Will a 1996 k2500 4l80 fit in my 1998 k1500 with a 4l60 both trucks have the light duty rear end one is a 6 lug the 96 is a 8 lug parts truck with a rebuilt 4l80. I have 2 14 bolt heavy duty full flouters rear ends out of a 1996 hd parts truck I bought to make a k2500hd out of the k1500 but I would like a 4l80 in it. I buy wrecks from Copart for parts.
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4l60 swap to a 4l80?
- Thread starter Mike's 52
- Start date
Will L.
Well-Known Member
Yes but it will require more modifications than just swapping them.
The transmission mount will be relocated as will the transfer case swapped or modified by changing the input shaft from 27 to a 32 tooth. This also leads to drive shaft modifications. I remember you shorten the rear shaft 1.5-2” but can’t remember how the front shaft gets altered but it does.
You need the entire shifting linkage assemblies for both trans and transfer case.
The neutral safety switch grouping and the transmission lines also but best is go to aftermarket tranny cooler. The line & cooler size is different in many trucks between them and gm later figured out the factory was undersized in the older ones.
For the controller- people used to go through a bunch of chaos modifying the ecm. Don’t, it still ends up with headaches on the 4wd. Just buy an aftermarket controller. Leroydiesel.com has a good one.
Know that the engine rpm will be a little higher on the freeway in overdrive by 5% iirc.
A couple while you are at it things- drain plug in the new trans pan for service ease and the reuseable gasket & new filter.
Put a new chain & shifting fork pads in the transfer case while it’s out of the truck, unless you can do the dream of all transfer case dreams and get an Atlas in there.
Out of interest-What engine? We all enjoy truck pics…
The transmission mount will be relocated as will the transfer case swapped or modified by changing the input shaft from 27 to a 32 tooth. This also leads to drive shaft modifications. I remember you shorten the rear shaft 1.5-2” but can’t remember how the front shaft gets altered but it does.
You need the entire shifting linkage assemblies for both trans and transfer case.
The neutral safety switch grouping and the transmission lines also but best is go to aftermarket tranny cooler. The line & cooler size is different in many trucks between them and gm later figured out the factory was undersized in the older ones.
For the controller- people used to go through a bunch of chaos modifying the ecm. Don’t, it still ends up with headaches on the 4wd. Just buy an aftermarket controller. Leroydiesel.com has a good one.
Know that the engine rpm will be a little higher on the freeway in overdrive by 5% iirc.
A couple while you are at it things- drain plug in the new trans pan for service ease and the reuseable gasket & new filter.
Put a new chain & shifting fork pads in the transfer case while it’s out of the truck, unless you can do the dream of all transfer case dreams and get an Atlas in there.
Out of interest-What engine? We all enjoy truck pics…
dbrannon79
I'm getting there!
is there a reason your wanting to go from a 4l60 to a 4l80? if the trans is slipping, your best bet is to have it rebuilt and while your at it have it "Built" for torque and HP's the cost of doing the swap, controller or modding the ECM, modding the drive shaft and transfer case is about the same if not more than having your 4l60 re-done. Not to mention all the added labor of modifying everything.
gear ratios on the OD is also different like Will mentioned you will loose some top end and have slightly higher RPM to keep the same highway speed with the swap too!
gear ratios on the OD is also different like Will mentioned you will loose some top end and have slightly higher RPM to keep the same highway speed with the swap too!
I was hoping It would fit without too much trouble. The half ton is an extra cab long bed with 145,000 miles with a 5.7 vortec 4x4. I have it listed now on craigslist in Spokane, WA. for $3,000 I'll have to try and find a k2500 pre airbag. I drive a 1979 K20 it gets 9mpg empty it's an old 350 4x4 with a trubo 400 and the cast-iron transfer case. It sucks the gas pulling my trailer with a truck on it.
MrMarty51
Well-Known Member
Welcome to the forum Mike.
Will L.
Well-Known Member
Wait… so this isn’t some kind of torque monster build thats gonna happen? I thought with the heavier duty axles going in that the trans was getting the big upgrade for power that is next or already on an engine stand like an 8.1
Please explain your plans for the finished truck, and how you are going to use it most the time. Also how hard is it going to be worked/abused and how often is that?
