89IrocZ350TPI

Is it true that the best gears for a stock TPI L98 are 3.27's, and 3.42's for a TPI that has mild bolt ons such as Exhaust/Ported Intake and Runners. Also I hear that 3.73's are bad for the TPI's powerband, and 4.11's are way overkill. I know this has been posted alot but for some reason I cannot understand the TPI's powerband. I have seen 2.77 L98's run quicker than 3.27 L98's. I don't get it.

Also do these rpm's at 60 mph look correct for the gears on an L98? [Put the car away for the winter so I cant go check]

2.77's=1650 at 60mph
3.27's=1850 at 60 mph
3.42's=2000 at 60 mph
3.73's=?
4.11's=?


Thanks.................

TMFK

My 85 z has a 700 r4 & 3.73 gears.
60 mph is 2000 rpm with converter locked.

FearThisGTA

I have run in the past with 3.73's(and plan on goin back now, I miis'em), but the car ran very well with them. With 3.73's you can rocket off of the corners, its like a sling shot.

Orr89RocZ

iTrader: (20)

a L98 with aftermarket intake/runners/injectors/chip in a firebird i saw at the track with stock converter was hittin overdrive 4th gear with 3.73 gears.

i'd say 3.27's is a great match but the 700r4 makes it kinda tough. the big gap between 1 and 2nd gear really hurts. 3.42's would be better while in second and third with the ratios of the 700r4 trans. but the big 3.06 first gear would make 1st gear pretty quick with 3.42's and its already kinda quick with the 3.27's.

with a th350, i'd say 3.42's would be a nice choice. but 3.23's or 3.27's would equally perform.

the 700r4, 3.27's seems to run fine. although i bet u can pick up precious tenths by using 3.42's cuz it will lessen that 1-2 jump and keep the rpms up for that second gear.

i'd recommend a 2400-2800rpm stall for TPI... and fully modded TPI's can go as high as 3000

89IrocZ350TPI

I bet those 3.27's are better on the highway than the 3.42's. In 1/4 time there is proably not much of a difference.

John 89 Formula

My formula originally had 2:73 gears, at 80 mph the tach was dead on 2000 in od.

I upgraded to 3:42 and it was about 70 mph at 2000 rpm ( The kick in the pants when I stepped on the gas was worth it, tho)

This was on a 355 L98 with just a 3" flowmaster exhaust.

Zepher

iTrader: (1)

3.73's were perfect for my 305TPI Auto.

1989GTATransAm

iTrader: (3)

Running 3.70's with mine. However the TPI has been modified.

D's89IROCZ

3.73's here too . Just can;t get over them first two gears . Feals like your driveing the fastest thing in the world ....but I have a 5 speed

89IrocZ350TPI

Orr89RocZ, How much easier is it to spin your tires with the new 3.27's than it was with the 2.77's? Maybe thats why some 2.77 cars beat the 3.27 L98's.

Shagwell

many times, you'll spinn easier with a steeper gear. If you have the power, your motor will be bringing the tire speed up quicker w/ higher gears(numerically lower). it all depends on your combination and power band. I know of cars that ran faster w/ 3.00's than 3.73's. But a 383 TPI(LTR set-up) w/ good heads and such makes a LOT more torque than a 355 w/ a HSR, so it's powe band was better suited for the 3.00's...
its all about the combination...

D's89IROCZ

BAM ! exactly! I have the 3.73's like I said above ...but they sure aren't optimal for the track . Just wicked lil streeet rocket.


BTW I turn 2000 rpm at 60 mph ....but with a 5 speed Thats good enough for me

CC89Formula

a 700R4 shouldnt shift into OD at WOT....

Mark 89Formula

700R4s in the high performance car/engine combos were set up to shift into OD at WOT from the factory. My Formula would when it was new. The vast majority of 700R4s in the more pedestrian applications would not though.

Tibo

iTrader: (15)

I have a 305 tpi in at the moment with a set of 3.45's. They are markedly better than the old 2.73 gears. Great for city driving. At 65 mph I see around 2,000 RPM with a 5spd. I really want a set of 3.73 gears now.

