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95 K1500 4l60e to 4l80e swap
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Post 95 K1500 4l60e to 4l80e swap 
Hey guys just have a quick question. I am considering swapping my 4l60e to 4l80e in my 95 heavy half for towing purposes, but I have been finding some conflicting information. I have always been under the assumption that all transmissions offered in 88-98 trucks bolt up exactly the same with the trans crossmember in the same place. Am I wrong on this one? I know an NV4500 will bolt into the place of a 4L60 as I have done it in my 92, but I am seeing people say that the 4L80E is longer, forcing me to move back my crossmember and change driveline lengths as well as cooler lines. I am just curious if anyone can give me a definite yes or no on this one. Your help would be greatly appreciated.

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Post Re: 95 K1500 4l60e to 4l80e swap 
thegmguy wrote:
Hey guys just have a quick question. I am considering swapping my 4l60e to 4l80e in my 95 heavy half for towing purposes, but I have been finding some conflicting information. I have always been under the assumption that all transmissions offered in 88-98 trucks bolt up exactly the same with the trans crossmember in the same place. Am I wrong on this one? I know an NV4500 will bolt into the place of a 4L60 as I have done it in my 92, but I am seeing people say that the 4L80E is longer, forcing me to move back my crossmember and change driveline lengths as well as cooler lines. I am just curious if anyone can give me a definite yes or no on this one. Your help would be greatly appreciated.


in a nutshell - yes.

the ports for the lines are in different locations, as is the mount - the trans is longer and would need a shorter shaft as well as i different yoke.......think i got em all, if not someone will chime in.

should be able to use the factory crossmember and either slide it back or slide and drill....

its about the same difference between a T350 and a T400 (60E to 80E)

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ok that is good to know...i guess i better make up my mind now haha

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wait - i just saw K in the K1500 - im not up on the 4x4, but the trans is bigger, and the lines and mount will be different.......

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So will the crossmember still need to move back? Drivelines still need changing? I don't have one to measure.

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thegmguy wrote:
So will the crossmember still need to move back? Drivelines still need changing? I don't have one to measure.


im pretty sure from what i remember the 4x4 guys that have done it, yes...

the trans being larger/longer will move the transfer case to the rear a bit. if i recall, you will have to change the input on the transfer case as well....

would need one of them to chime in here - my element is not in the 4x4 field....

just shooting from the hip, you need to get new lines or modify yours, figure out the cross member, input shaft on the transfer case, and i think shorten the rear shaft, but the front can still work....

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Yes, the mount will need to be moved back, the cooling lines will need to be extended, the front driveshaft will need to be lengthened and the rear driveshaft will need to be shortened. I just made this swap on my 2000 Silverado, and the transmission I used would be the exact same one used on your 95. You will also need to get the computer programmed to control the 4L80E, and there are a couple of wires to be moved around. Since your 95 is an OBD1 truck, I don't know what will be required on the computer side, or exactly how the rewiring will need to be done as it's different for an OBD2 truck and different for a GMT800 vs GMT400.

You can check with the salvage yards for the driveshaft from a 4L80E-equipped truck, configuration doesn't matter because they will all be the same for the front driveshaft. Or, just take your old one down and have it lengthened. I had my front shaft lengthened and my rear shaft shortened for like 150-200 bucks, don't remember exactly what it was. This was also with new U-joints installed all the way across although I had to supply the U-joints because the shop I used didn't carry the ones I wanted.

You're going to have another small problem, the output shaft on the 4L80E isn't going to work on your transfer case. You can either have the 4L80E built with a 4L60E output shaft, get your existing transfer case rebuilt to accept a 4L80E output shaft (the way I went) or pick up a transfer case that will both work in your truck and accept a 4L80E output shaft.

On the cooling lines, I screwed mine up by cutting them too close to the engine which would have put the rubber needed to extend them right next to the exhaust. I was forced to buy new lines as a result. The good news, I was able to get the new lines for like 10-20 bucks each new from the dealer and they were pretty easy to install. It took about 1 hour to run the new lines and the engine didn't have to be jacked up. This may or may not be the case on a GMT400 truck. I would suggest, that if you go this way, that you install the new lines while the trans is out of the truck. It would have been even easier had I been able to do this. And on the cooling lines, make sure to flush the coolers out before connecting them to the new trans, and flush the lines if you reuse the old ones.

On moving the trans mount, your truck has a different style crossmember than mine does. You should be able to just slide the crossmember back to the correct spot, and the holes might even already be drilled if your specific configuration was also offered with a 4L80E. If it wasn't and the holes aren't there, you'd just have to drill holes in the frame in the correct spot. I had to have a whole new crossmember made up that moved the mount back to the correct location as my frame has a welded in mounting point instead of holes to bolt to. Mine is probably stronger than yours, but was a huge pain for putting in something that doesn't belong.

One other thing on the transmissions. The 4L60E comes with a 3.06 first gear and the 4L80E comes with a 2.48 first gear. This will mean that the new trans will feel slower on takeoff. I compensated for this with the TCI low gear gearset that changes the 4L80E to a 2.75 first gear. 2nd gear is also different between them, but the difference is not so great and the TCI gearset also compensates. The 4L60E also has a .69 or .70 overdrive where the 4L80E has a .75 overdrive, which means higher RPMs on the highway. I swapped from 3.73s to 3.42s and put oversize tires on to compensate for this.

Now for the big question. After having gone through all this trouble, would I do it again? Absolutely. I'd rather go through all the hassle to make the swap for a trans that will likely outlast the truck than go through 4L60E after 4L60E.

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Shorten the rear drive shaft 42mm. Move the cross member back (42mm) and re-drill the 4 holes. Change the transfer case input shaft to the larger 32 spline unit.
make your wiring changes as per Jeff/Lextech's spreadsheet. Flash the new tune into the PCM. Speak to Noel (NU72) about the cooling lines....he found some from a different model that are a direct swap/fit. I didn't adjust the length of the front drive shaft....it's telescopic and has quite alot of travel.

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Thanks for the great info. I also have a 95 K1500 and comtemplating the swap to make it bulletproof. Also have a 9.5 inch 14 bolt laying here thats going in first.

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