Went to the track on friday to try out the new gears& posi and to my surprise it showed little differnce. Ran a 13.4 at 104.5 the same as it did before the upgrade. It did feel quicker on the steet thats why I figured it would drop into the mid 12s at least. I also got the same 60ft 2.00 that I had before. My brother in law installed them for me since he is a mechanic so I now the gears were actually changed out to 3.73. I have no clue what is going on, if any body does please help.

 

what motor setup are you running?

 

I have a ZZ4 with ported heads, 770 carb, & lt4hot cam about 400hp

 

What kind of shift points are you using?

Auto or stick?

 

It has a auto 700R4 and I shift it at about 60k or sometimes 55k.

 

traction.

 

That was my first guess. But why would my 60ft time 2.00 be the same as when I had 2.73. I would think the 60 ft would be a lot higher than what it was before if it was the traction.

 

Car should feel a lot quicker going from 2.73 to 3.73.
I did a 3.23 to 3.73 upgrade and I noticed a huge difference in off the line launching. Car accelerated like a bat out of hell with the new gears.
I just recently installed a T5 which made the car much faster than with the Stock 700R4, cut half a sec in the 1/4.

 

It does feel a lot quicker than before but the time slip does not show it.

 

get some drag slicks and your 60ft time will lower a tenth or 2 and so will your e.t. but dont expect 12s, low 13s are more likely.

 

Yeah, that was my first thought.

What kind of tires are you running? Do you have any wheel hop comming of the line?

I changed from my 2.73's to 3.73's and picked up quite a bit. Changes the rpm range also.

Also what intake are you using? It it doesnt match your cam, then you might be shifting to late. (over reving ) which is bad for et's.

 

What are your rpms at 70mph? Mine are at about 24k. Is that were they should be? As far as the intake its the stock gm dual plain which should be able to handle those rpms.

 

ok, When I ran the 2.73's I wouldnt have to go into drive. I would run the 1/8 in 1st and cross the 1/4 in 2nd. I shifted at 5800 rpm. When I changed to 3.73's I couldnt do that anymore. I had to shift into drive. I ended up suffering from 2-3 shift flare up. The car wont shift into 3/Drive at WOT. I have to let out of the throttle to get it to shift.

First off, what rpm are you staging at? Is id different than before?

The 3.73's should have picked up you 60 ft times. Check for traction issues.

Try different shift points, tire pressure and staging rpms. Are you still running the stock stall converter?

The intake may only support upto 5500 or less rpm. What is the rpm range on the cam? What is the flow rate on the heads? Are you running 1.5 or 1.6 rr on the heads?

What kind of tires are you running?