4L80E behind a 6BT

**77Wrecker** · 02-04-2020

I'm looking to install a transmission behind my 6bt (12v VE pump). I currently have the Tf727 that came with it.

My question is, how reliable is the 4l80e behind the Cummins? I'm aware that the swap should be straight forward, Summit Racing have all the necessary parts needed to complete the swap.

Should I rebuild the Tf727 or should I invest in the 4l80e swap?

Where I'm from, Dodge transmissions are virtually nonexistent (47rh/47re/48re), otherwise this would have been the preferred choice.

The truck will be used mainly for highway driving and I'm only looking to make 400-500 hp out of it. No towing or hard launching. Maybe a P pump swap later down the road.

Any input or feedback is highly appreciated.

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**Aj Grubb** · 02-04-2020

The 4L80 is a stout unit. But there is a reason that GM didn't even put it behind their 300hp Duramax back in 2001. Cummins engines are even tougher on transmissions than v-8 diesels because they make so much power at such a low rpm. I think there is no way a 4l80 lives very long behind a 500 horse Cummins. Bite the bullet and get an Allison if you want to make anything more than stock power.

If you leave your 12v bone stock and don't turn up the fuel the 4l80e would probably survive with the correct toque converter.

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**watersupply189** · 02-04-2020

Originally Posted by 77Wrecker

I'm looking to install a transmission behind my 6bt (12v VE pump). I currently have the Tf727 that came with it.

My question is, how reliable is the 4l80e behind the Cummins? I'm aware that the swap should be straight forward, Summit Racing have all the necessary parts needed to complete the swap.

Should I rebuild the Tf727 or should I invest in the 4l80e swap?

Where I'm from, Dodge transmissions are virtually nonexistent (47rh/47re/48re), otherwise this would have been the preferred choice.

The truck will be used mainly for highway driving and I'm only looking to make 400-500 hp out of it. No towing or hard launching. Maybe a P pump swap later down the road.

Any input or feedback is highly appreciated.

Welcome friend

2016 Ram Laramie 3500 (DRD), G56, 6.7, Rough Country Leveling, HID headlights, Morimoto LED fogs plus a whole lot more!

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**david3gen** · 02-04-2020

Welcome @77Wrecker

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**coryscummins** · 02-04-2020

We need a “VINTAGE” section.

I love those 1st gens and this sounds cool!

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**77Wrecker** · 02-05-2020

Originally Posted by Aj Grubb

The 4L80 is a stout unit. But there is a reason that GM didn't even put it behind their 300hp Duramax back in 2001. Cummins engines are even tougher on transmissions than v-8 diesels because they make so much power at such a low rpm. I think there is no way a 4l80 lives very long behind a 500 horse Cummins. Bite the bullet and get an Allison if you want to make anything more than stock power.

If you leave your 12v bone stock and don't turn up the fuel the 4l80e would probably survive with the correct toque converter.

Thanks for the reply AJ,

Any idea what's needed to complete the Allison swap (apart from the adapter, flex plate and the standalone controller)? How much would it approximately cost? Where can I find the Allison transmission other than in GM diesel trucks (lightweight diesel trucks aren't common around here), i.e which medium/heavy duty trucks came with the Allison?

I thought about that before, but I was worried I would run into having to order a complete rebuilt transmission and have it shipped overseas. (Shipping alone would cost upwards of $2K).

Thanks again AJ.

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