Well I really want to do this now, now that I thought of it. Does anyone have any info on this swap? Links would be great for part sources. I am pretty positive I am going to purchase a 1991 yj next week it has a 5 speed in it. I do not know much about jeeps at all but I am fimilar with GM late model engines and I know that these 5.3 can run pretty well and better with A mild cam I'll throw in it.
I know there are both adapters out there to adapt the GM engine to the jeep transmission and also adapters to adapt gm transmissions to the jeep transfercase. I am not sure what would be the best solution. I can get a th350 trans pretty cheap that would bolt right up to the engine than I would have to get the adpater for the transfer-case.

Any input and suggestions would be greatly appreciated guys. Thanks!!

 

If you do the 5.3 swap into the YJ you are better off ditching the entire drivetrain. The Dana 35 and Dana 30 will never hold up to the 5.3. If you do decide to keep the axles I would for sure swap out the tranny and T case for GM stuff. The 5 speed tranny in the YJ's is junk. The T case is a NP231 and will probably be okay depending on how hard you drive it. GM used NP 231 t cases behind their trucks in the 80's. But the cases between the Jeeps and the GM trucks are a little different.

 

you need to get a certain flexplate and spacer to run th350 / th400/ or 700r4 behind the 5.3 or any lsx for that matter, as I understand it they are factory parts. I was looking into that conversion myself but plan on using the 700r, with a frankenstein t-case....use the gm t-case front and the jeep np back half of the case, it will bolt up to the 700r without the use of an adapter. the jeep and gm np231's are almost identical except for the way they clock on the trans.

 

What would have to be done in order to use a GM tcase? Would you need different drive shafts?

 

What output shafts do the GM 231 case use? I'm assuming the rear is still a slip yoke style?

 

This is a TJ but start with it. https://ls1tech.com/forums/showthrea...highlight=jeep

You you'll need a driver side drop transfer case Like a Gm NP241 with a VSS and a 4l60e. Then you have the option of a slip yoke eliminator to help with the rear drive shaft length. Plus it will have a decent low range and little more strength than a NP231 but you can get adapters to use the Jeep NP231 just add a VSS.

The axles aren't just going to blow up, but will break. **** I would run them till they break then swap in some dana 44's later to save money up front.

 

What are you planning on doing with this Jeep? Are you going to use it as a trail rig or just something to rip around in? Either way you will want to look at axle upgrades. Like Bo185 said, you could run the stock D35 and D30 until they give up and then swap in some D44's or if you really want some grunt axles go with some D60's. But the D60's may be way overkill depending on what you plan on doing with this Jeep.

I'm working on a similar project. I'm putting a 5.3/4l60e into a 1985 Toyota truck that is being built as a dedicated trail rig. V8 power, 1 ton axles, and 40 plus inch tires.

 

Im just looking at trying to make a decent on and off-road jeep with some decent power, not like hardcore wheeling or anything crazy, but something that will get me through some deep mud sometimes and maybe some decent hills.

 

In that case you will probably be okay for a while with the stock axles, depending on how much skinny pedal you use and what size tires you run. If you already have the turbo 350 then it might be easier to ge the needed parts to bolt it up to the 5.3. If you don't already have a trans I would for sure go with the 4l60e or the 4l80e. I think you will really like having that 4th gear. Plus they have a lower first gear than the turbo 350. There is tons of info on the web for V8 swaps into Jeeps, This swap has been done countless times. You should be able to find all the answers you need.

 

I'm still running on my stock axles in my '01 Jeep TJ (d30/d44) with a head/cammed '05 5.3L transplant powering them. I wheel on a variety of different types of terain about once a month or so. I'm hardly easy on the drivetrain. Anyhow, just saying that the axles aren't exactly as brittle as people tend to make them out to be. Now I have heard that the 35 is much more prone to breakage, but I've never had one so can't say..

That said, I don't expect these axles to live forever either. Planning on a D60 swap eventually.

 

Here's a few picks of my swap into 99 Wrangler.

Runs great. Great power.

 

Dana 35s have been known to break on the street with 33s and a 6 banger, they won't hold up to anything fun behind a 5.3. Swap in an 8.8 out of an explorer for a couple hundred bucks and call it good. Swap some newer XJ or TJ non-disconnect 297 shafts into the D30 and it'll be fine up to 35" tires if you're smart about it. Don't bother "upgrading" to D44s. The 8.8 is stronger and cheaper, and the D30 is too believe it or not. D44s have better balljoints, rebuildable wheel bearing assemblies, more aftermarket, etc, but they use the same u-joints as the newer D30s, which is what breaks first 75% of the time. Plus on top of that every stock D44 shaft I've seen necks down to a smaller minimum diameter than the D30 shafts. So if the joints hold up the D44 shaft will actually break first, and it's happened to my buddy several times.

The stock AX-15 trans is definitely on the weak side, I'd upgrade if I were you. NV3550 or 3500 or whatever it is the 1/2 tons used might be a good choice, NV4500s are damn good but probably overkill for a mild rig.

If you use a 700R4 the t-case swap is easy. Pick up an S-10 NP231, pull the input shaft and planetary assembly out, and throw it in place of the ones in the Jeep case. If you're lucky the S-10 setup will even be a 6-planetary instead of the 3 that Jeep used. At most you might need to buy a clocking ring for $75 if the hole spacing is different. My case is flipped so I'm not sure how it normally lines up with the holes on the stock adapter. Now that I think about it, just use the S-10 case. Bolt the YJ front output yoke on it and you've got the same case, drivers drop, wider/stronger chain, and 27 spline input. Some S-10 NP231s use 5 bolt mounting, some use 6 so make sure you get the right one. Don't bother with the trans out of the S-10 though, it won't bolt up to the V8.

I'm in the middle of a 6.0 swap into my Scrambler but little I've done is gonna be much help on a mild YJ build. Shoot me a PM if you have any specific questions. I'm running a 2003 LQ4, built 700R4, NP231 crawlbox with241 internals, and Dana300 backing that up. 120:1 lowrange and ~450 lb-ft should be fun.

 

lsxyj on here did a killer job on his yj. 5.3/4L60E/Stak Dana 300/D30F/F8.8R. Check his thread