4L80E to NV5600 Swap?

[Sean Frawley]

Hello,

My 4L80E seems to be approaching the end of its life cycle. First gear is starting to lag and does not downshift in time when accelerating.

My truck is a 2000 GMC K2500 with a 5.7L V8. It has roughly 167,700 miles on it.

I'm wondering if it is possible to swap out my 4L80E for an NV5600 6-speed manual transmission.
I know it's a large undertaking, but I'm going to try and have a local performance shop do the swap if at all possible. If not, I'm just going to have them put in an NV4500 5-speed instead.

Also, what is recommended for this type of job, new transmission or rebuilt?

Thank you, and please let me know what you think. This truck is my daily and I need answers soon!

 

[Christian Steffen]

Hello,

My 4L80E seems to be approaching the end of its life cycle. First gear is starting to lag and does not downshift in time when accelerating.

My truck is a 2000 GMC K2500 with a 5.7L V8. It has roughly 167,700 miles on it.

I'm wondering if it is possible to swap out my 4L80E for an NV5600 6-speed manual transmission.
I know it's a large undertaking, but I'm going to try and have a local performance shop do the swap if at all possible. If not, I'm just going to have them put in an NV4500 5-speed instead.

Also, what is recommended for this type of job, new transmission or rebuilt?

Thank you, and please let me know what you think. This truck is my daily and I need answers soon!

I would imagine that it is possible with enough money, I'm sure it will be spendy having a shop do it.

Have you looked at the fluid in your 4l80e? Has it ever been changed? I find it hard to believe that a 350 can wear out a 4l80 in 170k, I have 230k on mine behind a big block with lots of towing miles and it shows no signs of giving up.

When you say it doesn't downshift in time, do you mean you floor it and the truck stays in the current gear for too long?

 

[Sean Frawley]

I would imagine that it is possible with enough money, I'm sure it will be spendy having a shop do it.

Have you looked at the fluid in your 4l80e? Has it ever been changed? I find it hard to believe that a 350 can wear out a 4l80 in 170k, I have 230k on mine behind a big block with lots of towing miles and it shows no signs of giving up.

When you say it doesn't downshift in time, do you mean you floor it and the truck stays in the current gear for too long?

Thank you for the response.

I had the trans serviced when I bought it at 132K and it seemed fine. When I looked at it this past week the fluid was good.

Whenever I have to floor it, it takes about 5 seconds for first to engage, and by that time it has to switch back to second. In the amount of time I’ve used the truck, I’ve had to use first in 4Hi and 4Lo quite a bit.

 

[Biggershaft96]

Itd be alot of high dollar custom stuff like bellhousing, driveshafts, probably have a hell of a time finding a clutch thatll work. Sounds like a pain when you can drop a nv4500 with off the shelf parts.

 

[Christian Steffen]

Thank you for the response.

I had the trans serviced when I bought it at 132K and it seemed fine. When I looked at it this past week the fluid was good.

Whenever I have to floor it, it takes about 5 seconds for first to engage, and by that time it has to switch back to second. In the amount of time I’ve used the truck, I’ve had to use first in 4Hi and 4Lo quite a bit.

Interesting, no error codes? If it is indeed bad then a nv4500 would be the easier manual swap route. You will need custom tuning to do that though. Swapping in a used 4l80 would be the easiest route.

 

[JScott23]

It's doable. But first off. The NV5600 while a six speed isn't a double overdrive transmission, therefore the only difference between it and the NV4500 is the jump between 2nd and 3rd gear. In comparison to the NV4500, the NV5600 is much more expensive, and honestly, in my opinion (especially with a 350), it's just not worth the added cost.

I would go the NV4500 route, since it was available in these trucks from the start. There are plenty of prior write ups on this, so just search and leverage prior work.

Aside from purchasing the trans, bellhousing, clutch, pedal assembly....

The driveshafts are going to be different as the NV4500 is a little shorter than the 4L80E. The rear driveshaft will work, but I would personally have it lengthened as it leaves 1/2 the spline exposed once you mount it up. Front driveshaft will not work and you'll have to have a custom one made. I can't remember if the crossmember was the same, or not, I believe it was. But it will definitely need moved.

We did this swap on a buddies K2500 CCSB a few summers back, knocked it out in a weekend. he left the stock rear driveshaft alone and drove it no problem. 5 speed definitely is a little nicer for towing, but I'd like to say he spent around $1500-2000 to do the swap. And that was us doing the work ourselves.

 

[Chewy1576]

A 5600 won't mate to a 350 without a custom adapter plate or bell housing. There may not be an input shaft or clutch/pressure plate available that fits a GM flywheel either, so that will need to be addressed also.