Transmission Swap Tech

Practically any transmission GM produced will fit in your Malibu.   I will cover the more popular automatic transmission swaps (manual is covered in another tech topic).  First, let's start with a table showing the dimensions of the most common automatic transmissions.


Transmission Width at Bellhousing Overall Length Front Edge to Mount Pad
Powerglide 19"
25 23/64"
27 9/16"
20 9/16"
20 9/16"
Turbo 350 19 1/8"
19 1/8"
27 11/16"
30 11/16"
20 3/8"
20 3/8"
Turbo 400 20"
28 3/8"
33 27/32"
38 1/8"
26 15/16"
26 15/16"
26 15/16"
2004R 19 1/8" 27 11/16" 27"
700R4 20" 30 3/4" 22 1/2"
Vette 700R4 20" 29 7/8" 22 1/2"


TH350, Powerglide, Saginaw and Muncie

All of these use the stock TH350 crossmember and the stock length driveshaft.  


TH400 or 2004R
At first, I thought this was an easy swap.  I read an article that said you can get the crossmember from any g-body equipped with a 2004R and it will bolt right up to the TH400.  Well, that is partially true.  IF you have a 84 OR LATER G-body, it will work.  But, the 78-83 G-bodies never came with the 2004R.  The frame rail crossmember mounts are different from the latter year models.  The latter year G-bodies frame mount locations that extend further back (toward the rear of the car).  Since the 78-83 models do not have these, you will not be able to use the factory crossmember (unless you make the frame extension piece).  Other options are to either get a crossmember from G-Force Performance, get a "universal" crossmember, modify/fabricate your own, or make a frame extension piece and use the stock TH350 crossmember.   I modified mine by removing the mount pad from the front side of the crossmember, then using 1/4" thick steel plate, welding it to the back side of the crossmember.   I then drilled an elongated hole for the transmission mount bolt to go through.   Not too difficult to do yourself if you have access to a welder.  Otherwise, you will need to get someone to do this.  The TH350 driveshaft will either need to be shortened, or you can use a stock one from a later model G-body that had a 2004R transmission.  Remember, you will have to use the yoke from the TH400 on the new driveshaft.   



Go to this site for all the details: 


T5 - 5 speed swap

Check out these links for information on swapping a T5 into your Malibu/A-Gbody:
Installing a T5 Transmission  into a 78-88 A/G Body by Marc Hichens
Installing a T5 Transmission  into the Monte Carlo SS by J. Matthew Daugher


T56 - 6 speed swap

Check out John's excellent site where he swapped a LS1 and T56 into his Monte SS: 


DriveShaft Issues
If you are swapping a in a different transmission for racing or to back up a more powerful engine, you may need to upgrade your driveshaft.  I got a HD driveshaft with a 3.5" diameter and 1330 series ujoints made at a local driveline shop.  You can go to Denny's Driveshafts to see EXACTLY how you need to measure for your new driveshaft.  They also explain the differences in ujoint series (sizes). 

If you see any info that is incomplete or incorrect please contact me!


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