Gm Vortec 8.1L?

[me32]

It's an updated big block based on BBC architecture, not LS architecture.

Cylinder heads are not bad but the exhaust manifold studs are small (M8x1.25) and break often. I was always replacing them on a 3/4 2005 Suburban i had years back.

TBH, i wasn't real impressed with the power that truck made.

What basic things could you do to make more power and maybe gain mpg

 

[me32]

Bite the bullet and pay a little more for the Cummins. Fuel mileage alone will be roughly twice what you’d get with the 8.1 and while there are a few irritating things with the Ram, they’re relatively easy and inexpensive to correct.

03-05 will they make all the power you’d need with HPtuners and don’t have nearly the electrical gremlins. If you want to go wild on mods the 06-07 are where you want to be to use EFILive though you have the TIPM which is a double edged sword.

The 48re is a badass trans when built but doesn’t have that nice OD spread like 5th in the Allison though for towing but it will still pulls awesome with that low end torque.

03-05 trans are not friendly to high temperature climate. Definitely needs to be built.

 

[Junior00]

03-05 trans are not friendly to high temperature climate. Definitely needs to be built.

Technically 04.5-07 were all the same. Late 03 & early 04 still had the tv but were just as capable. All were far better than the 5 pinion 47 though.

I don’t believe a single transmission on this planet lives under high temps tbh. The newer formulations like +4, tes-295, 468 & now 668 make a huge difference compared to the old atf blends though.

A stock 48re is stout, we had one go almost 400k pulling 11-14k daily. If you’re wanting to hotrod though it must be built…input, converter, additional clutches and addressing the vb at minimum.

 

[gimmie11s]

What basic things could you do to make more power and maybe gain mpg

The basics... high flow exhaust, CAI, and a tune would give almost 50 hp on these. MPG will never be great and the aftermarket never really took off for this motor, but its a stump puller, thats for sure.

Technically 04.5-07 were all the same. Late 03 & early 04 still had the tv but were just as capable. All were far better than the 5 pinion 47 though.

I don’t believe a single transmission on this planet lives under high temps tbh. The newer formulations like +4, tes-295, 468 & now 668 make a huge difference compared to the old atf blends though.

A stock 48re is stout, we had one go almost 400k pulling 11-14k daily. If you’re wanting to hotrod though it must be built…input, converter, additional clutches and addressing the vb at minimum.

48re was a great trans that can be built to hold stupid power. Downfall is it lacks an additional OD gear. I had an 06 (last great year IMO) with factory 4.11 rear end and that ****er was out of breath around 70 mph lol.

 

[gimmie11s]

I had a same year 6.0 2500 and it felt slow to me from a dig. The 8.1 roasts tires.

I have the oppossite opinion. We had an 05 3/4 Suburban with the 8.1 and 3.73s. We also have an 02 3/4 Suburban with the 6.0 and 4.10's and the 6.0 truck will wipe the floor with the 8.1. The higher rpm nature of the LS motor vs the big block along with 4.10s makes a sweet combo.

Gearing makes a huge difference in this generation gas vehicle. Huge.

 

[Tractorman]

I had a Dodge of that vintage. Engine was fine, trans was ok after it was built. Otherwise, rest of truck was hot garbage.

 

[RedRocketMike]

I have the oppossite opinion. We had an 05 3/4 Suburban with the 8.1 and 3.73s. We also have an 02 3/4 Suburban with the 6.0 and 4.10's and the 6.0 truck will wipe the floor with the 8.1. The higher rpm nature of the LS motor vs the big block along with 4.10s makes a sweet combo.

Gearing makes a huge difference in this generation gas vehicle. Huge.

Definitely does. That's mostly why I like the 8.1 Silverado over the 6.0. The 4L80 has a ridiculously long first gear. The Allison 1000 in the 8.1 trucks has a much more aggressive first.

Although, if you dig around old forum posts there is talk about the 8.1s in the Suburbans/Yukons having a less aggressive tune than the trucks, in addition to the gearing disadvantage.

 

[gimmie11s]

Definitely does. That's mostly why I like the 8.1 Silverado over the 6.0. The 4L80 has a ridiculously long first gear. The Allison 1000 in the 8.1 trucks has a much more aggressive first.

Although, if you dig around old forum posts there is talk about the 8.1s in the Suburbans/Yukons having a less aggressive tune than the trucks, in addition to the gearing disadvantage.

Interesting! I'd not heard of that tune difference between the sub's and trucks. Would make sense because that 8.1 sub we had was kind of a dog. Definitely didnt have the BBC "hit" right off the pedal you expect.