hey if i drain my transmission to change the fluid about how much should i have to put back in?

 

As much as you took out.

I think you're going to put about 6 quarts but do it slowly so you don't overfill. Pour in about 4-4.5 quarts then start the engine and run through the gears. Then top off. repeat until fluid level is right.

 

With your mileage, I would suggest you drain and fill it twice, once now, once a wekk from now so you get more of the old ATF out of the system.
You will need probably 6 quarts of a high mileage Dextron 3 fluid on each fill. I would also suggest because of your mileage to put 1 bottle of Lucas trannt additive on your last refill to help your old tranny give you as many miles as possible.

 

k.. thanks

 

As long as you are swapping tranny's I would change the filter on the donor tranny.
No easier time then when it is out of the truck.

 

nah... not swapping the transmissions just yet... i have yet to get a definitive call on whether or not the 3.9 trans will bolt up to the 4.0... and with a 3 week old son who lives an hour and a half away, my weekends are no longer mine... so i was just changing all my fluids on the short bus, i been puttin a lot of miles on the old beast lately... my front and rear diff fluids were black, oil was black, trans fluid was reddish black, but its all fresh and new now...

 

Should you use the high milage Dextron III and a bottle of Lucas additive? Is there such a thing as too much additive?
I will be starting my flush tomorrow.

 

I am of the opinion that if you need a oil additive then you need a new oil.
That goes for ATF, motor oil, gear lube, power steering fluid...high mileage fluids are fine, but no after market additives.

 

I'm kind of the same way...I added some Lucas to both of the Diffs in the Jeep, and mixed it according to the directions in the transfer case. Boy was that a pain in the ***. I haven't added it to the crankcase of either of my cars. I don't feel comfortable enough to do that, although I do use Fram High Mileage filters with an additive that dissolves into the oil as I drive.

 

I still don't see any reason the 3.9 tranny won't bolt up behind the 4.0. As we all know they are the same engine. I can't even see where there would be computer issues but I think that is where your problem would be. Physically I think it will fit just fine.