Has anyone swapped an 8.1 L into a GMT400?????????????????

[496BBC]

About you want to use your stock transmission so you can yuse your stock transfercase. That makes zero sense.

I've got no plans to exceed the tow rating of 6500 lbs and have no plans to put tires larger than 34" on the truck, its my daily driver.

The 5.0 is at 200000 miles and getting tired so I'm looking to do something about that issue.The truck is in great shape and really like this body style over the newer trucks. I don't really want to put another 5.0 in it so I'm looking for factory dependability along with a little more power. I want the swap to be with parts from the same era truck (GMT400) so that the factory parts are available. Not looking to increase performance to a level that would require aftermarket parts just a good factory install that will do the job. I am partial to BB's as I do have a vette with a 496 (old style) and have had a few trucks that I swapped BB's into.

To me it is easier to keep the factory correct pats to the truck and have them built to handle the power if needed.

It seems with TQ management in play and not exceeding the limits of the truck the parts should live as long as they are in good shape.

Maybe I'm wrong and if so I'll deal with it then, I'm the only one that drives this truck and I don't dog it.

Neal

 

[gmcyukondriver]

The corvette you mentioned may have higher power numbers with the 4L60e, but it doesn't have one big thing that the truck has....weight. After doing months of research, I decided that 4L60e transmissions are merely satisfactory in completely stock trucks with small-block engines. However, if you're planning on building up a 4L60e for anything more, I think you should just save yourself some future headache and just plan on a 4L80e swap.

I did the swap back in March. I found a used transmission, had it rebuilt with a transgo HD2 shift kit installed at the same time. It's been great. I went with the 4L80e because of the supercharger and because of future plans. If you only plan for what you have right now, then the minute you decide to exceed or improve your plans (i.e. make more power or drive it harder), then you're going to wish that you had just done the small amount of extra work to begin with. If I were you, I would find a 91-93 truck being parted out, and scavenge the 4L80e transmission and transfer case from that.

Someone with more knowledge may be able to chime in (I'm a 2wd guy), but you would want to make sure that you could control the t-case. The trans can be updated with a new wiring harness ($40) and newer shift solenoids instead of the stock force motors that came in those early 4L80e's. The reason I suggest the earlier years, is because I was told by the transmission shop that the earlier years, with the trans cooler lines BOTH up front on the case, cool the transmissions better. They said that later years, with one line up front and one line in the back of the case, tend to burn up the 4th gear clutches a little more quickly for some reason. Maybe it's not a big deal, but that's what I was told.

 

[496BBC]

The corvette you mentioned may have higher power numbers with the 4L60e, but it doesn't have one big thing that the truck has....weight. After doing months of research, I decided that 4L60e transmissions are merely satisfactory in completely stock trucks with small-block engines. However, if you're planning on building up a 4L60e for anything more, I think you should just save yourself some future headache and just plan on a 4L80e swap.

I did the swap back in March. I found a used transmission, had it rebuilt with a transgo HD2 shift kit installed at the same time. It's been great. I went with the 4L80e because of the supercharger and because of future plans. If you only plan for what you have right now, then the minute you decide to exceed or improve your plans (i.e. make more power or drive it harder), then you're going to wish that you had just done the small amount of extra work to begin with. If I were you, I would find a 91-93 truck being parted out, and scavenge the 4L80e transmission and transfer case from that.

Someone with more knowledge may be able to chime in (I'm a 2wd guy), but you would want to make sure that you could control the t-case. The trans can be updated with a new wiring harness ($40) and newer shift solenoids instead of the stock force motors that came in those early 4L80e's. The reason I suggest the earlier years, is because I was told by the transmission shop that the earlier years, with the trans cooler lines BOTH up front on the case, cool the transmissions better. They said that later years, with one line up front and one line in the back of the case, tend to burn up the 4th gear clutches a little more quickly for some reason. Maybe it's not a big deal, but that's what I was told.

Need to find out what is involved in swapping the 60e to the 80e in the 4x4,

thanks Neal

 

[gmcyukondriver]

On mine, it was simply swapping a couple wires in the harness (4L80e's have two Speed Sensors), but my 4L60e had a PWM solenoid that wasn't on the 4L80e, so we just moved those two wires in both connectors. Basically wired like the factory would have, then had to have a custom chip burnt.

A 4L80e is also longer, so the transmission support had to be moved back, but it would probably be easier for you, since I'm assuming your frame would accommodate the movement a little better than mine did. Also, since it's longer, your front driveshaft will have to be lengthened and your rear driveshaft will have to be shortened. It's going to be a lot of work, and probably cost more than a $1500 rebuild on a 4L60e. Mine was probably in the 3k range by the time I bought the trans, had it rebuilt, had it installed with all the custom work to the mount and rear driveshaft, and then had the custom tune burned. But in the end, I'm glad I did. More peace of mind. If you honestly think a shop can do the same with your 4L60e, then don't let us stop you, but everything I ever read said that a stock 4L80e will outperform and can handle more power/torque than most built 4L60e's. And there's plenty of upgrades for the 80e to make them even better, in case you ever go crazy.