If this is simple transportation and not getting beat on some-
You will be light years ahead money wise to have your 4l60 rebuilt. Outside of really high torque numbers for abusive type offroading or frequent heavy towing- the 60 bests the 80.
About every 7 years is another new comer trying to make the 60 fit into Hummers because of the way better gearing. Last one was an outfit in Phoenix. The high torque of the turbo diesels and the aerodynamic brick wall on the freeway beats them up and the company gives up and usually goes out of business in the pursuit.
Hummers, 3/4 & 1 ton diesels are destined to use the 4l80 because it is like a 6’6” 375 pound lineman in the nfl that has to take constant abuse. But efficiency is not gonna happen. Lineman don’t like to run all the way down the field. The 4l60 is like a running back. Still strong & muscular, and can take a serious hit. But being built smaller it handles that 100 yard run much better.
Please explain your plans for the finished truck, and how you are going to use it most the time. Also how hard is it going to be worked/abused and how often is that?
If this is simple transportation and not getting beat on some-
You will be light years ahead money wise to have your 4l60 rebuilt. Outside of really high torque numbers for abusive type offroading or frequent heavy towing- the 60 bests the 80.
About every 7 years is another new comer trying to make the 60 fit into Hummers because of the way better gearing. Last one was an outfit in Phoenix. The high torque of the turbo diesels and the aerodynamic brick wall on the freeway beats them up and the company gives up and usually goes out of business in the pursuit.
Hummers, 3/4 & 1 ton diesels are destined to use the 4l80 because it is like a 6’6” 375 pound lineman in the nfl that has to take constant abuse. But efficiency is not gonna happen. Lineman don’t like to run all the way down the field. The 4l60 is like a running back. Still strong & muscular, and can take a serious hit. But being built smaller it handles that 100 yard run much better.
dbrannon79
I'm getting there!
Ok this is starting to make sens now, I was thinking the truck was going to be a daily driver with "occasional" HD hauling. don't quote me on this, but iirc the 4l80 and 4l60's are electrically the same for the most part, but parts are not interchangeable between the two. connecting the 4l80 to the existing ECM so long as the trans connector is pinned correctly (can't remember if the internal harness is pinned differently) it should shift. it's not gonna shift at the right times due to the gear ratios and whatnot, but I think it should at least function.
Now the torque converter, depending on what was driving the 4l80 before it was pulled from it's donor you might need to get a replacement designed for your engine. afaik the 454 gassers and the 6.5 diesels used the same torque converter, others used a different one. this is due to the low RPM stall.
On to the driveshaft and 4x4 if equipped. if you have 4x4, this is where things will be different. if the 4l80 you have already had it's transfer case, good. but if you are going to be re-using your existing one, things will need to be modified for it to mount. and for the floor shifter linkage unless it's cable operated. the trans shifter is cable operated to change gears from the column so no mods needed there. electrically IDk if they are the same or not.
Drive shaft will need to be shortened and depending on if you have a two piece shaft, you will need to be careful about the pinion angle as well. shortening it at the front shaft section between the transfer case and the slip yolk is you best bet so not to change the pinion angle. if you have a local driveline shop nearby they can fix you up. Once the trans and everything is installed, just have the truck towed to them and they'll get the driveline installed for you.
Now on to what can be the hair pulling part. if the existing ECM doesn't like the trans or transfer case, you have two options.... find a junkyard ECM that used your same engine/trans combo (giving the fact your local state will allow this, some states won't pass the inspections) or have your ECM flashed for that trans and t-case combo. If you can find someone with a real GM tech 2 and has a paid subscription to GM's tuning options they should be able to flash it, or others that do aftermarket tuning can do it also. other than this, you will need to replace your factory ECM with something like a Holley Terminator X which is fully customizable, again that also falls on how your local state is with vehicle inspections.
all in all is it worth the hassle? compare it to buying a new truck that will do everything you want... when you return home after getting sticker shocked from the price tags of a new truck on top of going into debt for as much as a house, then you can decide if it's worth the hassle of upgrading your "Now paid off truck that YOU hold the title on"
it's all do-able, it's just how much your budget is and what you want to accomplish, how it will help you, and what type of return you will get from it.
