Looking to up-grade my K5 trans and case

[K5dreamer]

x2 that the easiest solution will be to have the trans and tcase rebuilt and put back in truck....

that being said. now would be a wonderful time to upgrade to an overdrive trans. Id have to check lengths to see if you could keep your current driveshafts, but if it were me, and its just a mild 350, that see's mostly street/light trail use, id go to a 700r4/np208 setup. deeper first gear for better off the line acceleration and offroad crawling, and overdrive for lower highway rpms.

just my 2 cents.

according to the tech specifications here, in 1985, the t-case was a NP208 only, but both the TH350 and 700R4 were available options. so the 700r4 should be the same length as the th350, dunno how the NP208 compares to the NP203 though, but even a 700R4/NP203 would be an upgrade from your current situation, and aside from the TV cable, should be a direct bolt in. parts for this should be easy to find from any 80's blazer equipped with that transmission.

 

[sweetk30]

. so the 700r4 should be the same length as the th350,.

that is wrong. the 700r4 is longer as it has 4 gears forward . = more parts in case and longer. if i recall its 1&3/4" or 2"

 

[K5dreamer]

that is wrong. the 700r4 is longer as it has 4 gears forward . = more parts in case and longer. if i recall its 1&3/4" or 2"

i guess they have different length adaptors? cuz if they are both offered that year, with the 203 tcase, it would be silly to have four different driveshafts. so i suppose the correct thing to say would be the th350 + adaptor, and 700R4 + adaptor, are the same length.

 

[82355]

They aren't the same length. That is why when you see a TH350 swapped in place of a TH700R4 in a 80's Chevrolet, they have that spacer between the adapter and the transfer case.

Also, he has a TH350/NP203. You are talking a TH700R4/NP208.

The easiest way to do that upgrade would be to find a parts K5 with a known good TH700R4/NP208, and swap the whole thing (tranny, transfer case, shifter, cross member, etc).

Martin

 

[K5dreamer]

oh dang, my mistake, saw both trannies as an option with the same t-case, figured they worked it so they would be the same effective length. this is why yall are here to call me on my BS

 

[liljoe8865]

swaping the TH350/np203 for a 700r4/np208 sounds like a good idea?

just trying to get some answers you guys are awsome now should i just rebuild the TH350/np203 or upgrade with 700r4/np208 in a 1979 chevy k5 cheyenne? which one is better i do have 1ton axels all the way around the truck with front locking hubs with 350 engine

 

[bailey9r]

It all boils down to better 700r4 performance (acceleration and gas mileage) or th350 in good running condition and where you were before.

It will take a bit of work tracking down plentiful parts to swap it all out or for about the same cash get your stuff rebuilt.

I would go with the 700 route and end up at least 25% better mpg (over drive and part time 4*4) That is assuming you have decent ratios in the rear end. Just my 1.5 cent worth.

 

[liljoe8865]

yup thats what i wanted to know i dont want to re-build when i can do the swap for just as much but which route to go is the problem just trying to get as much info as needed to do the job.

 

[imiceman44]

My memory must be shot. I remember my best friend's 76 Blazer having a smallblock 400 CID, AND a TH400, and a 203. But, that was a lot of years ago. Might have all been swapped in???? OK memory is shot.

And no your memory is not shot.
I don't care if the experts claim they know, but I had the original order sheets for a 76 blazer and it said th400 optionnal with 400SBC.
I am sure not many opted for it but it WAS offered in 76 and 77 for sure.
I can't vouch for any other years since I never saw any litterature for that.
And in those years by the way the only option with an auto was the 203.

 

[sweetk30]

everyone is forgettin that 700r4 dont like big tires and tall highway gears.

inorder to effectivly use and gain use of overdrive on a 700r4 you need some deep gears . or the tranny will cycle 3-4 shifts hunting for the sweet spot. and most guys here find 35-38" tires = 4.88-5.13 gears for best overdrive use without the tranny hunting for the best gear.