Topic: four angry squirrels swap to a 4.0L in a 91 YJ

[swatsniper1s1k]

i've done the pricing, and considered just about every option, but this is a tentative final set up after talking to a number of 4wd shops and some guys from the local jeep club.

Chevy 5.7L fuel injected
Jeep NV3550 Trans
I'll swap the input shaft and do a rebuild kit on my NP231
a Bellhousing adapter from Advance Adapters for the Chevy V8.
and a heavy duty radiator to keep it cool.

if i can get a complete 5.7L with half decent mileage from the junk yard along with the transmission and maybe the attached np231, i'll do a rebuild kit on the trans and t-case myself. should take about a week or so to rebuild. get the 5.7L tuned, and drop it all in. the rear axle is probably the only one i would swap initially, because it's the only axle i use in daily driving. i only break out the front in snow or off roading, so no need for a little while, plus it would start to get too expensive. any specific recommendations on rear axle that can handle the 5.7? and i'm not gonna drop a dana 60 on it...yet as for getting it emissions compliant, according to the 4wd shop that has done a swap like this recently, they just dropped on a catalytic converter from a '99 Tahoe and it passed flying colors.

[Bounty Hunter]

Run a Ford 8.8 rear axle, it can handle the 5.7L engine.

Why bother with a jeep transmission and bellhousing adapter when you can get a GM transmission that will bolt right up?  Didn't GM use the NV4500?  Or other manual options?  GM also used the 231C and 241C that will bolt up behind the GM manual transmission.  The 231C will use the same SYE's and other mods as the 231J, but the 231C can often be found with a stronger planetary gearset and wider chain set to handle the v8 torque.

[chardrc]

Run a Ford 8.8 rear axle, it can handle the 5.7L engine.

Why bother with a jeep transmission and bellhousing adapter when you can get a GM transmission that will bolt right up?  Didn't GM use the NV4500?  Or other manual options?  GM also used the 231C and 241C that will bolt up behind the GM manual transmission.  The 231C will use the same SYE's and other mods as the 231J, but the 231C can often be found with a stronger planetary gearset and wider chain set to handle the v8 torque.

i thought the 231c didn't accept the SYE for the 231j which is why people usually use the front half of the 231c and the back half from the 231j

[Bounty Hunter]

i thought the 231c didn't accept the SYE for the 231j which is why people usually use the front half of the 231c and the back half from the 231j

The back halves are pretty much the same, the rear case halves are identical.  A 231 SYE will work in a 231C and 233C.

[Jeffy]

i thought the 231c didn't accept the SYE for the 231j which is why people usually use the front half of the 231c and the back half from the 231j

The main difference between the 231C and the 231J is that the C has a 5 bolt pattern on the input while Jeeps and Dodges use a 6 bolt pattern.  Chevy's also use a 27 spline shaft so, which is stronger then the 23 and 21 the Jeep and Dodge use.  Chevy's are usually a HD version so it should have the 6 gear planetary and the 1.25" chain and sprocket set as well.

As for transmissions, I would recommend getting a complete engine and transmission at the least.  Although you'll find that 90% of the late models are automatics.  The other thing to noise is what 5.7L are you going to use.  5.7L = 350 cid.  So it could be carbureted or EFI depending on the year.

If you go with an EFI I highly recommend looking for a early to mid 90's 5.7L which is a 'Vortec' BUT pre-OBDII.  Actually IIRC, they aren't truly Vortec's.  The engine can be found in C/K50's and C/K100's  Actually, I think they had changed to the C/K1000 and the C/K1500.  These are the Full-size Blazers and the 1/2 Ton Pick-ups.  The manual in them, I think is still a NV3500 if you can find one.  The Auto should be a 700R4 which is an excellent transmission.

Also, I think you'll find most of these trucks are 2wd which means you'll have to take the tail cone off the transmission and get a adapter.  Adapters are $$$ especially if you don't have to use one.  You'll have $$$$ if you can stay away from using adapters.  Then use that money to buy a Painless wiring harness that's plug-in.

On and you'll need to get a conversion radiator and not a Jeep one as the inputs and outputs are on the opposite sides as the Jeeps.  The 5.7L will want to be routed to the drivers side.  Places like Radiatorbarn.com or Jeepradiator.com have them.  Otherwise get a universal and jsut drill your own mount.

[st.chevrolet]

JB Conversions  makes a 231C HD Super Short SYE, 3.125" shorter than other HD SYE's.

[Bounty Hunter]

It will be the same as any other 231 super short sye.  It's what I run in my 231j, with a Chevy 6-gear planetary, wide chain setup, and 2lo.

You can have a radiator shop move the lower neck of a jeep radiator to the opposite side for use with the GM engine, and use a straight thermostat housing to reach the upper neck.  Or a conversion radiator, whichever is cheapest and easiest.

