a

my pride has already gone to hell...im not racing until i get a protorque tc and a ypipe with 2.5 inch catback=P

in other words...ive just been really busy the past few months=P

[Edited by Pmp-n8a on 02-10-2001 at 04:54 AM]

Nismo87SE

According to my FSM stock stall speed is around 2000-2300rpm. I believe Protorque told me depending on my engine's torque I would see around 300-800rpm more stall speed. But based by what I noticed on my tach, it reved about 300-400rpm more before the car was "moving". Before the TC my car would start moving at around 1100-1200rpm. With the TC it was around 1450-1600rpm. I didn't get to track test my TC but I know for a fact this mod alone would have put me in the 15's (slow ain't it LOL). My max is pretty wierd though, I was able to run low ET's with less trap than others. As far as I know Don is the only automagic 4th gen without n2o or supercharger running 14's all day long. I bought the TC because my rear oil seal was leaking, so the install was free . If you decide to install a TC, you Will need a tranny cooler, also you should replace your rear engine oil seal and drive axle seals. That way you won't have to pay later to replace what could have been done for free. BTW those flash stalling 3000rpm launches were so hardcore. If you were able to get the ECU do it. Before my headgasket let go I only did 2 launches with the ported heads/isky cams. My car would jump off the line and the heads/cams would keep it pulling to the rev limiter in all 3 gears.

Pmp-n8a

what TC stall is don running?
and when you mean replace...you mean with oem parts? or aftermarket(if there is?)

thanks=)