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GMT 900 Trucks General Discussion 2007 - 2013 Trucks | General Discussion

2010 LC9 5.3 need more torque Mod's?

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Old 11-24-2010, 12:01 PM
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Add a yank truck thruster 2600 stall, that will help with towing quite a bit. Any they are quite inexpensive, wish they were as inexpensive for the 6L80E
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Old 11-24-2010, 03:52 PM
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[QUOTE=dlt76028;4583848]I'd stick with the Doug Thorley Tri Y headers, the 2.5" collectors will help with more TQ lower.

Yes at this point I see no reason to not use the TriY header

Since you have the 6sp, I would easily go 4.10s if not a little lower, but I doubt you will be able to hold 6th gear while pulling. ]

[B]I would be very happy to have it hold in 5th in hilly terain and some wind ... yes 6th would be a stretch .maybe with tailwind


Yes will work with Justin on the tune as you say .he did a great job on my 04
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Old 11-24-2010, 04:07 PM
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Just my opinion here based on my own personal experience...

1)Longtubes do NOT sacrifice low end torque. My truck makes just as much on the low end with 1 7/8" headers as it does with the stock manifolds. That being said, I wouldn't waste your money on any sort of exhaust modifications, it won't make any difference in towing power.

2)Going from 3.42 to 4.10 gears could be mildly helpful, but I wouldn't call it any sort of major enhancement for towing. It won't be like going from a small block to a big block, but it will help you maintain speed up hills and whatnot without downshifting. That seems to be a concern of yours.

3)Depending on what wheel/tire combo came on your truck, I'd put the smallest wheels that will fit over the brakes. Wheel/tire weight can have a significant impact on power to the ground

4)The only modification to my truck that enhanced towing power was a swap from a 4.8L to 6.0L. The 4.10s, longtubes, CAI, Yank torque converter, etc. all enhanced my mid to top end power, but did nothing for the towing RPM range. So essentially, you may just need to accept what you have now.
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Old 11-24-2010, 05:15 PM
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My experience is that the gear change will make a major difference... in my 04 5.3 went from 3.42 to 3.90 ... I never had an issue geting the load moving etc it was torque availalble at highway speeds going to 3.90's allowed me to pull in OD except in headwinds .... mileage improvement and far less trans downshifting

In the 6spd witha 4-1 low gear the 3.42 will be fine to get the load going but once in 5th and 6th the rpm will be below 2000 rpm and it seems that the lowest rpm the 5.3 has any real pulling power is 2300-2500
If you have towed alot with a 5.3 with an enclosed trailer up in the wind you would find 200 rpm can make a big diff in keeping the truck in OD and not hunting up and down for a gear .yes a bigger engine would have the torque at lower rpm hence not as much need for lower gears
but not in a 5.3

So I think a change to 4.10 will make a major change and allow it to pull in the sweet spot rpm in 5th ...... effective gear will be 3.49 .....effective gear with 3.90 in a 4 spd in OD was 2.73 3d was 1-1 3.90 a little too steep for decent mileage as cruise was around 2800 ........ so unless I am missing something it will be a big improvement but still keep my cruise rpm undr 2600 for good mileage .my towing mileage was always best around 2200 at 18-2000 it was worse cause it was lugging ... I would luv to hear from someone who is towing 7-8000 lbs with 4 10 and a 6spd

Headers .....help or not for towing ?

I'm no expert on these 5.3 motors that why I am asking here for all your experience with these motors ... but I have alot of experience with BBC race motors and have spent alot of dyno time and I can tell you header tube size and collector diameter and length have have a big impact of torque output and the rpm it peaks at as do tailpipe diameter .so not so sure I am ready to accept that a well designed headr could not make more torque down in the 2000-3000 rpm range than stock exhaust manifolds ( unless someone here tells me the 5.3 manifolds are extemely well designed for max torque out put) remember these are a TRI Y design not a 4 tube .......This only a 325 ci motor for tow rig with max rpm 5k I would say no to 1 3/4 4 tube being the right size for this application even in the midrange , maybe possible with a very small and long collector ..most off the shelf 1/3/4 header have a 3" or bigger short colector I beleive ........... maybe the 5.3 needs a 1 3/4 header and 1 5/8 is too small but up to say 5k they should be fine then the 1 3/4 will pull ahead ..my experience when in doubt go smaller for a street vehicle
I just have my butt dyno to tell me how they felt in old truck no real hard facts ...... I felt they did pull harder from idle to 5 k than the stock exhaust manifolds ..............

