454 tbi with 4l85E swap into c1500 350tbi

[Christian Steffen]

Thanks. I forgot to note the 4L80e also came behind the 15,000 GVWR GMT-400 3500HDs. Some motorhomes also had them. Not sure if those were stock or not though.



So perhaps the largest advantage of the Allison over the 4L85e is the additional gears then? I mean, you can't really compare them directly, as I imagine they are different designs. I don't know anything about Allisons, but I thought they were 5 or 6 speed on that generation? Sorry OP for derailing your thread

Imo, a 6l80 would be better for a stock to low mod gas engine than the Allison, hell maybe even with some boost on the gasser. The Allison is an awesome transmission for diesels but if you don't need the strength you're just wasting a lot of power. I've read they'll eat up to 30% in pumping losses. Strictly forum heresay, but for how strong the 6l80/90 are, there's little reason to go to the Allison for gas engines.

Also, I believe it was just the lb7 duramaxs that got the 5 speed Allison.

 

[MIHELA]

Not really. Matt Happel of Sloppy Mechanics built a turbo LQ4 LS Colorado that broke 1K HP to the wheels and ran several sub 10 second quarter mile passes at around 150MPH through a junkyard 4L80E with a TransGo HD2 kit. That was the only modification. There are lots of guys pushing stupid power through nearly bone stock 4L80Es. Additionally...









Jake's Performance is another good resource for 4L80E stuff. I'd stay far, far away from Monster.

This is true for the LS motors, but when you start talking big blocks the torque comes on low enough that you should probably think about upgrading the input shaft as well.

 

[Supercharged111]

I perceive the advantage of the Allison

This is true for the LS motors, but when you start talking big blocks the torque comes on low enough that you should probably think about upgrading the input shaft as well.

It's not just that, I think they can struggle to build enough fluid pressure at a low enough RPM? But my dually has been just fine with a load so far.

 

[Christian Steffen]

This is true for the LS motors, but when you start talking big blocks the torque comes on low enough that you should probably think about upgrading the input shaft as well.

How low of an rpm do you think it would be an issue. I can get into boost down around 2000 rpm on my truck, so far so good. I gotta imagine I'm going to kill my transmission eventually though.

 

[MIHELA]

A stock Vortec 8100 makes about 400 lb-ft at 1000 RPM. That puts a lot of strain on components. Build the motor up and its even more.

 

[Supercharged111]

A stock Vortec 8100 makes about 400 lb-ft at 1000 RPM. That puts a lot of strain on components. Build the motor up and its even more.

Mine is over 600 at peak torque. . .

 

[Christian Steffen]

Mine is over 600 at peak torque. . .

I really don't know what mine makes, but when the turbo gets to spooling it feels like driving a diesel.

 

[Supercharged111]

I really don't know what mine makes, but when the turbo gets to spooling it feels like driving a diesel.

Likely the same or better.

 

[Christian Steffen]

Likely the same or better.

I've yet to run it with my brothers tuned LBZ, but were both pretty sure I'd beat it (he's ridden in it, just haven't raced lol). His LBZ just gets 17-20 mpg while I haven't broken 14 for quite awhile, more like mid 12s, but I haven't taken it very far either.

 

[Supercharged111]

I've yet to run it with my brothers tuned LBZ, but were both pretty sure I'd beat it (he's ridden in it, just haven't raced lol). His LBZ just gets 17-20 mpg while I haven't broken 14 for quite awhile, more like mid 12s, but I haven't taken it very far either.

Meh. You're into your truck for way less than he is more than likely. I will say LBZ/6 speed Allison is high on the want list.