4L80 and doubler

[NV Jimmy]

My 205 has vss rear output but is not being used. Which is the better way to go? The problem in low low is the ecm thinks it's going 20 mph and revs up. No problem going up hill but down is a different story. Is there any way to fix this?

 

[bigblock72]

My 205 has vss rear output but is not being used. Which is the better way to go? The problem in low low is the ecm thinks it's going 20 mph and revs up. No problem going up hill but down is a different story. Is there any way to fix this?

Where is the VSS at currently? Sounds like you have a 2wd trans with the stock output speed sensor.If so just leave it be.

Assuming that the VSS in the trans then we should be able to mess with the idle speed and fuel cut tables to get everything in line. But I'm just guessing since I don't have much info on your combination.

Please post some info on what year the motor and computer are and what style of brake booster you are using, and maybe some pictures while you're at it.

 

[NV Jimmy]

Engine is 2003 LQ9 with original ECM with 4wd 4L80e year unknown to NWF black box and 205. (ORD planitary box wasn't available yet) Brake boster is the original 91 GMC Jimmy.