Doesn't seem reasonable. "Extra 20+ HP loss" compared to what?
89 C 1500 with a 400 trans from factory??
- Thread starter TQS335
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
Insert Quarter
I'm Awesome
From what I've read and understand, (a 3L80 is 3 speeds, L-Longitudinal, and 80 for 8000gvw, 4L80 is 4 speeds and E is for Electronic) when choosing a transmission for a particular application the choice is based more on Gross Vehicle Weight and what the vehicle is going to be used for, not necessarily what engine is in front of it.
454cid
Sooper Pooper
GM put the NV4500 behind the 4.3L, too.
stutaeng
I'm Awesome
I don't know anything about the square body generation, but where they perhaps the so-called "Heavy Half" trucks? As I seem to recall or guess, those only came in long bed version?
The heavier duty tranmissions always were standard on 8 lug trucks with higher GVWR... independent of engine size. I'm talking on the GMT400, but that rule obviously doesn't hold on the very early GMT400... again I think it's because they mix and match parts from outgoing generation so they can sell complete trucks. And it seems those trucks were more like for work or fleet sales anyways.
Maybe it was different on the square body?
sweetk30
c3500-HD
Sorry forgot to say a th350 . . Not sure what a 700r4 is in this comparison.
And th400 suck for shifting stock . There all the way in 3rd by about 22mph . I had my governor modified to let it hold out a bit more and did a shift improving kit and both helped a lot .
They are nice and beefy but there power hogs .
I still think it's unlikely that they take "20+ hp" more than a TH350. They've got more rotating weight than a 350, they'd take more power to accelerate--but at steady speed or slow/moderate acceleration, I bet the difference is minimal--and nowhere near 20 hp.
Last edited:
I put an adjustable vacuum modulator on the TH400 in my Jaguar. It's one of the few parts that's still $20 cheap.
TCI Auto 350001 TCI Transmission Vacuum Modulators | Summit Racing
Free Shipping - TCI Transmission Vacuum Modulators with qualifying orders of $109. Shop Automatic Transmission Modulators at Summit Racing.
Nad_Yvalhosert
I'm Awesome
Sorry buddy, not completely true. I bought a light duty k2500 as a donor truck a couple years back. 14 bolt 6 lugger, 305/3L80 (turbo 400), 7200 GVW. Still running the 14 bolt and the heavier torsion bars in my '00 Yukon Denali
someotherguy
Truly Awesome
My point is that the 3L80 was an HD transmission which is default in an 8 lug truck; a 6 lug would not by default come with one. The overwhelming majority of "light duty" 2500's came with 700R4/4L60/4L60E transmissions. There are NO 8 lug GMT400's that came from the factory with a light duty transmission.
The very fact that this thread exists is proof already that there's no dead-set rule on what truck the 3L80 *could* come with.. buddy
Richard
stutaeng
I'm Awesome
I do agree that the heavier transmission does take more "oomph" to operate, (otherwise the law of physics don't apply, right?) but I don't think it would take that much HP either.
Here's what Jake's Performance has to say about the subject:
"What about HP loss or consumption?
The 4L80E will theoretically consume more HP than a 4L60E or other lighter duty transmission. It has a positive displacement pump as opposed to a variable displacement, it is heavier, has more rotating mass, more clutch drag, and on the surface would seem to “eat” HP. The biggest loss would seem to come from the heavier rotating mass. However what is widely misunderstood is that yes it’s heavier, but that alone doesn’t cause more power loss. Remember an object in motion tends to stay in motion unless acted upon by another force. So unless there is more friction involved, a heavier rotating mass doesn’t take any more HP to maintain the same speed as a much lighter mass. It DOES take more power to accelerate or decelerate the heavier mass. So what this means to the average enthusiast is the faster your car, the more power the transmission will consume. This applies to all transmissions. Power loss through the transmission will increase the faster you accelerate it. Our testing has shown that you will not see any significant power loss in a 11, 12 or 13 second combination. They simply aren’t accelerating fast enough that the rotating mass really comes into play. As you get into the low 10 second ¼ mile times, you may start to see some differences between a lightweight transmission and a heavier one. The thing to remember is, typically the lighter duty transmissions become a maintenance item at these power levels. More frequent rebuilds and failures. So for a small loss of power often equating to less than .05 second in Elapsed Time in the ¼ mile, you gain reliability. Unless you are racing for a record attempt where hundredths of a second are crucial, reliability is usually a more important factor."
Source: http://www.jakesperformance.com/4l80-faq/
Also something to mention is that the TH350/TH400/4L80e all have pretty low 1st gearing (around 2.50) compared to the 700R/4L60/4L60e (3.06.) I bet that's probably what most folks think is the cause of power loses when you compare the 2 side all things being equal on a side-to-side comparisons from a drivability standpoint.
For reference, the similar heavy duty transmissions of the era from competitors are also around the 2.5 mark for 1st gear (4R100 = 2.71; 47RE = 2.45).
