2007 4wd transmission left yesterday. Should have it back by the end of next week. Before it left I wanted to make sure I had my transfer case concerns or questions worked out. Some of this topic was also touched on in another thread but here it is again anyway and this time with a conclusion I think. I had a couple of options for NP205 lying around. One was a 10 spline and the other was a 27 spline. I had read up a little about the AA kit and had fully planned on going that route. Their kit is for mating a 27 spline np205 to a 32 spline 4l80e. It sounded really good but pricey, not to mention all you will need to do beyond the kit such as swapping out the output shaft in the transmission and some machining inside of the transfer case to allow for the new input shaft. After down loading the instructions I made a call to speak with one of their techs. My question for him was if your kit is basically converting a 27 spline np205 to a 32 spline np205 what would be needed if started with a 32 spline np205? He said he could sell me their adapter for $200 and some change but the adapter was not offered in their catalog as a separate piece. And that the transfer case would be a bolt on but that I would still need to change the out put shaft in the 4l80e because of length. So far so good. I know a local guy that is really into muscle cars and really wanted the case from my M20 because the part number was just what he was looking for for one of his numbers matching restorations and he just so happened to have a fairly fresh th400/np205 that he had no use for. Honestly I made that happen so fast Im not sure who made out better. I called AA again and spoke to the same tech and told him I have the 32 spline np205 and am ready to order their adapter but before I did I started asking more questions that somehow led to my new case was from an 86 one ton. He then told me his adapter was for the old style or the race track bolt pattern case. 86 and up have a small circular pattern with six bolts.
Here is what I ended up doing so far. I took both the 86 and the 07 adapters into work and did a quick layout on our CMM. Using the large OD I was able to confirm that both adapters have virtually the same six bolt pattern centered off of this same feature. For some reason the 86 adapter had a lot more meat at one end making it very difficult to eye ball a match. The only real difference was the large OD itself with the 86 being 4.870 and the 07 being 4.800. At work Im thinking reducing the 86 OD by .07 is my answer but at home where I can actually line it up with the 4l80e I can see there will be clearance issues with the transmission case and the perch area at the bottom of the 86 adapter. It also looks like the output shaft on the 4l80e may be too long. After staring at the two adapters for awhile I decided to make a spacer out of the aluminum 07 adapter. The surface that mates to the 4l80e is a little less than .500. Almost perfect to help with the clearance issues and its already a fit to the transmission. I made a few marks on it where and how I wanted it machined and brought it to friend who has equipment and abilities that I do not. Once back home I used layout dye to verify that there was enough overlap between the input and output shafts. According to AA I needed a minimum of 1.5 and I ended up with 2 2.25. I will still need to add a reluctor ring inside the 4l80e but that would have been the case no matter what direction I choose. Total cost was about $60.00 for the machining. Once all the pieces come home I can begin mock up in the truck. I know I will have to make a spacer to allow use of the stock 72 transfer case cross member.
'07 - '86
'07 - '86