 

[someotherguy]

Richcard those were the pictures I found also, is that the 0411 computer on the fender?

If those are the exact pictures you found, those are pictures I put together from old online ads. As far as the PCM, it sure looks like it; it's definitely an LS-style PCM and the 8.1 is a coil-pack engine, so it makes sense. It's definitely not the old style PCM that you would find with the Vortec 7.4 from 2000 and prior.

The 4L60E can be built to handle the 8.1 for around $1500 with 2 year unlimited millage warranty which from what I can find is less then the cost of replacing it with a 80e and HD transfer case.

I don't know about it being truly capable of lasting behind that engine and moving the weight of a truck around, for only $1500. There are more than a few weak links that come up in the 4L60E once you start really pushing the limits; it needs more than just a Beast sunshell and some extra clutches. Besides, depending on leaving torque management fully in effect instead of tuning some percent of it out, is going to leave you less than satisfied with the 8.1. They're powerful engines but fairly neutered off the line in stock tune.

Richard, from the pic's it looks like the GMT400 cruise control unit above the booster is being used, I thought I had read that the only way the 8.1 came was with electronic throttle but could be converted to cable.

I don't know how they handled it, but from my perspective, I don't see the old style cruise unit on the firewall in any example of 8.1-equipped 3500HD that I can find. I'm tempted to say that even though it's in a GMT400, it's DBW. Look closer at that firewall...I don't see a cruise unit...nor do I see a regular throttle cable going to the throttle body, for that matter.

I haven't been up close and personal with an 8.1-equipped 3500HD but my dad just sold one that was his former shop truck, replaced it with a Duramax...because the 8.1 was gutless pulling hills with a loaded equipment trailer.

Richard

 

[BoxerPitMix]

Looks to me like they're DBW
http://www.purplewave.com/cgi-bin/mnlist.cgi?100615/3192/21

You must be registered for see images

 

[496BBC]

If those are the exact pictures you found, those are pictures I put together from old online ads. As far as the PCM, it sure looks like it; it's definitely an LS-style PCM and the 8.1 is a coil-pack engine, so it makes sense. It's definitely not the old style PCM that you would find with the Vortec 7.4 from 2000 and prior.


I don't know about it being truly capable of lasting behind that engine and moving the weight of a truck around, for only $1500. There are more than a few weak links that come up in the 4L60E once you start really pushing the limits; it needs more than just a Beast sunshell and some extra clutches. Besides, depending on leaving torque management fully in effect instead of tuning some percent of it out, is going to leave you less than satisfied with the 8.1. They're powerful engines but fairly neutered off the line in stock tune.

I'll give the trans shop a call and see what they say about their Stage 2 4L60E as far as the 496 and its power range.


I don't know how they handled it, but from my perspective, I don't see the old style cruise unit on the firewall in any example of 8.1-equipped 3500HD that I can find. I'm tempted to say that even though it's in a GMT400, it's DBW. Look closer at that firewall...I don't see a cruise unit...nor do I see a regular throttle cable going to the throttle body, for that matter.

Looking in the third picture there is a black box mounted just above and to the right of the brake booster on the fire wall, that's where the cruise box is mounted on my 96. I went back and looked at the parts list and the cruise is not listed for this style truck and all the throttle bodies are DRW so it can't be the cruise box on the firewall that i see.

I haven't been up close and personal with an 8.1-equipped 3500HD but my dad just sold one that was his former shop truck, replaced it with a Duramax...because the 8.1 was gutless pulling hills with a loaded equipment trailer.

Richard[/QUOTE

 

[496BBC]

I used the quick reply so your (Ricahrd) text is not wrapped,

 

[496BBC]

Boxerpitmix, I looked in the parts catalog and you are correct they don't offer the throttle body in a DBC setup.

 

[496BBC]

Ran by the salvage yard to look at the two 8100 they have, one is in a 01 3500 Savana van and the other is in a 01 silverado truck. The van has the high mount AC compressor so that one will work with the GMT400. The van came from a church that used the van to transport people to and from church (I called the church and talked with the person that drove the van). It was wrecked recently so the insurance comp got it and sold it to the salvage yard. The van has a digital dash so I can't validate the millage, the guy I spoke with at the church didn't know the exact millage but said it did have somewhere over 100000 on it, he also said they didn't have any issues with it mechanically and he didn't remember it using oil to any extent.

Need to verify that 0411 will work with this engine and check to make sure I can get the harness that I located on the net, if so I may pull the trigger on the 8.1.

Neal