Not sure I get how a looser converter could help with towing unless for initial takeoff or passing ........ someone help me withthat I'm open if it makes sense
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Old 11-24-2010, 05:39 PM
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what speed do you like to tow at and what size tire do you have? Heres a good website to play with the numbers for your gears. http://www.csgnetwork.com/multirpmcalc.html

I plugged in 31" tire and 65mph, and 4.10s would have you at 2461 in 5th gear, and 4.56s would have you at 2143 in 6th gear.

6l80 info.
http://en.wikipedia.org/wiki/GM_6L80_transmission

and your right, stick with the stock converter for towing. and it sounds like you know alot more about headers then alot of the people here. stick with your first thought.
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Old 11-24-2010, 08:05 PM
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[QUOTE=dlt76028;4584027]what speed do you like to tow at and what size tire do you have? Heres a good website to play with the numbers for your gears. http://www.csgnetwork.com/multirpmcalc.html

I plugged in 31" tire and 65mph, and 4.10s would have you at 2461 in 5th gear, and 4.56s would have you at 2143 in 6th gear.

Thanks for that link, great ... did not realize a calculator for the new 6 spd ....I have 31.6 tires so those good numbers to lookat ...... hmmm 4.56 looks tempting ....... 1 st gear would pretty short


I will play with calc ...... one thing I think I know is the 5.3 needs to be at 2200 to hold a gear with any inlcine or wind ....... so might make sense to gear for that rpm in 5th ......holding in 6th wont happen much ....unless I went 4.56 ............... or I can get a little more torque from the 2010 LC9 5.3 than I get fom my 04 5.3

6l80 info.
http://en.wikipedia.org/wiki/GM_6L80_transmission




Good stuff thankyou

Last edited by CDN SS; 11-24-2010 at 08:11 PM.
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Old 11-25-2010, 02:42 AM
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all this yapping ,my first question is does thorley make headers for the GMT 900
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Old 11-25-2010, 06:58 AM
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Originally Posted by gonzo 6.0 View Post
all this yapping ,my first question is does thorley make headers for the GMT 900
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Old 11-25-2010, 10:19 PM
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I believe that going from the 3.42s to 4.10s will surprise you on the amount of additional torque it creates, since the gears are something you plan to change I would do them first.

Not terribly expensive to do and you are going to add more torque to the rear wheels with the gear swap than all the other mods you are thinking about combined.

I have 4.11s behind my 6L80E and love them.
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Old 11-26-2010, 09:19 AM
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Originally Posted by double047 View Post
I believe that going from the 3.42s to 4.10s will surprise you on the amount of additional torque it creates, since the gears are something you plan to change I would do them first.

Not terribly expensive to do and you are going to add more torque to the rear wheels with the gear swap than all the other mods you are thinking about combined.

I have 4.11s behind my 6L80E and love them.


Thanks for posting ...... good to hear from someone who has the 6 spd and 4.11 ... hows non towing mileage ? ..when I went to 3.90 city mileage went up and highway about the same if I stayed at 65 ........above 65 lost mileage over the 3.42's
........Yes the math does not lie as you say the the gears will improve the useable torque alot ...I played with the calculator link posted and with my tire size and 65mph 4.10 will put me at 2400 in 5th 1890 in 6th ........ in my old 4 spd OD truck with 3.90's in a headwind it would not stay in OD ...1900 ..not enough power at that rpm and 3rd was too high at 2700 mileage went in the tank ..so the 6spd with 4.10 will alow give me 300 rpm more in 5th ....even if I dont make any more torque in the 2010 5.3 over the old truck that extra 300 rpm will keep it in 5th and at 65 so wont be downshifting etcetc ....that great .in flats and no wind I will definitey be able to cruise in 6th at 1890 ....... thats the same rpm my old truck ran at 65 in OD ........I can see now how effective that 6spd is ...plus stronger than th 4l60e


I was never expecting some major mod that would give a huge torque increaes ( outside of a boost) .just wanted to know if I had missed any key item for these 5.3's that his site knows well

OK apologize for the yapping but if you dont ask you dont learn ......... and yes the DT 310-y -c headers fit the new 900 trucks
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