anybody have any idea which year models are interchangeable? My truck is a 98, but has low mileage for the year. Wondering if a used transmission from a newer low mileage model would swap in, or not.

I believe you will have a bellhousing and flexplate issue, though it can be done. Also you might have to modify your transmission lines.

4L60E trans are dang good transmissions, especially the '98 & '99 model yrs when GM increased the pan volume to hold more tranny fluid for better cooling and less failure.
My '98 Tahoe has over 200,000 on the original trans, but I change the fluid every 40-50k and run synthetic fluid in her.
Have you priced a rebuild of your tranny yet?

In 2004 they started putting an input speed sensor in them and they changed a bit. Probably 03 and down to 97 would work but the thing is you never know. You could get a 2003 and it had the snot beat out of it. You could get another 98 trans and it was grandfathered. Might be better to fix what you got and know.

If you are planning to keep it a while, I suggest looking at Monster Transmissions. Price is right and slightly modified for toughness.

http://www.monstertransmission.com/Mild-Reman-4L60E65E-Transmission_c_4042.html

I have priced a rebuild, and can have it completed for $850. I will also be meticulous with flushing and changing fluids on it. I was surprised to have a transmission failure at only 129k original miles on the truck. Being the 4th owner, I'm not TOO certain how well the internal fluids were cared for in the past.

sorry for delayed reply. Thanks for the feedback, all. I plan on never getting rid of the truck, but as it is my daily driver, and accidents CAN and DO happen, I've opted out of purchasing new. I'd hate to sink a ton of cash into the truck, and have someone plow into me the following month and total the truck.

Hopefully I will get it rebuilt soon. I miss my truck.

I would suspect that the fluid/filter was never changed unless you changed it. Most people don't.

Did you change the fluid before it went? I am sitting on 298,000 miles with the original fluid and tow quite a bit. Seems like they always go after someone changes the fluid.

What did the transmission do that you think it has failed? I had one that the computer lost it's mind and had to send it to GM and have it re programmed. It would not shift out of low. The speedometer also stopped working which was the key that the trans shop said led them to check the computer. Mechanically the trans was fine after only 270,000 miles.

You are by far the exception.

Last truck had 313,000 and no changes.

Ive seen enough nasty transmission fluid to know it doesn't last forever. Most people don't think to change it till they start having problems and by then its too late.

I had not changed the fluid.

incredibly loud BOOM, followed by an awful squalling/grinding noise, loss of 4th, 3rd and reverse gears altogether.

without a doubt its a mechanical failure, and not electrical... unfortunately.

How many miles are on it?