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Old June 9th, 2009, 01:29 PM   #1
rriggs55
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Default '95 GMC Suburban 2500, 7.4

I bought a '95 Suburban 2500, 7.4 w/ a 411 rear end. Am told it's rated for 12,000 lbs towing. I pull a 9,000 (loaded) travel trailer, and for the most part the truck pulls pretty well, though not as well as I'm led to believe it should.

A trip to NC Mem week gave it a work out climbing the Blue Ridge Mountains on 26 South to Asheville. I couldn't get it over 25 mph on the climb, and had to run the heater to keep the engine from overheating.

I had installed new Bosch Platinum plugs, new wire, rotor cap and button, radiator flush and new synthetic oil change before the trip - all of which I believe saved me from a break down. I had rebuilt the tranny last year and only have 2,000 miles on it.

I'm tossed between upgrading to a Ford Power stroke Diesel, a Dodge Cummins Diesel w/ Allison tranny or something with more towing power.

OR - doing some minor things to boost the horsepower - suggestions??

1. replacing the air scoop to the air filter with a large open air filter to allow more air flow to the carb
2. replacing the exist 2 bbl carb w/ a 4 bbl

any other suggestions or am I looking in the wrong direction??
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Old June 9th, 2009, 03:11 PM   #2
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I would check your book on the tow rating, I have almost the same truck and think it's rated for less. I have towed a 8000+ Lbs tractor and trailer and I wouldn't think it was good for much more even on levelish roads.

It's not a carb, or at least it didn't come with a carb. Should have TBI and unless you change other stuff on the engine you will not gain anything by swaping it.
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Old June 9th, 2009, 03:21 PM   #3
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I would check your book on the tow rating, I have almost the same truck and think it's rated for less. I have towed a 8000+ Lbs tractor and trailer and I wouldn't think it was good for much more even on levelish roads.

It's not a carb, or at least it didn't come with a carb. Should have TBI and unless you change other stuff on the engine you will not gain anything by swaping it.
95 should be multiport.

that 9K travel trailer would drag you down in those mountains, I've pulled those grades and its nothing to sneeze at, although you shouldn't be overheating and might want to check your fans, the fan clutch or the electric, make sure they are kicking on, stuff like that. The only way you are going to pull those hills over 60 is with a 1ton diesel, true, so its up to what you want to invest. The last thing you can check is for intake manafold leaks and run a compression test and see if the motor is just warn out... how many miles on the truck?
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Old June 9th, 2009, 03:27 PM   #4
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95 is TBI
96-98 is Vortec
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Old June 9th, 2009, 03:30 PM   #5
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95 is TBI
96-98 is Vortec
GM took a while to get their truck motors to EFI, my moms 95 Jimmy was multiport, and I had an 89 ford that was multiport, and my 95 ram is multiport

TBI is still a good strong setup...
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Old June 9th, 2009, 11:30 PM   #6
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I have the same Suburban but a '94. They are only rated to tow 10k not 12k. I tow a 8000lb travel trailer...but not through the big hills/mountains of down south. I don't think my Suburban would handle the task. It tows my Jeep on a flat bed much easier than my TT.

And your truck is not carburated.....it's a TBI setup which GM started in '87 on their full size trucks.

Last edited by Roadhouse; June 9th, 2009 at 11:36 PM.
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Old June 9th, 2009, 11:42 PM   #7
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Many upgrades are available to give you a big increase in HP ant TQ with that motor a cold air intake is not one of them. The rest will cost a lot of money, heads, cam, computer, exhaust, holly TBI, ect ect ect $$$$$$$$

PS: If your motor was over heating that will kill your HP though because the computer will read it is running hot and retard timing. Flushing the radiator will not help if any of the tubes are clogged up it will only clean the tubes that flow. A new radiator might be a good start. Also do you have a transmission cooler? Towing up hills will over heat your tranny that is cooled by the radiator, if you have extremely hot tranny fluid running through the radiator it might not have the capability to keep both the motor and tranny cool, an external transmission cooler would be a huge upgrade for under $200.

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Old June 10th, 2009, 12:21 PM   #8
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Default 95 Suburban 2500, 7.4

Lots of good advice. The truck only has 78k miles, has a tranny cooler / tow package, flow master exhaust, and though I'm not sure what a TBI is, it does seem to have a 2 bbl carb with overhead electronic fuel injectors into the throat.

I guess the best is a diesel then. we plan to do the cross country thing and i know there are big hills / mountains out west too. It's a great truck, but I don't want to kill it or get stuck.

