2001 silverado transmission

I have 2001 z-71 with 84,000 miles. Recently started small slip/vibration from 1-2 gear but only when taking off with about 1/4 throttle does not do this at any other time. Any ideas?

now is it a slip or a hard shift?

now is it a slip or a hard shift?
It is a slip, or it kind of feels likse it rolls into second. it does not do it all the time. just had trans flushed.

does your engine rev up before it shifts into the next gear?

no, it does not revup at all

start looking for a new transmission. changing fluid on an old transmission often flushes out dirt that allowed the tranny to operate minimally. now, with it flushed the wear shows up and it starts slipping.

The flush rule is do it early and often beginning at 20k. otherwise, don't do it till it breaks. I have seen people have better luck with flushing old tranny's if they flush it cold - must leave enough dirt and material to keep it working right.

I'd think about the new gm performance transmission:

Chevrolet’s heavy-duty parts program has shifted into overdrive with the introduction of a new 4L60 automatic transmission assembly. This sophisticated four-speed is GM’s first remanufactured, over-the-counter automatic transmission assembly for high-performance vehicles. GM Motorsports Technology Group engineer Mark McPhail put together this appealing package that's based on the 4L60 transmission ("3FFM" code) installed in ’93 Camaro Z28s. The 4L60 transmission’s steep 3.06:1 first-gear ratio produces quick off-the-line asseleration, while its 0.70:1 overdriven fourth gear and lock-up torque converter provide quiet, economical cruising. This heavy-duty Turbo Hydra-Matic transmission is assembled with premium components from GM’s parts shelves. The turbine input shaft is shot-peened to improve its durability, and the 3-4 clutch pack is upgraded with Kevlar friction material. A high-ratio (0.74:1) servo with increased surface area applies the intermediate band positively. The valve body is calibrated for 5500rpm upshifts at wide open throttle--and unlike some automatics, the high-performance 4L60 will upshift into fourth gear at full throttle. The transmission assembly includes a 298mm (11 3/4 inches) diameter torque converter that is specially designed for high-rpm operation. The converter housing is made from high-strength steel alloy. Furnace-brazed fins and a lock-up converter clutch rated to handle 400 lbs.-ft. of torque add reliability. The stall speed is approximatly 1800 rpm with a high-performance smallblock.

They are about $1650 with a one year warranty.

juma

thanks juma, but i do not think that is it, I have gone through that before with a SUB. I think it might have to do with the computer. it felt the same before and after the flush, as well it has been flushed every 20,000, slip might be the incorrect word

It seems to be the normal on all of the '99 and up Silverados. I think you will have to live with it because GM doesn't care.

Transmissions require pros for proper trouble shooting outside of only a few items a DIY can perform himself!

Spend $17 and buy a Chilton for starters, I would look closely at linkage, wiring, and most of all the (VSS) vehicle speed sensor.

My book has a very good testing procedure for the VSS there are two test's to perform.
Before you get started I would first inspect the wiring and connectors VERY closely for corrosion, loose connector, frayed wires etc etc etc.
Next I would remove the connector and CLOSELY examine the contacts for anything except shiney copper.
After doing the above inspections Drive the vehicle, if it performs normal you just stumbled across an intermittent electrical problem. Next test to perform is a continuity test of the VSS, your looking for 1000-3000 OHMS @68degf book does not provide a temperature curve!
Book indicates the sensor has a permanent magnet and generates AC voltage, starting at 0.5V while rotating the weel (non limited slip) or weel's (limited slip) by hand, and observe 1/2 volt on your meter.
If the values are outside of the envelope or intermittent, change the VSS.
If everything checks out, go visit a good tranny shop!

I had a very simular poblem as yours on a 2000 Express and it turned out to be a VSS.

Happy Hunting!

-Mike