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Alexjk 03-29-2012 06:42 PM

k20 drivetrain swap what to look for
Found a YJ that had a drive train swap from an 88 k20. includling axles. The price is right for what I want to do with it but I am totally unfamilar with this engine/tranny. Its a 350 with a 465 tranny 4 speed and 3/4 ton axles. Has a granny gear (real low first gear right?) It needs the front driveshaft and 4x4 shifter hooked up and the speed/tach hooked up as well. Says he has all the parts for everything but just hasnt finished it up. Im assuming a driveshaft will have to be made which is no big deal. What should i look for specfically when i look at it? Is the k20 a good drivetrain? pros? cons? Is it a full time 4wd set up or does it have manual hubs?

busemans 03-29-2012 08:47 PM

thats a blazer, right? the 350 is the normal chevy small block, the trans, i am unfamiliar with. it will have a shiftable t-case, like our jeeps do. 2 and 4 wheel settings.

Laguna S-3 03-29-2012 08:47 PM

The front is probably a 8.5" 10 bolt, strong, but, breakable. The rear could be a 9.5 or a 10.5, 9.5 tough but weak under stress, 10.5 is full floating, heavy but, very tough. the 4 speed is d..m near industructable as is the 205. depending on your purpose of the rig, could be a good deal. Manual hubs, the front drive shaft is the same as 1/2 thru 1 ton. Good luck, Ron

DirtRider1357 03-29-2012 10:30 PM

thats a very good drivetrain. 10 bolt is your basic rear for the front. my 86 k10 had a 10 both in the from and a 12 bolt in the rear. both are good, 12 both being stronger. and then there are the full float and semi float 14 bolt rears. i know laguna already said that im just using bolt numbers instead. to find out what rears are in the jeep, just count the number of bolts on the diff cover.

4Jeepn 03-29-2012 10:32 PM

the 10 bolt is the dana 35 of the chevy world...

DirtRider1357 03-29-2012 10:56 PM

but its still a lot stronger than the d35. my old k10 ran 38.5x16 r15 super swamper tsl's with a 10 bolt front and 12 bolt rear. the 10 bolt did have chromoly axles tho

Alexjk 03-30-2012 05:58 PM

cool thanks for the info guys. Im still on the fence about it. Its not entirely put together just yet. The owner said he still has to have the driveshaft lengthened and mod the 4x4 shifter still, and im sure theres a few other odds and ends. I could go either way on it, im uneasy about it not being 100% done even tho it runs and drives and for the money im sure I could find a drivetrain im more familar with for the YJ i have. Its a tough call.

Norcal_Chris 03-30-2012 09:13 PM


Originally Posted by DirtRider1357 (Post 2198568)
but its still a lot stronger than the d35. my old k10 ran 38.5x16 r15 super swamper tsl's with a 10 bolt front and 12 bolt rear. the 10 bolt did have chromoly axles tho

Musta only ran mud with it.

I had a blazer before my yj. started with d44/12b and 33s Broke the 12b on some pretty mild rocks.

Then went to a d44 3/4 ton with a 14b rear and 36s. That lasted fine with no breakage

Then went to d60/same 14b rear and 42s. No breakage except driveshafts.

That drivetrain is a nice setup for a light jeep. the 10b front should work just fine if your gonna run 35s. My buddy runs 37s on a 10b front and has only popped a u joint once but it was at full lock.

The sm465 is an awesome trans but SUCKS on the road. Its literally like driving an old dump truck. 20ft space between shifts and it likes to make noise and grind and whine and you cannot shift fast. The low is nice and you will enjoy it.

The 205 is one of the strongest transfer cases around. Can be twin sticked with ease by doing some mild grinding on the detent rod for the shifters. It will however most likely have the 10spline 205 wich is less ideal, but agian, with a jeep it isnt as bad.

Hopefully he kept the TBI setup on the motor. If so it will work great offroad and take angles very well. It is basically a carb with 2 fat injectors in it.

I have been a chevy guy for a while, and sounds like a few others are pretty familiar. so if you have any other questions im sure we can help you out.

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