Eng and trans swap

[DavesGMCs]

Hey there new to this page, I have a 2005 4.8l GMC Sierra SLE 4x4 with 300k+ which I am having transmission problems it's not shifting into 3 + 4 gear, has no noise or grinding at all and fluids still nice and red. Could it be just a simple fix by replacing the shifts selinoids in the pan? Or is it the 3/4 clutch pack? I also have a 2000 5.3l GMC sierra 4x4 with low miles but a messed up frame, would I be better off to swap both the motor and trans to my 2005? If I'm able to? Lol anyways any opinions or knowledge appreciated thanks.

 

[98trck]

you said the fluid looks good has it been replaced lately
if it has been did you replace the filter too
which trans do you have , is it the six speed one
have you tried the trans in manual mode to see what happens

 

[DavesGMCs]

I just got this vehicle not to long ago, so as far as I know it hasn't been done but fluids looks fine on the dipstick. Its the 4 speed trans, the 4l60e. When I manually shift from 1st to 2nd its fine, but when I shift into third it starts acting up. Same when I put it in drive gear, you can hear it shift to third and fourth and just lags power and acts up you know what I mean kind of? You think by replacing oil and filter would that fix itself?

 

[98trck]

yaa
if some has the trans fluid changed at an oil change place
they suck the fluid out thru the dip stick tube
soo maybe it has been changed that way
and maybe the filter is in bad shape