Zepher

iTrader: (1)

My 700R4 in my 88 Formula would shift to OD at WOT.
I also gained 3 mph and dropped half a second in the 1/4 mile going from 3.23 to 3.73's with the bone stock TPI.
here is a vid showing the car going to OD at WOT,
http://www.transamws6.com/video/130mph.wmv

Speedy Mike

I changed the rear end of my car from 2.73 to a 3.23, I have not changed the speedo gears yet though, my car tops out at ~95mph, yet the speedo says 115. When i change the speedo gears, will my car still top out at 95 or will it go to 115?

superGMman

Nice Music. , was the speedo corrected when that pull to 130 was made?

Speedy Mike

DUDE YOU NEED TO GET SOME GAS!! LESS THAN A 1/4 TANK!

Orr89RocZ

iTrader: (20)

its easy either way but i must say, it was finicky with the 2.77s. it either go slow off the line on launch cuz too little throttle or just spin cuz i applied too much. the 3.27's have alittle bit more play to them if u will. they do help my launch. its hard to tell the difference tho. TPI torque on street tires is just asking for spinning LOL

but i chirp second gear on shifts now alot more than before with the 2.77's

Zepher

iTrader: (1)

No, it was off by about 5mph I believe.

Orr89RocZ

iTrader: (20)

his was a rebuilt trans but with stock converter.. it was set up for shifting into od at wot

CC89Formula

ok, so maybe im wrong... ive been known to do that every now and then

VincentZ28

iTrader: (2)

To get better gas milage with 3.73's, go with a RS T-5 over the IROC T-5.
5th gear .63 for RS
5th gear .73 for IROC
5th gear .59 for RS with G-Force package
5th gear .68 for IROC with G-Force package

grover85

iTrader: (1)

I hated my 373 with my auto and tpi. I ran out of rps by then end of the track. I would hit 6000 in third and you cant shift into fourth cause it wont go.

87TPI350KID

Go wit the 3.27's. Great Gas mileage with off the line performance. The 700s first steep gear is already the "off the line multiplier" Just lower ur tire pressure to about 28 and have fun.

grover85

iTrader: (1)

SC2camaro

has anyone on here used a 2004r trans instead of the 700r4 due to the beatter gearing from 1-2 ?

MY gn has a 2004r and it just rocks with a 3.42 gear and with a 26 inch tall tire it turn about 2300 @ 70 mph



my 91 z has a 2.73 posi in it and it feels great in fisrt gear but when it shifts to second gear you will break you nose on the steering wheel it lays over so hard.


i was thinking of a 3.23-3.27 gear for it also since my old 85 5.0L TPI was geared that and it was peppy.

Orr89RocZ

iTrader: (20)

if the 1-2 gear was better, like a 3.06 first drop to 1.9x or even a 2.0x second gear, combined with 3.27's or 3.42's, a tpi car would really shine.

i believe that drop costs precious time. you have alot to gain with abit better gearing. my 60's are pretty good but the 330 and 1/8 could be better i think. some other cars and trucks with similar power but better gearing in th350 trannys and sticks run similar 60 foots but run quicker ET's in the first 1/8 which leads to better ET's in teh 1/4 while trappin less than i do. my ET's could be alot deeper into the 13s i think with a better 2nd gear ratio.

think about it.... 3.27s puts me at 30mph in first, and carries 2nd to about 60 shifting at near 5K rpms. that doesnt really seem bad but it is cuz i have such a short power band with TPI. and it does take awhile to go thru second. 2nd gear rolls at 30-35mph are slow.
third gear is the gear that lasts for ever, going from 60 to 100mph. i trap the 1/8 at 80mph.. so i'm middle 3rd gear crossing the 1/8 mile and stay that way all the way out. 3rd gear will ride out to about 115mph or close to that. thats as high as ive been in third now

SC2camaro

my old 88 LO3 had 2.73 gears with 26 in tall tires and in the 1/8 mile after you crossed the timing lights and lift up on the throttle to start shutting down the car would shift into 3rd gear.

