so...i'm not mental...
glad to know somebody out there wants to do the swap besides me.i've just started mine,and i'm pleased to report that the trans and x-case are in,and the rear crossmember/trans support just got bolted in this afternoon.i'll post pictures as soon as possible,likely this weekend,as work is starting it's usual spring hassel.
things to consider...my project is finally coming together after nearly a year and a half of parts gathering and research.no small task considering the parts that have been cluttering my employers shop for some time,and the effort to find them.
to start...you'll need a place to work.consider carefully,as the truck WILL be idle for longer than you plan.gather all your parts first and keep them together and labeled.
once you start,DON'T STOP...that sounds easy but it's not.you will be wondering what youve gotten into,and you will almost certainly pound your head on the wall when you forget something obvious (personnal experience).that said,on to the good stuff...
the 4l-80 is a direct bolt in to the 6.2.The 400 flex plate is a direct bolt to a 4l-80 pattern,so no flex plate or starter mods.everything fits but there are some minor issues...
the trans is about 2 inches longer than the 400;the x-case will move back that aproximate distance,so modified drive shafts will be required.
you'll need a trans dipstick from a 91' k-30 with a 6.2 and a 4l-80,only made for 1 year...very hard to find used.you'll need new trans coolant lines.(i'm fabbing mine now).you need the 4l-80 inspection cover as well...be prepared to do some trimming to fit.the bolt pattern at the back of the 4l-80 is identical to the thm-400...HOWEVER,the 4l has an indexing ring that interferes with the older adapter.if you have the older figure "8" adapter,get the adapter machined to match...not to hard,DEPENDING ON THE TRANS YOU CHOOSE.
if you choose to modify a 2-wd trans like i did,give the tailshaft housing to your machinist,and tell him/her to make the adapter the same.OR,if you can find a round bolt pattern 205,a 4wd 4l-80,and the near mythical 91 4l-80 adapter,your in business.the out put shafts are the same diam and spline count.
this is important...the output shaft on the 4l-80 has to be the correct length for whatever adapter you choose...for example,the old figure 8 needs the shaft to stickout approx 4 1/2 inches to mesh properly with the x-case.if you need to do a shaft switch THE ENTIRE TRANS MUST BE DISSASEMBLED.all out put shafts on domestic cases load from the front.the out put shafts are first in,last out.
the factory crossmember should be usable...just drill new mounting holes and your in business.(use new mount/bushings).
electronics are another big issue.i'm using a compushift controller...pricey but highly adaptable,and allows some tuning...no laptop or tach required.i haven't gotten this far yet...the stumbling block will be the throttle position sensor.getting it to work on the 6.2 will be fun.you may be able to find the independant controller from a 91 to 93 gm with the 4l-80 and a 6.2...but you'll need a tach and tps to go with.
if you have more q's post them.i'll try to respond and post updates.
