My wife's 2000 LeSabre transmission has 138,000 miles and has erratic 1-2 shifts, hard shifts and sometimes feels like it dropped out of gear at a stop as it will jump into gear when the throttle is applied. This usually happens when the car is hot and outside temps are high. The fault codes are P1811 and P0102

I have located a used transmission locally on Craigslist same model and year as mine but it is a PAB version where I have a PCB version. Can I use this trans if I swap the differential? Is the torque converter the same or different?

The seller bought engine and trans combo out of a 2000 LeSabre to swap into a 2003 LeSabre and then found the electronics were different. Seller thinks it has been rebuilt but does not have personal knowledge to say for sure. He stated the torque converter is painted blue and the case is clean and painted silver as well leading him to think it may have been rebuilt. I have not seen this yet and I don't know if there is fluid in the trans. The seller is asking $300, if it has been rebuilt this might be a fair price but what can I check to verify?

Your transmission is probably fine.
Read this before you invest your time and money in replacing the tranny http://www.tripleedgeperformance.com/Harsh-Shift-P1811.html
Notice the last line in the Common Causes section of that page: Dirty MAF sensor resulting in lower commanded line pressure
For the benefit of others reading this post, your codes indicate:
P0102 is a MAF sensor low voltage
P1811 is a Maximum Adapt and Long Shift

Based on this, I suspect your MAF sensor is bad and that replacing it with a good junkyard MAF or an OE GM MAF would solve the problem, if the wiring and connection are all good.
Sometimes a cleaning with a special MAF sensor cleaner will resolve the trouble. (Other types of cleaners leave behind residue, so the problem quickly recurs or fails to resolve.)
http://troubleshootmyvehicle.com/gm/3.8L/how-to-clean-the-maf-sensor-1 has the details

hmmm... im having similar symptoms if we unplug the MAF would it 'temporarily' fix the issue or help to diagnose?

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2003 pontiac bonneville Sle with kenwood sound system. Upgraded tweeters, door speakers, deck speakers, kenwood sub and amp. Rage r20 18inch rims. Front and rear KYB shocks and struts. GXP Strut tower brace.. She's a work in progress still

Yes, it can help you to determine if the MAF is the culprit.
Unplugging the MAF causes the computer to use pre-set info instead of MAF sensor data to keep your car running.
Typically, if your car runs better with the MAF unplugged than it does with it plugged in, it means the MAF sensor has failed.
Many aftermarket MAFs seem to be poor quality, so a junkyard replacement or a new OE GM MAF is the best bet.

so just to add something (not to take the OP off topic) unplugging the MAF didnt give me any check engine codes or anything not sure if thats normal or something is messed up

_________________
2003 pontiac bonneville Sle with kenwood sound system. Upgraded tweeters, door speakers, deck speakers, kenwood sub and amp. Rage r20 18inch rims. Front and rear KYB shocks and struts. GXP Strut tower brace.. She's a work in progress still

The light will not illuminate until 2 consecutive cycles of MAF failure.
The computer also must sense that the voltage is low for a minimum of 12 seconds.

These are reasons why intermittent MAF failures may not turn on a check engine light or even show up as a trouble code.

MKMike thanks so much for cluing me in on this. I replaced my MAF with one obtained from a salvage yard ($18) and cleaned it with MAF Cleaner ($8). This was the last of July that I did this and the next day the wife drove the car to Kansas. Since then no further issues and the codes are cleared and gone. Car shifts like the day we bought it in 2006 with 32K on the ODO, very smooth now with 135K. This procedure saved me from a costly mistake on buying another used trans to replace mine and still have the same issue. Thanks again

You're very welcome!
Glad to have helped you to save a bundle and have your car running well again.

Thanks for posting back with your results. It helps us all to know which things fix what.

Just want to add this here...

My MAF failed on my 03 Bonneville... Left the car unable to idle at all, and the throttle had to be feathered to keep it running.. Unplugged it and car ran good..

I refused to use one from the parts store... I ended up ordering a Hitachi( OEM )... Have never had another issue since..

I tell people the same with the MAF sensors, You're better off with a used GM MAF than an aftermarket MAF..

Absolutely true.

Thanks for letting us know that Hitachi made the OE part.
I tend to buy Delphi parts, as many are OE but the Delphi MAF that I bought, which failed, was a not-so-cheap made in China part.
With Hitachi manufacturing them in Japan, I know which brand my next MAF will be.

Installing a shift kit will also get rid of your P1811.

_________________
-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

Your post was very timely for me, as the 2nd Delphi MAF failed on my 02 within the 12 month Delphi warranty period.
It suddenly decided that 1.89 grams per second of air were all that ever passed it---whether it was at idle or accelerating.

Just ordered a Hitachi from Amazon so I can have it arrive on Sunday.
Hopefully, the Hitachi sensor will actually do its job.

Thanks again for the heads up on Hitachi MAFs!