Now the torque converter, depending on what was driving the 4l80 before it was pulled from it's donor you might need to get a replacement designed for your engine. afaik the 454 gassers and the 6.5 diesels used the same torque converter, others used a different one. this is due to the low RPM stall.
On to the driveshaft and 4x4 if equipped. if you have 4x4, this is where things will be different. if the 4l80 you have already had it's transfer case, good. but if you are going to be re-using your existing one, things will need to be modified for it to mount. and for the floor shifter linkage unless it's cable operated. the trans shifter is cable operated to change gears from the column so no mods needed there. electrically IDk if they are the same or not.
Drive shaft will need to be shortened and depending on if you have a two piece shaft, you will need to be careful about the pinion angle as well. shortening it at the front shaft section between the transfer case and the slip yolk is you best bet so not to change the pinion angle. if you have a local driveline shop nearby they can fix you up. Once the trans and everything is installed, just have the truck towed to them and they'll get the driveline installed for you.
Now on to what can be the hair pulling part. if the existing ECM doesn't like the trans or transfer case, you have two options.... find a junkyard ECM that used your same engine/trans combo (giving the fact your local state will allow this, some states won't pass the inspections) or have your ECM flashed for that trans and t-case combo. If you can find someone with a real GM tech 2 and has a paid subscription to GM's tuning options they should be able to flash it, or others that do aftermarket tuning can do it also. other than this, you will need to replace your factory ECM with something like a Holley Terminator X which is fully customizable, again that also falls on how your local state is with vehicle inspections.
all in all is it worth the hassle? compare it to buying a new truck that will do everything you want... when you return home after getting sticker shocked from the price tags of a new truck on top of going into debt for as much as a house, then you can decide if it's worth the hassle of upgrading your "Now paid off truck that YOU hold the title on"
it's all do-able, it's just how much your budget is and what you want to accomplish, how it will help you, and what type of return you will get from it.
I'm thinking I will look for an 8 lug k2500 from 1988-1990 with a turb 400. I don't use my 1979 k20 much. I just want an extra cab short bed. If they would have put the front drive line on the drivers side I would use my old 79 trany and transfer case in one. It's getting hard to find a 8 lug k2500 extra cab. Thanks for the info when I went to auto mechanic school in 1975-1976 the new thing was electronic ignition. I they went to auto mechanist collage in 2001-2003. The hard part was 4 valve rice grinder heads. Valves the size of a lawn mower. I have a Kik way head shop, head surfacer, power hone, sunnen rod hone, sunnen rod heater and a valve grinder/ seat grinder in my shop. They say I'm in the stone age. The shops I worked in use 3 angle seat cutters and a cutter in the head surfacer, mine uses stones.
dbrannon79
I'm getting there!
I'm with you on that. the less electronics the better! Its hard to find someone that knows the old school ways now a days, especially in a machine shop. I actually prefer for gas vehicles the old points and carburetors over any electronics. some electronics are nice for creature comforts, but the older stuff, they just don't make the newer models that's built to last.
Will L.
Well-Known Member
Yeah, same opinion. Unless you are going to replace the engine with something mega powerful- replace the 4l60 with another one. B&M, summit, and a million other places sell them built to withstand more load than you can produce. Towing that load down the highway with a th400 that is only 1:1 is a crazy step in the wrong direction unless you tell me you only tow at 45mph tops.
Your gonna burn a ton more fuel doing that.
You are working too small a truck for what you are doing to have it last high mileage without wearing out parts.
Best transmission for your task is a manual. If you wanna swap to the 4l80 because you have an entire truck to gut for the parts- ok fine.
The factory controller will not work. Buy a stand alone for it, you’ll be 100 hours ahead.
Your gonna burn a ton more fuel doing that.
You are working too small a truck for what you are doing to have it last high mileage without wearing out parts.
Best transmission for your task is a manual. If you wanna swap to the 4l80 because you have an entire truck to gut for the parts- ok fine.
The factory controller will not work. Buy a stand alone for it, you’ll be 100 hours ahead.