this is a bit much to read, but im trying to start from the top and provide details. i already have an idea of what my issue might be, but want some outside opinions, im pretty frustrated with this thing. also of note, i have not been kicking the crap out of this thing, as i knew the trans was week, and i have/had a lot of driving to do.

01 silverado 2wd reg cab short bed 4.8/4l60e 212k miles
stock. only issue with trans is tc lock up at highway speeds

swapped to lq4, long tubes, mail order tune, flushed lines and factory cooler, new fluid and filter. drove good for about 1k miles, then harsh shift into 2nd, then at about 1500 miles lost 3rd gear. no faults i can see with my scanner.

now swapped in 63k mile used 4l60, converter, new trans cooler, bypassed factory. drove good for about 1200 miles, now starting to shift harsh into 2nd. no faults my scanner can see. fluid level is good, not burnt.

long version:

truck was driving pretty good, converter started having issues, wouldnt lock up on the highway.

was in process of saving parts for lq4 swap/supposedly low mileage rebuilt 4l60e out of a wreck.

found metal in oill, had to make a trip from fl to ny so decided time to put in the lq and fresh trans.

prepped engine, went to prep "new trans", found metal chunks in pan.

decided to put existing trans back in with another used converter. flushed cooler and lines, new filter and pan gasket.

put truck together, lq runs great, trans is great, converter is great, no lock up issues anymore.

drove it around for a couple days, no issues.

drive to ny from florida, about 700 miles in i go to sleep and let my friend take over. truck is driving fine at this point.

another 100 later i wake up and take over driving again. pulling out of the rest stop, thing jumps hard into second. ask my friend and she says while i was sleeping there was traffic and it started doing that. great.

fast forward a week and im driving the truck up a hill in ny, load in the bed, trans lets go in third gear. drive it to my families house in second.

stuck in ny, i really have no choice but to pick up a used trans. find one from a yard ive used in the past with good luck.

out of an 02 tahoe, 63k miles. great. tc comes with it. install this with a new cooler, bypass the factory in radiator one. new rubber hose, flush the hard lines. fresh fluid.

put trans in, everything is great. awesome again. driving back to florida, get off in georgia for gas, pull off ramp, clunks into second. check fluid at station and its good level, red, not burnt.

no light on, my scanner doesnt pull up any faults, checked cooler lines, they arent touching the headers or anything.

any ideas/insight are appreciated.

 

What did you do for a tune when you swapped the engine???

How big was the cooler you used???

 

mail order tune, ill hold off on the name for now.

the first trans had stock in rad cooler, 2nd trans has brand new stacked plate style as recommended by the performabuilt trans faq. stock cooler bypassed.

again, 2 different transmissions, 2 different coolers, fresh fluid both times, both having same issue.

since posting last night, brand new battery (came out to the 7 year old one dead this morning) swapped in known good alt. swapped known good tps.

still no faults, still no change.

truck shifts bad into second at normal throttle, and i did some more driving, under full throttle, it hit limiter in first, does not shift into second. as soon as you lift off throttle, it shifts to second, hence my voltage/tps thoughts.

 

With no Cel or codes I would bet tune related. It's hard to get a mail order tune bang on with out some live data. Everyone's driving habits are different as well as other factors that go into tuning.

 

just got back from local tuner, truck is great now.

shift point was set at 6k, rev limit at 5800, among other things.

 

Good to hear!

 

my wallets not so happy! haha

thanks for being only one to throw out some ideas.