drivetrain upgrade, not sure where to start.

[tsroark]

I currently have a Carbureted 350/400/205/4:10 14b+d44 in my 80 k20 flatbed.  Low speeds it is one heck of a truck, but after 45-50 it doesn't do so hot.  It screams like crazy to keep up at 60 and anything around 70 is very difficult.  I know it is a very heavy truck to be driving at highway speeds but it does its share of heavy lifting.  It also has a dirt cheap insurance rate and no monthly payment.  Borderline hypermiling will almost get me 8.5mpg.  I know the 4:10 gears do wonders for me, but it can and does pull out stumps that make new 1 tons cry.

I know the drivetrain is getting old and tired.  I believe the tranny was rebuilt in 90, same time the 350 replaced a 400.  So I'm thinking its time for some work.  The problem is that this truck gets me to work, I don't have another vehicle I can use while the engine is out.  And I've only got a budget of 1500 - 2k.  So I was thinking about replacing the turbo 400 with a good, working nv4500 from a 94 chevy, from the little research I've done I think the 93 or 94 will bolt up to the 205, please correct me If I'm wrong.   I like the 5 speed for a few reasons.  There are no computers or I believe electrical, it gives me a really low 1st, so I can put a higher gear in my rear end and still have the super pull mode that I like, and with the high 5th gear I think I can enter big block territory without effecting economy.  I know there is more work going from auto to manual.  For the engine I can't afford to start fresh so I'm going to have to take what I can find.  Bare minimum  want to find another 350 or 383 or something and clean it up.  All my engine accessories are less than a year old and all the wiring is fresh.  So If I'm lucky I will get away with maybe replacing a cam and lifters and gaskets doing a basic overhaul.  I don't drive a racecar.  I was thinking the big truck 427 would be nice for the extra durability, although they are supposedly expensive to build for performance, or whatever I find in front of the 4500.

My biggest issue is I really don;t know where to start.  I know that used engine/tranny can be had for cheap if your careful, but where would be a good source of info so I can learn what to look for and what needs done.  I enjoy doing things like this myself, I just don't have the experience to just jump in without guidance and could use a little push to source correct parts for my range.  If anyone knows of good breakdowns, exploded diagrams, important things to look for it would be very much appreciated.


Also, no I am not looking to turn a thirsty giant into a prius and I know at most I will only turn out 10-15 mpg conservatively.  Having better highway manners while remaining heavy duty will make me happy.

Thanks

[Da67goatman]

Build everything you'll be swapping then swap everything at once, you can swap entire drivetrain in a weekend for minimal downtime.  Build a solid 454 and have a 700r4 prepped for it and mileage and power will always be there.  A friend of mine has a built 454 700r4 and 44s and gets ave 18mpg with the ability to light those massive meats into 3rd.  Do it right, do it once.  I say drive it as is until the rest is built ready to drop in then mad thrash weekend.

[tsroark]

Hey, thanks for the response.  Is that tbi or can I keep my 4 barrel?  Will the 700r4 be able to handle the abuse that I put on it, would it be better than the 5 speed manual?  I had been looking into the 700r4 a little due to the overdrive but it seemed to much of a strength down grade to my 400, this also had me doubting the 4l60.  It's nothing for me to end up with a couple thousand lbs on the back and a few more on a trailer behind.  What am I looking at cost wise?  I did plan on swapping everything at once, though.  I had to drive a dodge while I swapped cabs last year, I don't think I could do that again.

Tim

[Irish_Alley]

lets start with this, if you keep the 4.10 then this kill your mpgs unless you have od a nv4500 has od. if i had the cash flow i would op for maybe a 400 at the most i would need is 400 hp nv4500 and 4.10. what i have now is a 350 sm465 and 4.10s turning 38s in the mud shes good and hauling shes good. only problem she doesnt like to go much above 70 neither do i with 38s so its all good. the nv4500 is both great for hauling due to 1st and good for the 5th gear. a 700r4 or 4l60 are good trans imo but if i was to build something up i would go with the 4500 to handle everything i could throw at it with 400 hp/tq

[Fairlane514]

Another option......keep the TH400 and put a Gearvendors overdrive behind it. They can handle 1100 hp, with only 4hp per 400 hp parasitic loss. Build a 454 for easy bottom torque, use aluminum heads and intake to keep some of the weight down.

[tsroark]

Alright, thanks for the information everyone.  I think I will go ahead and find myself a  93-95 gm 4x4 1 ton with a decent 454 and a nv4500.  I'm hoping I won't end up having to do a full rebuild and just do cleanup, maybe seals and timing chain, cap and rotor, plugs and wires, etc.  I am willing to go deeper into things but budget does unfortunately come first.  I will probably have to find an 86+ 205 as from what I understand they have the correct round bolt pattern to bolt to the tranny.  After it's all said and done I will think about changing the differentials from 4:10 to 3.73 or 3.23 or whatever the correct numbers are, if I feel I need it.

I know I will need on top of the engine/tranny:
   pedal assembly, will the assembly from the 93-95 fit in an 80 with or without modification?  I guess the cab is actually from an 86.
   clutch hydraulics, do I need to worry about my brake booster does the clutch not need outside power?  Or can this be done mechanically easily enough?
   driveshafts, will there be much length difference between the 350/400/205 and the 454/4500/205?
   tranny crossmember
   shifter linkage, I will have to rework my doghouse
   What about cooling, I currently have a cooler for my th400, can I use that setup for the 5 speed or do I not need to worry about it?
   exhaust, it will have dual exhaust, no cats and no fancy muffler.  I've actually got new straight pipes from my cab swap last year.

I think thats all, but please correct me if I'm missing something or just flat out wrong?


I guess now is a great time to learn how to drive a manual.