Thanks lots for the feedback.
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Old June 10th, 2009, 12:23 PM   #9
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anyone want to buy a 95 suburban w/ only 78,000 miles??? not enough muscle for the kind of pulling i need.
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Old June 10th, 2009, 04:08 PM   #10
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I had a 3/4 ton 95 - whatcha want for it? Got any pictures? I miss mine.
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Old June 10th, 2009, 04:18 PM   #11
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I had a 3/4 ton 95 - whatcha want for it? Got any pictures? I miss mine.
Just so you know, the dood appears to live in Jersey. Just a FYI...
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Old June 10th, 2009, 05:05 PM   #12
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Originally Posted by rriggs55 View Post
Lots of good advice. The truck only has 78k miles, has a tranny cooler / tow package, flow master exhaust, and though I'm not sure what a TBI is, it does seem to have a 2 bbl carb with overhead electronic fuel injectors into the throat.

I guess the best is a diesel then. we plan to do the cross country thing and i know there are big hills / mountains out west too. It's a great truck, but I don't want to kill it or get stuck.

Thanks lots for the feedback.
TBI stands for Throttle Body Injection, and you just described what a throttle body is, basically a carb body with two electric injectors at the top.

It shouldn't be, but it sounds like your motor is just worn out, like it overheated and needs a rebuild. I'd upgrade your injection system, and transmission.....

unless you have cash to burn on a diesel.
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Old June 10th, 2009, 07:16 PM   #13
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thanks greygoose, but I don't mind. I have driven farther for more stupid things. I might be proud of that?
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Old June 11th, 2009, 08:12 AM   #14
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thanks greygoose, but I don't mind. I have driven farther for more stupid things. I might be proud of that?
Well, are you?
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Old June 11th, 2009, 02:58 PM   #15
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shouldn't be worn out with the low miles, and the overheating returned to normal when the load of pulling the grade was gone. it's been maintained and i use synthetic hi temp oil, and only 2 - 3,000 miles on the rebuilt tranny from last June. And it's got enough muscle to smoke the tires - when I pulled into busy traffic once. It's a really good truck and I'd love to keep it, but plan to do more mountain driving and I don't want to beat up a good truck unnecessarily.

and this dood does live in Jersey, Princeton..

attached is one photo without much detail. No rust, tow package, carpet is dirty, but bought new carpet, just haven't had the time to replace. Would ask $7,500. Have more photos, just not on this pc.
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Old June 11th, 2009, 02:59 PM   #16
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Wonder if it would be worth to swap the engine and tranny for a Cummins w/ an Allison tranny...
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Old June 12th, 2009, 12:57 AM   #17
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Wonder if it would be worth to swap the engine and tranny for a Cummins w/ an Allison tranny...
I am looking to do the same swap with my 1988 4x4. Allison tranny's are expensive and not really any better then what you have. I have been researching and the failure rate is about the same only it will cost a hell of a lot more to rebuild that Allison. I have a th400 and you have a 4L80E, your tranny is basically a TH400 like mine but with overdrive. Both are strong reliable transmissions.

Some of the benefits to keeping either the 4L80E or Th400 is we would not have to fab any kind of mounts, change driveshaft lengths, parts would be cheaper if we ever had to rebuild, more aftermarket High performance parts available.

From the research I have been doing you can bolt a Cummings 12v up to the TH400 so it will bolt to your tranny as well. I think we need an adapter plate though and with a 4L80E you will need a stand alone transmission computer.

I am looking to do this swap not for towing but because of the rising price of gas and still being able to drive my truck...if I do this swap I will be making my own bio diesel fuel to run it on. Bottom line is this would be a simple, feasible and not very expensive conversion...I am still doing homework on it though.

Here is some info on the 4l80e behind a Cummings 12v http://www.dieselplace.com/forum/showthread.php?t=35435

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Old June 12th, 2009, 10:22 AM   #18
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Thanks, I've been doing research also on Hydrogen fuel cell packages. I guess I should do some research on the engine swap. Cheaper than a new truck..
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Old June 12th, 2009, 05:37 PM   #19
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You could always go with a turbo 6.5, that would bolt right up to your trans and existing engine mounts without any modification. That 's what I would do if I had your truck....
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Old June 12th, 2009, 08:35 PM   #20
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You could always go with a turbo 6.5, that would bolt right up to your trans and existing engine mounts without any modification. That 's what I would do if I had your truck....
The 6.5's suck though...many people are installing Cummings in these older Chevy's without any real issues.
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