Intermittent shift from 2nd to 3rd gear

[dcarlson12]

2000 Astro approx. 415,000 km

Recently was left of side on the road when the engine died.
Had it towed to my local/trusted repair shop. They ended up replacing the ignition coil.

Appeared to drive fine but thought I could hear a bit of pinging but not really sure it is/was pinging. A bit more like a continuous purring sound but not all the time; mainly during acceleration at about 60km/h

Last couple of trips it does not want to shift from 2nd up into 3rd. I can 'make it happen', at least so far, by letting off on the gas. Shifts fine from 1st to 2nd and from 3rd to 4th.

I had the transmission rebuilt about 200,000 km ago and they installed a bit of a shift kit. i.e. It would shift quite harshly from 2nd to 3rd. I could reduce the harshness by backing off on the gas when I knew I was near the shift point.

Not sure if the transmission issue is in any way related to the recent diagnosis of and replacement of the coil or just a coincidence.
I have read that perhaps the computer needs to be 're-calibrated' or ? i.e. has my driving habit of letting off on the gas near the shift point to reduce the harshness of the shift taught the computer to wait for me to do this every time or ???

If so, how does one do this? Just disconnect the ground on the battery and then ground the positive battery cable to a good ground on the engine or ??? If so, how long does it need to be grounded?

Or is it possibly a failing 2nd to 3rd solenoid failure? Haven't driven long enough to determine if it is heat related. I am in the Pacific Northwest so just normal rainy weather type ambient temperatures.

Did have the transmission 'serviced' about three years ago. It fluid appears ok and is up the full mark.

I do not have any check engine light. Have not connected my Autotap to see if any codes stored. Maybe premature post. ???

Sorry about double post. I could find the edit button so I ended up posting twice.

Thks for any all suggestions/comments.
Dwight

[Mmusicman]

Could be just a stuck valve.
Try some "Trans Tune" by Sea Foam... it solved my delayed shifting issues.
The stuff works wonders, is highly rated from a reputable company.

[WoodButcher]

What he said^^^ with a proviso-
don't overfill, you can use a vacuum pump to remove fluid from the dipstick tube if you don't want to drop the pan. Years ago I bought a vacuum brake bleeder kit and modified it for this purpose as I wanted a bigger catch bottle. I poked holes in a Gatorade bottle top and bought a 10" coil of the hard plastic ice maker line to run into the dipstick.
I used a quart of the trans tune and I got another 6 months from that transmission before it needed rebuilding.

[dcarlson12]

To Woodbutcher,
Did you leave the Trans Tune in the transmission for the next 6 months or did you drain and replace the fluid and install a new filter in the transmission after x number of miles?
Thks,
Dwight

[WoodButcher]

Left if in, got almost a year. I did drop the pan and changed the filter, added 2 quarts Lucas and topped off with atf. As I recall it was slipping a bit.
It was the following May I got the po1870 when I siphoned it out and added 2 more Lucas so I could get to work till the rebuilt trans arrived. It's my work van and the contracts don't wait.
I looked up the thread from when I swapped the trans.
viewtopic.php?f=70&t=11853

[Mmusicman]

I left the Trans Tune in mine for about a year, until I did a converter swap and fluid/filter change.

They "recommend" you change the fluid/filter after you run it a short while, but also say it's safe to leave in. If your fluid is dirty... then you shouldn't hesitate to change it out after you run the TT through it.

I've since put another bottle of Trans Tune in, and have left it in.
All seems to be well, other than a worn weak pump with almost 300K original miles.