Need help deciding on a transmission.

[Mudbone]

I have a 91 K5 that is new to me and I am about to upgrade the axles. (D60F and 14BFF currently with 4.56) I am familiar with the one thing leads to another with drivetrain/suspension upgrades so I want to make some long term plans so that I don't end needing to replace something twice. I plan to use a 205 T-case and need some advice on selecting an auto transmission. I will be putting this truck on the road to get to the trail so I would like to have an overdrive gear. What are my options here? After doing some searches and reading past posts here, I am considering the differences between a 700r4 or a 4L80E so I have several quesitons.
(Some other info. I will probably start with 37-38 tires. If I find that I need to go larger I can't ever see doing anything larger than a 44. If I ever need to do an engine swap I will give serious consideration to a crate fuel injection like a 350 ramjet. I will probably never go with a 203 doubler.)

1. My truck has a 350 engine and a 700r4 tranny Correct? If so, do I automatically have the K case I have read about?

2. Is it possible to put an OD gear in a stronger transmission, say a 400, or is the 700r4 and 4L80E my only choices? (I can't afford an allison and don't want the extra weight.)

3. If I put the 4L80E on there now, What type of controller will I need to run it with the stock, non-FI engine? How will that change if I later go the FI route?

4. What are the differences in mating a 205 to the 700R4 and the 4L80E? For example, Can I stick the 205 behind my 700r4 and just change the output shaft on the 700r4 and then later put it behind a 4L80E without making any changes to the 205? Will either of these require a custom adaptor? (I am under the impression that the 205 was never put behind the 700r4 in a stock setup.)

5. Do the 700r4 and the 4L80E have the same length and bolt locations? If I put the 205 behind the 700r4 now and later go to the 4L80E will I need to move the T-case crossmember or the trans crossmember?

6. Do I really want to mess with the computer trans/FI stuff or would I be better off going with a built 700r4 and if I need to do something with the engine sticking with TBI or even going to a carb?

7. I assume any small block swap will result in the transmission staying in the same place, correct? What if I go with a big block? Will that require relocating the trans and T-case?

TIA

 

[xCaliK5x]

You should have a K case IF it has never been changed before and someone put in a generic rebuild. K cases were for all 4X4's and trucks. The difference from my understanding is the case is thicker, and the aluminum flex plate cover and brace tubes from it. I hear and read mixed things about the 700R4, some people love it and say with a proper rebuild they are fine, other people hate them and say they blow up 100 feet from your driveway in something other then a stock truck. I think alot of it is WHO does the work. I need to rebuild mine, it slips in 3rd under full throttle, cold, but is fine when warm so I have been looking into it. This is what I have found.

Sorry I can't help with anything else though.

 

[obijuan]

i think the easiest thing would be to use the fitzall spacer thats in the classifieds right now to put a 27 spline 205 behind your current 700r4.

theres lots of info here mostly from scott, 4x4high, about the techpak fitzall 75q3a or something along those lines. thats definatley the wrong number! search on here, ive posted a few threads about it, for sure.
if anything avoid the new output shaft, it makes your front driveshaft hit the trans pan.

the 4l80 uses a 32 spline which is a little more difficult to find version of the 205. mating these two can get a little fancy too. thats about all i can say about the 4l80.