I know this is a very generic question as it would depend on your set up, but I'm going from a 3,200 to a 4,400. The best I was doing dead hooking at the track was a 1.87 average 1.89. If you look at my dyno, It needs more verter period. I shift at 7,400.

http://73-ls1.com/63truck/new_tune_11_27.JPG


If you had to guess, what do you think the new 60's would be?


Any of you have first hand with converter swaps and what they did for your ET?

 

IF it stalls to 4400 you'll have a extra 100hp and about 20 ftlbs of torque, so I imagine your 60's would improve alot. It's tough to guess a amount of change, but if you still hooked it'd launch a good bit harder. Also your shift recovery RPM's will be higher so you'll stay in the powerband longer. Also just a suggestion but I'd shift at around 6600 rpms if I were you. On my truck which is totally different I knocked off .25 from my 60' going from the stock converter to a 3000 stall speed. Went from consistent 2.00's, to consistent 1.74-1.76's.

 

Just wondering why you say to shift at 6,600? Truck went faster and faster the higher I shifted. I've always been under the impression you want to shift after peak power. HP is falling off but, depending on shift extension, your coming back in to equal power to do it all over again.

 

It just depends on where you fall back at after the shift. I'm just guessing that your recovery rpms are around 5k, is that close? If so at 5k vs 7400rpm you have roughly 25 less hp but 120+ ft lbs of torque at 5000 compared to 7400. So, in "theory" your truck should accelerate faster from 5000 to 5800 than it does from 6600-7400.

 

Of course this is all on paper. So what actually works the best will vary.

 

7,400-5,400 on the 1-2 shift 7,400-5,500 2-3

Now I just swaped to a 30x13.50 vs the 275/60/15 but retaining the 3.73's. I did this to spray, then figure out what gear I might need. So, by my math I can keep it in second and have enough mph to go 115+

 

Usually about 300 past peak hp sometimes 500 works great. Should just fall back to torque peak or at least not past.

 

+1 2-300 is where to be, but if yours is working at 500 keep it there.

If it's a true 4400 you will be ripping it outta the hole. FWIW, I shift at 6700 and drop down to 5k shift extension and it's a 4l60e 3200 vig that acts like a 4k. I'm carrying extra ex cab *** and I went 1.801 with a little spin. Should be low 1.7 high 1.6 hookin.

 

That ignores the torque multiplication generated by the lower gear.

If torque x lower gear at 7400 is greater than torque x higher gear at 5000, it'll still be accelerating faster at 7400 in the lower gear.

So, for 7000 rpm = 310 ft-lbs and 5500 rpm = 375 ft-lbs in 3.06, 1.63, and 1.0 gear ratios,
At 7000 rpm in 1st gear 3.06x310 ft-lbs = 950 ft-lbs
At 5500 rpm in 2nd gear, 1.63x375 ft-lbs = 610 ft-lbs
Still accelerating faster in 1st at 7000 than at 5500 in 2nd.
At 7000 rpm in 2nd gear, 1.63x310 ft-lbs = 505 ft-lbs
At 5500 rpm in 3rd gear, 1.0x375 ft-lbs = 375 ft-lbs
Still accelerating faster in 2nd at 7000 than at 5500 in 3rd.

Dyno didn't go high enough for me to use 7500...

I went from a 2800 single disc lockup (call it a non-lockup for all intents and purposes) to a 3300 5-disc lockup and picked up .5 and 7 mph in my tow rig. Most of that was from eliminating slip at higher RPMs, it got about .1 to the 60' mark.

 

FMOS,

Thanks for your input. I have a 4L80E. So with that,

7,400 first = 682 vs 5,400 second = 559
7,400 second = 407 vs 5,500 second = 378


Now what about locking the verter. I should have enough gear right now (3.73)'s to go through the traps with my 30" tire in second. I think I may need to lock it with the 4,400 I have coming, the 3,200 I think would have done it unlocked though. When would be the optimal time to lock it?