shift adjustments on 4L60?

[adam74]

have a 95 tahoe 4x4 with the 4L60 auto trans and 265/70/17 tires. was wondering if there was a way to adjust the shift points. I ask because it seems to not want to stay in od when going up slight inclines much less hills and will downshift with a very light pedal. seems like it should stay in od for longer than what it is doing. driving around town its not quite as bad and I get 11 mpg but went to deer lease last weekend which is a 3 hour trip and only got 10.5 mpg. truck is rated for close to 15 highway. it does seem to run rich which I believe is due to a 180 deg thermostat installed by previous owner. going to install a stock 195 degree tomorrow. have replaced plugs, wires, cap and rotor, egr valve and selenoid, iac, fixed vacuum leaks, new o2 sensor, new cat (which made it pass emissions finally lol). I know the trans for the most part is electronically controlled but would adjusting the tv cable possibly help? dont know if its out of adjustment or not but did read somewhere it controls shift points and not really sure how to adjust it. any info is appreciated. thanks guys

 

[lesterl]

NO TV cable on a 4l60e, Need a PROM to change shift points. Got the speedo recalibrated? Exhaust leaks near/ before O2 sensor? MAP sensor any good - definitely snoop around this dude as it will help the ECM determine shift points and calculate fuel charge. Check the Coolant Temp Sensor in the coolant neck also (ohm it out). TPS sensor could also throw a wrench in the works also, ohm it out last......

 

[adam74]

new coolant temp sensor, forget to list that. no exhaust leaks, new cat/y pipe from flowmaster. did find that the vacuum hose that goes from the heater valve to the solenoid is lil loose on the valve side. pretty possible vacuum leak due to not having a tight fit. jus kinda sits on there. will try to get that fixed tomorrow to see if that helps. map sensor is about the only thing I haven't replaced. thermostat change did make the exhaust not smell so rich though

 

[lesterl]

Maybe the stat was the trick...

 

[adam74]

Im pretty sure the stat fixed the fuel mix but havent drove it to see if it helped with the trans, seemed low on power possibility possibly causing the shifting problem. would assume it would engage the choke sense it was running so much cooler than supposed to be. definately get driven tomorrow evening and Ill let ya know.

 

[lesterl]

Stat will help, especially if you can smell the difference.... Let us know. The choke is electronic (fuel injection)

 

[lesterl]

I had been getting 16-near 18 hwy on my 95 with my flowmaster

 

[adam74]

yeah 95 is tbi with electronic choke. also have a flowmaster muffler on it dueled behind the muffler. seems to have a lil more power with the correct stat. fixed the vacuum leak also. will check my mpg this weekend to see if there is an improvement and also how it handles the 3 hour trip.

 

[lesterl]

There is NO choke on a TBI. The Fuel is injected HEAVIER durring cold crank as it is a wet intake. There is a value in the programming for this even.... FE or Fuel Enrichment is the value in the PROM IIRC.....

 

[adam74]

btw still 10.5 mpg. do have a slight exhaust leak at the donut gasket. one stud broke when replacing the y pipe and it was late at night so I drilled it out and stuck a nut and bolt through it along with the spring but guessing it wasnt a good enough fix

 

[lesterl]

Stock size tires?

Stat keeping temps right now?

How about diagnosing the MAP circuit, check to see if the vacume lines are good, for that matter how much vac do you have at idle?

EGR ok? Is it leaking?

Hows Idle?

 

[adam74]

265/70/17 tires. stat seems to keep temp close to 200 now. egr valve and selenoid are new and are ac delco brand. idle still seems to stumble at times but has gotten better. vac lines are all good except the possibility of the plastic elbow at the back of the tbi spacer between the tbi and air filter housing. the one that connects the tube from the valve cover. I have it taped up pretty good but hadnt ever found a replacement part for it. not sure how to check the map sensor but that and the tps are the only things that havent been replaced. I think I read somewhere on the 95s the tps is a part of the tbi so you had to replace the tbi/tps as a package deal. not sure on vac at idle either.

 

[lesterl]

TPS is a separate piece.

Put a vacume gauge on it and see what the vac reads.
http://easyautodiagnostics.com/gm/2.8L/map-sensor-multimeter-test-1

I would still worry about that cracked/taped line...