Quick transmission question.
 

Are the transmissions on the 3400 and 3800 (N/A) the same on the 6th gen vehicles and can they be swapped without much extra complication?

Thanks

The actual tranny is the same (4T65E) however, the 3400 uses a taller gearing. I believe i've read that the 3400 uses 3.05 gearing.

I believe you need to get a 3800 N/A tranny to have it the same because all engines are matched to different gear ratios.

3400= 3.05
3500= 2.86
3800= 3.29
3800 S/C= 2.93
3900= 3.29 (but 06+ trannies are a little different than 00-05, so i'm not sure if you can swap them. Maybe if you retuned you could, but IDK)
5.3L= 3.29

So your best bet is to find a 3800 N/A tranny from a Monte, Regal, Grand Prix, or Impala. The ones from the Bonneville and Mini vans are 2.84 gear ratios.

Thanks for clearing that up Mamonte. This kind of just popped into my head when I saw one on craigslist for relatively cheap.

Though, I currently don't have to do any transmission work, but I am thinking that I might sometime soon as I've just passed around 130k. I'm starting to feel a more pronounced fumbling on downshift from time to time. If time allows, I'm going to save up enough money to go with a S/C setup with a built transmission. If it goes out before then, I'll probably just get what I can get done, done. I might also look into if more reliable remanufactured transmissions if they exist for the N/A with improved aftermarket parts. If I can find any good companies.

Thanks for your help.

ZZP and Tripleedge performance have reman trannies that have the weak points fixed when they rebuild them.

Also, have you serviced your tranny? You may want to drop the pan, and change the filter/ replace what fluid comes out with some new fluid (use Dexron VI). That could very possibly cure your thumpy down shifts if your fluid is long over due for a change.

Thanks again. I've recently dropped the pan and did a refill with dex 6 and the problem hasn't gone away so far. I might look into tripleedge, mainly because the drive wouldn't be bad to pick up one of their transmissions.