Kinda of a long story here but I pulled motor and trans out of my 99 fbody and installed it in a 81 fairmont wagon. I have hp tuners but not very swift at it right now. Only thing I changed was tire size and gear.

Ok fairmont is about 500 pounds lighter and I don't have ac or power steering anymore. Trans shifted perfect in the fbody but now on the 2-3 shift it slips before it shifts and sometimes bounces off the rev limiter before it shifts.

I've had the trans for about 3 years and not alot of passes on it. Dynoed about 380 and it has a yank pt4000. I did try to lower the shift mph and rpm but with no luck. Does anybody have any ideas on what I could change or try?

Thanks
Josh

 

This sounds like a combination of sensor and tune problem.
Since you have HP Tuners, learn how to use the Scanner. Check that the MAF, TPS and MAP sensors are all giving you proper values. E.g. with ignition on, engine off, make sure the TPS values go from 0% to 100% +/- 2%.
Log MPH, RPM and Trans Pressure (or PCS current) to determine why the shifts are slipping and/or hitting the rev limit.
Since the trans was working before, the slippage might be due to low line pressure caused by incorrect sensor readings.

When you changed the Tire Size and Gear, you had the option of automatically changing the trans shifts tables. Did you chose that option? If yes, the tables should be close; if not they need to be manually changed.

Think about all the things that changed:
You removed and re-installed the wiring harness.
You connected the trans cooling lines to a new radiator/cooler.
Did you hook up a different intake system and MAF location?
You made some tuning changes.

 

Ok thanks, I logged some wot runs earlier. I have a stand alone harness for the fairmont. Didn't use the factory fbody one. The maf is in a different location now than the fbody. I also used the same trans lines, cooler and fbody radiator that was on my fbody.

I did try something, no matter how much I lower the shift mph it still flares/slips at wot on the 2-3 shift. I lowered it from a 67 to 55 and still does it

How do I check trans pressure on hp tuners or can it be done?

 

With a scanner you can only log "commanded pressure". I don't have access to HP Tuners right now and don't know what the PID is called there.
To get the actual pressure you have to hook up a trans pressure gauge which is only $35 on Amazon. Search there for "transmission pressure gauge atd-5550". Unless the trans suddenly wore out, I think your line pressure is low. Likely commanded low from the PCM due to a sensor reading problem.

 

My luck it will be wore out. I've emailed rpm to see how much they charge to freshen it up but no response yet. I guess I will drop the pan tomorrow to see if any metal is in the pan