I really think that a 2004r trans in a f-body with a 3.27-3.42 is all it needs.

the biggest problem is that redheaded stepchild trans 700r4 with is go to hell gearing.

that trans gearing makes it feel like it has got big ***** til it shifts to second then it dies out.

92zcamaroperson

iTrader: (1)

Yeah im not sure what gears I have but man i can spin so easily. Which kinda sucks because its hard to take off quickly.

89IrocZ350TPI

You have the 3.23's in your 92 L98.

Shagwell

...it all depends on the combination/intended use. For all out drag racing, you want to be turning your peak hp rpm as you go throught the traps, 1:1 in the tranny(3rd in a 700). But other combinations of power(peak and curve)/ intended RPM/ weight/trans gearing/intended use, make or brake rear gear selection.

Syn

at 80 mph my 89 5.0 in 5th is around 3500rpms, can some one give me a idea on what kinda gears i got, its in storage too

1989GTATransAm

iTrader: (3)

I forgot to add that I have my 700R4 governor set up to shift at 6000 rpm in 1st because of the big drop to 2nd. The 2-3 shift is at 5600rpm. I will have to look at my datalog again but the 1-2 shift is around 35mph and the 2-3 shift is around 70+mph. Again this is with 3.70 gears.

Shagwell

if you go to the home page on here and click on the equations, you'll find all the info you need about rpm vs speed for what gearing... - If you want the best of the best(automatic), w/ overdrive, look into a 4l80e/4l80 w/ manual valvebody...turbo 400 w/ overdrive...

ps. trans gearing for 700r is 1.1 in 3rd .70 in 4th. - For stick cars, you'll have to check in the tech data, as there are a couple options...

SC2camaro

I don't think any of these guys could justify going with a 4l80e trans or a turbo 400. Due to the fact of the power there making. a 4L80E is power hogging unit. yes i know it can live with some high power. but these guys are not making that kinda power.

I personally think a 2004r will be the best trans of choice out there if your gonna make a trans change. it has be proven that a 2004r with good internals will live well into the low 10's.

my buick is making 350RWHP and 440RWTQ and that 2004r all it has in it internally when i rebuilt it is. a harden stator 10 vane pump .521 boost valve no yo yo shift kit kevlar band with heavy duty anchor pin and red alto clutches and steels. it might dided tomorrow but it has been beast to death for 1.5 yrs and several track passes with slicks.

i have listed below is the transmission gearing for a 200-4r. notice how there is not the major change from 1-2 in the 200-4r like the 700-r4

the diffrence from 1-2 in a 200-4r is 1.173

the diffrence from 1-2 in a 700-4r is 1.434

Transmission
Model
Rear Wheel Drive:

First Second Third Fourth Reverse

THM 180C (3L30) 2.400 1.479 1.000 ----- 2.000r

4L30-E 2.400 1.479 1.000 0.723 2.000r

4L30-E Optional 2.860 1 .620 1.000 0 .723 2.000r

THM 200-4R 2.741 1.568 1.000 0.674 2.067r

THM 700-R4 (4L60) 3.059 1.625 1.000 0.696 2.294r

4L60-E 3.059 1.625 1.000 0.696 2.294r

THM 400 (3L80) 2.482 1.482 1.000 ----- 2.077r

4L80-E 2.482 1.482 1.000 0.750 2.077r

TH350 2.52 1.52 1.00 ------ NA


i got my info from www.gnttype.org under the tech info

also the 200-4r has a steeper 4th gear. so u can use a lower gear in the rear axle. the gn's use a 3.42 from the factory.

Orr89RocZ

iTrader: (20)

i agree i like mine. it just needs more power to have good 4000-5000rpm performance in second gear...

but i been running my street tires on 25-27psi on the street with LCA's/brackets, panhard bar, adjustable shocks and eibach springs and i still cant hook all that well. still gotta walk it out the hole abit. first gear is violent LOL