5.3/t56 into a 72

[BIGBLU 72]

So I'm really interested in swapping a 5.3 FI engine mated to an LS t56 in to 71/72. Bottom line is my 04 Silvy SS is eating me alive in fuel. I love te 67-72 body style so I figured that it would be a good alternative. But I have some questions?
1.will I get 20+ mpg high way w 3.73 gears? Will I need taller or Lower if not?
2. I want to do this CHEAP as possible, so can I use my stock gas tank?
3. Anyone have any tips with wiring, the 6 speed or just in general.

Prob start collecting parts then sell the SS in the spring to fund the build
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[Clyde65]

1. dont count on it. however, I would think if you tuned it right, it should get 18.
2. Yes you can, an external pump/filter, use a DBW motor with the returnless fuel rail. Custom Classic trucks magazine did an article about this ( maybe it was Classic Trucks mag)
3. If your going to need to purchase the stock harness, then dont, buy an aftermarket one, youll spend some $ but youll have what you need and nothing else.

If your really mechanical, have a couple friends and of course all the parts, you can do the swap real fast, weekend maybe. Look here on the LSx board for tips and many posts of other folks' experience and costs.

Good luck!

[dznucks]

When picking out the T-56, keep in mind that they will have different 5th/6th gear ratios. 18 mpg might be doable with 3.73's, but 4.10's would be a better bet to get in the 20mpg range. If your not going to set up a T-56 right, its not worth the time and money just to say you have a 6th gear that you cant use.

You'll need the midshift kit unless you are going with custom bucket seats. The midshift kit is not difficult to install yourself if you have any mechanical ability. While your in there, you may as well swap out the 3/4 shift fork, install billet syncro keys, and replace any worn bearings and seals.

[BIGBLU 72]

I had wondered about the 4.11s bc of the super deep 6th. I plan on using seats out of a 03-07 Silverado and reinforcing the floor for the seat mounted seatbelts, so will I still need the midshift kit? Also with the 4.11s could I start in 2nd and only use 1st in "granny" situations? Thanks for the help bc I'd really love to do this for a daily driver soon
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[dznucks]

I am looking for a pair of the same seats, '03-'07 60/40 beanch with the flip up console. Based on the pictures i have seen, yes you will still need the midshift kit. Hurst offers several different shift levers to put the shift knob in just about any location. The T-56 has a reverse lockout, I used a shift knob with the buttom mounted on it to activate the reverse lockout.

A stock T-56 will put the shifter coming up just forward/through the hump under the bench in the 67-72's.

I am running 4.10's behind my T-56 and first gear is not granny low. Its actually perfect with 28" tall tires. Also keep in mind that tire size is a variable that you can play with to fine tune things.

You'll also have to do a hydraulic clutch, which isnt difficult. For me that was a big plus to the T-56 swap. Its a softer pedal, shorter pedal stroke, and eliminates the header issues with a mechanical clutch setup.

Check out the T-56 rebuild and midshift install in the Engine/Drivetrain FAQ.

[502ms]

Dznucks, I see that you are local...I'd love to talk to you about this swap....I have been planning this swap myself..except I am thinking the 383 motor with the t56 is what I want. I am running 3.73s, but I want the power and more gears...plus the newness under the hood
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[BR3W CITY]

I'm all for more swaps happening, but allow me to play the devil on this;

a 5.3 with stock cam and mileage-oriented tune in a lighter vehicle with the 3:73 and a tall tire (effectively making it even lower than 3:73), may net you over 20hwy, in a manual trans vehicle.... BUT

You will never make back the cost of the swap in the difference in fuel....swapping engines (or in this case, building a whole different truck), will always be an exponential cost difference.

You can do the math, but at $3.65 you can get over a thousand gallons of gas for the cost of your swap.

[Custom 68]

I have tried the T56 in my truck with 3.73 gears. I am going to swap these out to 4.?. first gear is higher (lower numerically) than a 4l60 I think that makes it hard on the clutch. With that in mind and the double overdrive I think it is a must to get a deeper gear. I was less than 1500 RPM at 65 to 70 MPH.

I think 20 is doable, I have a 5.3 turbocharged and cammed and I am shooting for 20 plus on the power tour.

You are correct, you can never make up the money in fuel savings.

[dznucks]

You will never make back the cost of the swap in the difference in fuel.

BrewCity is spot on. You have to make sure your motors power curve is going to be correct with all the gearing of the T-56 to make the best cruise mpg. It would take you a long time to make any financial gain from the swap.

custom68 I am running 4.10's with a 28.5" tall tire and I use all of 1st gear.

The factor you have to consider is the aerodynamics of the car they put these transmissions was alot better than these brick wall of trucks we drive. At the speeds needed to use 6th gear, on the interstate, the force of the air on the front of our trucks is alot greater than the comaro's and mustang it came out of. Bottom line is you need to build a motor that is going to be a torque monster off idle to 2000rpm, but not so big to be a fuel hog. The power curve of these milder stock 350's or LT/LS engines is not tuned to efficiently move a heavy truck at that low of an rpm.

The 383 will be a good motor for a T-56, but they arent the best on fuel.

[Hart_Rod]

Originally Posted by BIGBLU 72

So I'm really interested in swapping a 5.3 FI engine mated to an LS t56 in to 71/72.
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HHHHMMM LS1/T56.....I can hook you up with most everything you need....

http://67-72chevytrucks.com/vboard/s...d.php?t=554542

Let me know.

R/

[502ms]

I have started this swap. I have a GTO t56, Dirty Dingo mounts and an LQ4. I have the motor where I want it, the shifter is ending up right at the middle of the space right behind the high hump. My question is if I want to get the shifter slightly forward without doing the mid shift mount kit, what are my options?

I see there is the B&M 45052 shifter for the f-body, as well as the offset lever:
http://www.tickperformance.com/treme...y-cobra-viper/

What would you recommend? I just need about 2-3 inches forward
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[502ms]

Anyone?
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[502ms]

Well, my swap is finished.
6.0/6-speed.
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[truckdude239]

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