Lots of Questions about 4L80E Swaps

hummer4x4guy

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One note i'd like to add is the 4l80 internal wiring harness issue that they can leak. I had to replace the harness inside my transmission because it was damaged. The one I replaced it with was not of the best quality and the trans fluid would leak through the bulkhead plug and seep through the holes in which the wires passed through. I have since bought an AC Delco made wiring harness and its build so as not to leak fluid part # is 24241218 and bout $50. Id also suggest replacing the internal solenoid valves while you are in there and if you're unsure of the condition of the solenoids. Cost about $100 for a 7 piece kit.
 

richingalveston

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I second the leak on cheap internal wiring harness.
my first build before the TCI POS computer blew it up, the harness leaked, first rebuild guy used cheap harness.
second rebuild got the better harness, no leaks.

so when you have the tranny rebuilt, ask about the wiring harness and which one they are going to use.
I have 1009, not HMMWV but have 4l80e
Rich
 

rebelmfg

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Its crazy to see so many older HMMWV's driving around with only 3 speeds, seems so impractical for road use.
 

TOBASH

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Its crazy to see so many older HMMWV's driving around with only 3 speeds, seems so impractical for road use.
I agree that a 4 speed is better BUT, the TH400 is bulletproof, there is a guy in NC who will be making a special transfer case that will add a forth gear, and farmers and such who use these rigs for offroad are fine with 3 speeds.

JuanPrado states he has a TH400 that does 70. Not sure how but that is amazing. Big tires like 40's will allow 60MPH with a 3 speed. Others just drive city at 30MPH.

I went with a 765R4. I am happy without electrics. I can drive at 65 MPH with stock 37" 24 bolt tires.

Others prefer the 4 speeds with the separate electrical boxes.

Bottom line is how do you use your rig, and what do you need?
 

MattNC

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I agree that a 4 speed is better BUT, the TH400 is bulletproof, there is a guy in NC who will be making a special transfer case that will add a forth gear, and farmers and such who use these rigs for offroad are fine with 3 speeds.

JuanPrado states he has a TH400 that does 70. Not sure how but that is amazing. Big tires like 40's will allow 60MPH with a 3 speed. Others just drive city at 30MPH.

I went with a 765R4. I am happy without electrics. I can drive at 65 MPH with stock 37" 24 bolt tires.

Others prefer the 4 speeds with the separate electrical boxes.

Bottom line is how do you use your rig, and what do you need?

TOBASH will you be able to give a little review of your 765 at some point? Maybe what work they needed to do to get it in, maybe some pics or a video? I keep playing in my head between it and the positives of mechanical and easier bolt up vs the 4L80 and the required modifications and electrical needs.

I’m also interested about special transfer case in N.C. any more details? That’s where I’m at. There are some guys here also launching a turbo kit soon. A friend is a master Detroit diesel mechanic and I’m going to get his opinions on that.
 

TOBASH

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TOBASH will you be able to give a little review of your 765 at some point? Maybe what work they needed to do to get it in, maybe some pics or a video? I keep playing in my head between it and the positives of mechanical and easier bolt up vs the 4L80 and the required modifications and electrical needs.

I’m also interested about special transfer case in N.C. any more details? That’s where I’m at. There are some guys here also launching a turbo kit soon. A friend is a master Detroit diesel mechanic and I’m going to get his opinions on that.
Sure, but I’d like to run a few thousand miles on it.

I will tell you that if you get an inexperienced mechanic who does not know 700R4, and he hooks up the TV cable wrong, you will blow the tranny in a mile.

RWH swears by 4L80E. You should talk to him as he seems to have it down to a science. You will need a new crossmember and new drive shafts IIRC.

I really like the 765R4. I designed it with Bowtie Overdrives with comfortable shift points and it feels appropriate and not like a 1/4 mile dragster. No electrics and no computers. Driveshafts unchanged and some adaptation to the crossmember. I will inspect fluid next week during repairs to the stack in order to ensure no metal particles and crud in the fluid.

I will never crawl a serious area With this HMMWV, but I will drive sand and off-road. If I crawl I will use my new to me Hummer H1 with 4L80E that arrives in April 2021.

That being said, my 765R4 Diesel Truck tranny was over designed to accept 800 HP. It should be solid.
 

tobyS

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Thinking of the 4x2 HMMWV rod project concept and working back from a 41 inch rear tires, with 410 gear, at 70 mph I would need 2350 rpm. Allison 545 does not have an overdrive, but does have 4 gears.

A gas 350 chevy seems a better fit than diesel at cross country cruise speed 2350 tranny output.

I thought I'd throw the most basic of all Allisons out for consideration. The 545 is the parent to the 1545 used in A3 deuce that added the locking torque converter.....which made the 4th gear clutch the weak point.

But the 545 does not have the issues that mechanically locking the torque converter brings to the design. The 545 does not tear out 4th like the 1545 does, but there is tradeoff, mainly at max speed.

The 545 is 1-1 and TC losses may be 10%, so without overdrive, the 545 may not work at all.

Oh yea, the through clutch of the 4L80 is the same as the 545 fourth and the racing high performance clutches and steels and vulcanized piston can replace the 545 fourth and make it much stronger....and Daco can build the TC for a quality mechanical setup that is 1-1
 
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