4.8 LS 2-step launch RPM suggestions?
#1
4.8 LS 2-step launch RPM suggestions?
My combination is a little odd at the moment. I have an overly tight converter spec'd for a 6.0 (winter 6.0 rebuild planned). And I'm using a spare 4.8 I had in the shop to finish out the year.
With no 2-step limiter on the transbrake I can hit 15ish lbs at 5k "ish". Takes a good 3-4 seconds to get there but once it builds to 4200 and 6-7lbs, RPM and boost climb really fast.
Attempting to get a more controllable consistent launch out of it without grenading the stock glide case/gears. Chassis is 2900lbs race weight. 3.25 gear with a 28" tire. "3400" PTC 9.5" converter.
Do you think 5k+ is too high to set the limiter? I tried dropping the limiter down to 4500, and it won't build much more than 10-11lbs unless I sit on it forever. A 10-12lb launch last week was only good for a 1.50 60'. Looking to get back in the low 1.4x-1.3x range.
With a smaller S475, 5.3, 4600 RPM, I was pulling low 1.3x 60's on 24lbs off the t-brake. The converter was really loose down low though and didn't couple hard till 90' out or so. I think that saved my trans. I'm nervous launching at big boost and RPM with this setup.
Appreciate any input.
This was a 1.34 60'.
With no 2-step limiter on the transbrake I can hit 15ish lbs at 5k "ish". Takes a good 3-4 seconds to get there but once it builds to 4200 and 6-7lbs, RPM and boost climb really fast.
Attempting to get a more controllable consistent launch out of it without grenading the stock glide case/gears. Chassis is 2900lbs race weight. 3.25 gear with a 28" tire. "3400" PTC 9.5" converter.
Do you think 5k+ is too high to set the limiter? I tried dropping the limiter down to 4500, and it won't build much more than 10-11lbs unless I sit on it forever. A 10-12lb launch last week was only good for a 1.50 60'. Looking to get back in the low 1.4x-1.3x range.
With a smaller S475, 5.3, 4600 RPM, I was pulling low 1.3x 60's on 24lbs off the t-brake. The converter was really loose down low though and didn't couple hard till 90' out or so. I think that saved my trans. I'm nervous launching at big boost and RPM with this setup.
Appreciate any input.
This was a 1.34 60'.
Last edited by Forcefed86; 09-18-2014 at 08:36 PM.
#3
Haven't tried 5k on the limiter yet. Wasn't sure if launching that high on the limiter was some kind of glide "no-no". I never see/hear of folks going that high on an LS.
I think the converter is doing odd things because it's sooo tight. I was seeing a 1500rpm drop on the shift and under 3% slippage up top last track visit.
-thanks