86 IROC

iTrader: (14)

Finished up yesterday around 1pm, went very smoothly. I drove the car around and started putting miles on it yesterday afternoon. Still nice & quiet, I love it. However, I noticed my WOT 1-2 & 2-3 shifts were comming about 500 RPM sooner than w/ my original 2.73's. I used my HPP3 to correct the speedometer before even driving the car out of the garage. I ended up having to add +2 MPH on both upshifts to get it to shift at the same RPM (6000) as when it was all stock w/ the 2.73's. I did a search when I was doing my research fo rthe swap and never saw anyone mention needing to do this. Could this possibly be why some people don't see much of a gain when swapping gears?

Reguardless, car "feels" better , will be heading to the track Friday to see if I gained anything. The weather is less than ideal, but I can most likely use an online DA calaculator to kinda figure out my gains even with this much hotter weather.

Any input guys/girls? Would like to hear about your experiences/issues with this same swap. TIA

Colonel

You reduced the slippage of the converter with the new gearing. Think about it. The 'puter shifts based on MPH. At the MPH that it thinks you should be at for 6200 RPM (assuming this is the target shift point) you're really at only 5800 due to less converter slippage.


People don't see huge gains with more gearing even if they correct the shift points.

86 IROC

iTrader: (14)

Understandable, but am I going in the right direction by raising the shift points? My car w/ the 2.73's liked to shift at 6000-6100, going by the stock tach. Without any kind of adjustment to the shift points it shifted at 5400-5500 after the gear swap. It felt like the car was just starting to come alive, and then it upshifted too soon. Could that just be a delusion in my mind because I am used to it shifting higher?

LT1Fireman

On my '95 Firebird with stock 2.73s when it was switched over to 3.42s it made a huge difference in acceleration for me. I didn't test it before the switch but the seat of the pants'ometer said it was much faster.

1654ROD

iTrader: (1)

Just about ready to purchase gears for the same swap and have a couple of quick questions. Did you purchase thick gears for the series 2 carrier or change to a series
3 carrier? What brand gears did you purchase? I was advised not to use the thick gears due to excessive noise regardless of brand.

Thanks, Rod

86 IROC

iTrader: (14)

GM Motive 3 series gears, SLP take off 3 series posi. Nice and quiet rear despite the wimpy components.

RobZ

Im in the process of changing my turd 2.73's for some 3.42's know my question.Im not familiar with the 3 series and the 2 series carrier terminology.Which one would be the correct gears for my vehicle.

86 IROC

iTrader: (14)

Are they GM gears? If so, you need a ring gear spacer or a 3 series carrier. If they are aftermarket, they could be 2 or 3 series... you'll have to look up the part # on them to determine what they are.

elderon

I am making the switch also. I am curious how this turned out for you guys. I am going with 3:42's also. I have a 3500 stall converter too. What kind of gains are expected? I am expecting 2-3 tenths or so.

86 IROC

iTrader: (14)

I added a ported TB, the gears, plugs & wires, changed the fuel filter - and picked up a little over a tenth. However, the weather was much warmer than before the gears, etc. I'd say they are worth about .1 - .15 if I had to guess. The thing I like best, the car doesn't "lug" anymore. My gas mileage has remained about the same, and the car nails 2nd gear hard. It would rarely ever squeal the tires on a WOT 1-2 shift w/ the 2.73's - it will do it every time since the 3.42's, even in this heat.

Do I regret it? Not at all. The car drives so much better since the gear swap. I changed too many things at once to really validate the gears.

Tiger2o69

iTrader: (16)

i just changed from 3.23s to 3.42s and my car always chirps 1 2 shift at wot. It rarely did it with the 3.23s. My car came with 2.73s and the rear was changed to the 3.23s one wheel wonder. I kinda got screwed on that. thats why i changed it to a posi and got the gears along with it. My car shifts at like 6500 rmp and i think it may even be hitting the rev limiter because my car seems overall slower in the 1/4 althougth i can tell a diff in acceleration around 1-2 gears. The 2-3 and 3-4 is where i think its hitting the limiter. I used a gtech and i am trapping lower now.

RobZ

Do you have any tuning done to your car?