School Me on 4L80s

kcox506

kcox506

Well-Known Member
Joined
Oct 14, 2013
Location
Hayesville, North Carolina
I am working on my cousins YJ project. Which seems to change direction everyday. He is using a SBC 350 that will be built up a bit, and wants to run a 4L80 trans. This was originally using a built M22 and D300 combo (I don't know the specs on all that but here we are). I am looking for a 4L80 for mockup so I can drop the mockup motor and trans in place. I am not familiar with 4L80s across the years so I am here asking for guidance.

What years are the best years? My research tells me 99-03 ish?. I just need to mockup the crossmember and all that. I don't need one that even works. Are all the 4wd 4l80s the same case and mounting configuration? I read the 97 got new trans cooler line locations but can't verify if trans mount or case dimensions change. I have a line on a 95 4L80. would that work for what I am trying to do? He will be ordering a new built one or sending one off to be built. Not my problem. Just need to make mounts plus swap in axles all that fun stuff.
 
You will be left with a really short like 15” driveshaft unless you do a serious rear stretch and it will be a heavy sob. Honestly 4l60 for a jeep with low gears in the transfer add is a better option unless you’re building a rock bouncer or an ultra 4. They have a bad rap because people tow with a 6k lb suburban and wonder why their trans fails or big power drag slick cars try to launch with them. With low gearing and a few upgrades like the sunshell etc, it will last.
 
150 vs 236 lbs dry 360vs 440 lb ft capacity 23.4” vs 28.5” to transfer-case mounting. Yj already has a short driveshaft

Also the 4l60 has a lower 1st gear 2.48 vs 3.06 in a 4l60 and less parasitic losses, it will make less heat too, the yj has a tiny radiator compared to a chev truck they come stock with 2 16” electric fans in gmt800, you can fit one 18” in a yj.

You’d gain weight in a bad spot, heat soak issues, and a higher 1st gear for no benefit unless you’re doing a 4400 type build with rear mount radiator, long wheelbase etc. a small block 350 will not make the power to kill a 4l60 in stock form even with a mild cam
 
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Shreddinlettuce said:
You will be left with a really short like 15” driveshaft unless you do a serious rear stretch and it will be a heavy sob. Honestly 4l60 for a jeep with low gears in the transfer add is a better option unless you’re building a rock bouncer or an ultra 4. They have a bad rap because people tow with a 6k lb suburban and wonder why their trans fails or big power drag slick cars try to launch with them. With low gearing and a few upgrades like the sunshell etc, it will last.
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It will have trailing arms and 4 link front. D60/14B combo. The wheel base will be stretched a good bit. He will be making a good bit of power. It’s gonna be an ultra4 inspired build but wont be racing it. Just rocks/dunes. I cant recall what HP he is shooting for. I’ll clarify those details and edit the post.
 
untchabl said:
Unless he is going to street drive it alot, I'd just put a Turbo 400 behind it. Don't really need overdrive in the rocks/dunes.
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He wants to keep it street legal. So that’s how we landed on 4L80 over TH400. However I never pretend to know what I don’t know. So open minded any all suggestions. Maybe the correct solution isn’t a 4L80 at all.
 
untchabl said:
Unless he is going to street drive it alot, I'd just put a Turbo 400 behind it. Don't really need overdrive in the rocks/dunes.
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that eliminates the need for a trans controller, but still big and heavy, trucks are like 130” wheelbase, jeeps are 93.5 plus whatever stretch you do. Take a 400, d300 combo and a d60 or 14 bolt and your driveshaft is super short so the angles suck. Less than 10 degrees and there is no appreciable power loss or binding in a joint, at higher angles it can be 30-50% and the short shaft steep angle will limit suspension travel. I wouldn’t look into a 4l80 until 110” wheelbase.
 
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