[swatsniper1s1k]

i'll check the local yards to see if i can find the GM NV4500, but the nv4500 will run me almost double the $ of the nv3550, and the rebuild kits are much more expensive too. the bellhousing adapter would be cheaper than the ready to bolt up 4500 with a rebuild kit. the 4500 is what i was originally thinking of, but after talking to the guys, it's sometimes problematic on fitting it into a jeep. the 4500 is indestructable, but the 3550 will handle just fine behind the v8 power plant. i personally distinguish 5.7L as fuel injected and 350's as carbed. i'm looking for an EFI 5.7L. the 3550 also bolts right up to my np231, once i replace the input to 23 spline.

btw i just pulled a passenger side mirror that the jeep was lacking. it just didn't come with one, so i pulled one off of a 97. $15 for it and 2 minutes to pull. not bad...

[swatsniper1s1k]

and call me ignorant, but what does SYE, SOA and SUA stand for?

[Jeffy]

i'll check the local yards to see if i can find the GM NV4500, but the nv4500 will run me almost double the $ of the nv3550, and the rebuild kits are much more expensive too. the bellhousing adapter would be cheaper than the ready to bolt up 4500 with a rebuild kit. the 4500 is what i was originally thinking of, but after talking to the guys, it's sometimes problematic on fitting it into a jeep. the 4500 is indestructable, but the 3550 will handle just fine behind the v8 power plant. i personally distinguish 5.7L as fuel injected and 350's as carbed. i'm looking for an EFI 5.7L. the 3550 also bolts right up to my np231, once i replace the input to 23 spline.

btw i just pulled a passenger side mirror that the jeep was lacking. it just didn't come with one, so i pulled one off of a 97. $15 for it and 2 minutes to pull. not bad...

NV3550 is a Jeep transmission.  It is an offshoot from the NV3500 which is used in GM's as well as Dodges.  You won't find a NV4500 with a 5.7L OE.  NV4500's are found in 3/4 Ton and 1 Ton Trucks while the NV3500 is found in 1/2 Ton trucks, OE.  Personally, I would find a C/K1500 or a C/K2500 and get the whole truck.  Preferably a side or rear accident.  Then pull everything out of it at once.  Forget about grabbing a part from here and there as that's going to just complicate the whole thing.  Unless you really want to mix-and-match.  Like I said earlier though, adapters are expensive.  You'll be looking at probably $1000-1500 in adapters.

The engine you want is called a LO5.  It was used from 1987-1996 and is TBI and OBD-I.

[FourbangerYJ]

and call me ignorant, but what does SYE, SOA and SUA stand for?

SYE= Slip Yoke Eliminator
SOA= spring over axle
SUA= spring under axle

[swatsniper1s1k]

ok, so if i won't find an NV4500 mated to a 5.7L oe, then how do i get that out of C/K1500/2500 along with the engine and all? just trying to figure this out and how likely i'll be to find the C/K1500/2500 with the engine and trans intact...i haven't seen many of the gm made trucks/suv's with both engine and trans... i feel like such an  for asking so many questions. but how else do you learn right?

[st.chevrolet]

It will be the same as any other 231 super short sye.  It's what I run in my 231j, with a Chevy 6-gear planetary, wide chain setup, and 2lo.

You can have a radiator shop move the lower neck of a jeep radiator to the opposite side for use with the GM engine, and use a straight thermostat housing to reach the upper neck.  Or a conversion radiator, whichever is cheapest and easiest.

There  are a lot of differences between other super short SYE's (such as the Extreme Short SYE or Mega Short SYE) when compared to a JB Conversions Super Short SYE.

[Jeffy]

ok, so if i won't find an NV4500 mated to a 5.7L oe, then how do i get that out of C/K1500/2500 along with the engine and all? just trying to figure this out and how likely i'll be to find the C/K1500/2500 with the engine and trans intact...i haven't seen many of the gm made trucks/suv's with both engine and trans... i feel like such an  for asking so many questions. but how else do you learn right?

Buy the whole truck would be the best option.  Then you can sell off what's left.  You might even be able to make money on it.  The downside is that you need the space for the truck but you're assured all of the OE pieces you might need then some.  You'll have to figure out the exhaust.  IF you're in an emission state then you'll have to check your local laws.  Going with a OBD-I means there will be less computer controlled stuff and a lot less emission stuff.  It will probably have a single car instead of a bunch of pre-cats and a cat.  Worst case is getting one with dual exhaust with two of everything.

[swatsniper1s1k]

Buy the whole truck would be the best option.  Then you can sell off what's left.  You might even be able to make money on it.  The downside is that you need the space for the truck but you're assured all of the OE pieces you might need then some.  You'll have to figure out the exhaust.  IF you're in an emission state then you'll have to check your local laws.  Going with a OBD-I means there will be less computer controlled stuff and a lot less emission stuff.  It will probably have a single car instead of a bunch of pre-cats and a cat.  Worst case is getting one with dual exhaust with two of everything.

thanks jeffy, that actually made a lot of sense...i don't know if it's cuz i'm wasted out of my mind right now, or cuz it is logical, but as for the emissions state, the car is registered in PA,