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I go an e-mail from someone asking me about programming the shift points in the 4L60E, after a gear change - its a 1999 Firebird V6. I don't know anything about the A4 programming. Can someone advise?
....... I just purchased a T/A axle 10 bolt stocker with 3.73 richmonds and a zexel-torson locker, and i would like to know if the change in gear ratio from 3.08 to 3.73 will warrent a computer flash for shift points or just speedometer correction? I got different opinions from two friends of mine but i trust your opinion will be right. I have a 99 firebird with the 3.8 v6 auto trans......
Any assistance will be appreciated.
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94 Formula A3+1: 381ci all-forged stroker - Callies Stealth, Oliver 5.85 billet rods, BME nitrous pistons / CNC LT4 heads / Comp Cams custom solid roller / TH400+GearVendors OD/4.11's / Strange 12-bolt / 300-shot N2O / Spohn Suspension / 6-pt roll bar with integrated SFC's / full AutoMeter instrumentation / MoTeC M48 Pro engine management system / a few other odds 'n ends. 800HP/800LB-FT at the flywheel.
Speedo will need recalibrated for sure, and shift point mph will also need to be adjusted. Most of the time if you use a generic tuner to adjust everything the mph values are just scaled by the change in gear ratio including converter lockup and unlock. This does not always result in a satisfactory shift table imo.
It can be driven as it sits but it is going to drive funky, and wot shifting may be a problem (didn't do any math here just speaking from experience). Results here may differ depending on what the original gear was and what the new gear is. In general I do not recommend it at all.
Appears you prediction was right on target. He already had someone tweek the speedo, but not the shift points.
Thanks Fred. I have installed the rear end and had FSTLS1TA tune for my speedo which we have gotten right. But as the quote (from WS6T3RROR) said WOT shifting is real funky. I drove the car prior to tuning and the shift points were hard and quick but my speedo was way off. Now after the tune speedo is ok but shift points are now soft kinda like as if it was slipping a little in the shift. it kinda drags through the shift. If i am easy on it the shifts are ok but really funky at WOT. Would you run this by the other guy and see what his opinion is?
Have to scale all the mph settings in the shift tables, tcc tables, kickdown tables, etc by the change in the rear differential gearing.
Usually on tuning software that is worth using there is a wizard that will fix the speedo and scale all appropriate tables at the same time. Otherwise you can manually go in and scale all the tables but its a pain and any that are missed will cause drivability issues.
Part throttle shifts are usually commanded by mph and tps (never worked on a v6 of that year so speaking generically here). Now the factory tables are set up to shift and keep the engine where it is 'happy' and so it feels positive to the driver. With the change you have made by not scaling the tables what you get is an engine that has to rev 20% higher to meet the mph setting to command a shift, also to do this the throttle input and resulting tps position will be altered as well. Do not confuse shift feel with a proper shift point. Changing part throttle shift points by only a 3-5mph can drastically alter the feel of a shift.
Wot shifting is usually done by a mph flag (called kickdown on an lt1 not sure on yours) and an rpm flag both must be set to command a wot shift. What I usually do here in the interest of performance is to put the mph flag very low and shift based on rpm. What you see in rpm is not what you get either though it will take a few hundred rpm for the shift to happen so trial and error is the way it is there.
The tl;dr version of this is scale your stock tables by the amount you changed the rear gears for a good start (hint; the new shift mph's will be lower). Adjust the points to taste and to suit your driving style. You may have to mess with the converter lockup tables a bit to make you happy, too many variables to say what to do here although it may be 100% good just scaling it.
Thanks. He followed up with e-mail that indicated they did utilize the automatic scaling. Just didn't get the expected results. So they did some more adjusting.
Fred we did some research and retuned and got it on the money. When we did the tire/gear change we used the auto scale function assuming that it would get the shift pts right but after looking around on hp tuners forum I found that the auto scale function is not always dead on. So we went in to manual mode and made a few tweeks and all is good. Thank you (and WS6T3RROR) for your help...I am kinda glad i had a few problems being that i feel i learned alot from it.
I'll give him a link to this thread, so he can read you detailed post, in case he wants to tweek it some more.