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Transmission Upgrade Needed with 100 BHP Power Upgrade?

jcn7vc

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jcn7vc Enthusiast

jcn7vc

Posted
Posted

So I have been driving my '08 Sierra for five years now and really enjoy it. Since it is out of warranty, I decided I will do a full power upgrade with Supercharger, exhaust, headers, and custom tune to bring it up to 450 bhp. The installation will have a warranty associated with it, and a transmission upgrade was not recommended by the company that is going to do it.

 

I have been wondering if I should also do a transmission upgrade anyway. What's the risk in running that much power through the tranny on the '08 SLT Z71 w/ towing package? Would it add substantial cost to upgrade to a tranny that has to handle that?

 

Thanks for the help people!

Chris Senior Enthusiast

Chris

Posted
Posted

An 08 SLT would have the 4L60E if it was a 5.3 and the 4L70E if it was the 6.0

 

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Chris Senior Enthusiast

Chris

Posted
Posted

I'm at approx 400 bhp on my 60E and a servo upgrade. I need to do mine before I go farther. Look at finish line transmissions. They have a wide range of transmissions for different power levels.

 

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Chris Senior Enthusiast

Chris

Posted
Posted

Do not make more power than me on your stock trans. I'm pushing it. Spend the money even if only for peace of mind

 

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ATMINF Enthusiast

ATMINF

Posted
Posted

If you can upgrade the trans to a 4L80E. The entire 700r4,4L60/60e/65/70 trans are only okay trannys. You have to remember that besides the power, the weight of a 5500-6000lbs truck hammers these transmissions. Yes a 4L80e is going to cost more up front, but you will have one hellva strong transmission that can take some abuse.

oldscsc Enthusiast

oldscsc

Posted
Posted

Do a stout build on your 4L60E. Upgrading to an 80 is more of a pain than building a 60, plus if you want speed, the 60 is the clear winner. (Lighter, less parasitic loss, steeper first gear).

00Silverado4x4 Senior Enthusiast

00Silverado4x4

Posted
Posted

Do a stout build on your 4L60E.

 

I like this idea. Eventually I would like to do this with mine, even if I don't do anything else to the engine. I use AND abuse my truck and I don't need to the trans giving out in the middle of me doing something crazy...like off roading.

music Senior Enthusiast

music

Posted
Posted

I have zero experience w/ it, but have read and thought about it a good bit. I've considered using SC on mine for towing (well, really... just a fun project). Everything in the driveline is designed/built for the stock hp/torque, and the stock tuning is set to protect components too. The motor appears to handle a reasonable amount of boosted compression/air/fuel/power, without throwing a rod. The transmission and axle gears are going to be pushed closer to their margins, especially if someone is doing a bunch of 4wd launches, or crazy "racing" stuff like that.

 

My opinion, for what little it's really worth, is to run everything "as is" to begin with. But, and it's a big but, I would tune the torque management and shift parameters to be mild. That's the opposite of "racing" parameters, with quick shifts, and no TM. What I would want (again, for towing), would be smooth, quick shifts, without hitting the gears with huge torque differentials (redline to 3500 rpm shift is a huge amount of torque to dissipate).

 

My 2 cents... and that's about all I have.

Gurrzt Enthusiast

Gurrzt

Posted
Posted

I have a performance vehicle (2001 Z28 (Sara)) and I had a 3600 2.5STR stall installed coupled to my 3.73:1 rearend gears. I upgraded parts of my transmission (4L60E) with a "TransGo" transmission kit, and a "Superior" race grade servo. I suggest you do some sort of upgrade, AND ALSO DELETE YOUR TORQUE MANAGEMENT.

 

You will also need to consider an upgrade to your "flexplate" to a "SF29" race grade plate with grade 8 bolts to hold the TC as the GM units are weak to start with.

 

Good luck with your modifications.

ATMINF Enthusiast

ATMINF

Posted
Posted

I have had my 4l60e trans built up in my 1995 supercharged z28, and for that car approx 3500lbs it was fine. Any truck 5500-6000lbs with a built motor will push a 4L60. So if you really want reliability a 4L60 is not where you want to look. But if you are intent to do a 4l60, look a getting a better sunshell, increase the line pressure, upgrade the 3rd and 4th clutch packs, and get the computer reprogrammed to understand the upgrades. Good luck. Just my 2 cents.

  • 3 weeks later...
ATMINF Enthusiast

ATMINF

Posted
Posted

Not sure if you have a 6 speed or the 4 speed? If you have the 6 speed it is the 6L80 trans, if its a 4 speed its a 4L60 series trans.

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