I thought I would post my latest updates to our Suburban. Had some nice weather yesterday and got some work done.
In my last post, I had regeared from 3.73's to 4.56's. My truck and trailer specs are in that post.
3.73->4.56 Regear Results
I am still super pleased with the change, even in daily driving. Towing was vastly improved. Towing fuel mileage also improved.
However one thing we ran into on our test trip was cooling on big grades...we pulled a few hills (11% grade when I looked them up later) that still required 2nd gear, and the temperature would start creeping past 230, so I started looking for solutions.
Fan and Clutch
The later model trucks had a much improved 11 blade fan. I happen to get a super cheap parts truck that had this fan and a brand new severe duty clutch. So I swapped them out.
Here is my old "HD Cooling Package" 5 blade fan with hd clutch vs the new setup.
There is a huge difference in the air moved by the new setup. Should help the AC function at lower speeds as well.
Exhaust Mid-Pipes
The second change I wanted to make for a long time is the mid pipes. The Vortec 5.7 1500 trucks had tiny 1 7/8-2" pipes that were crush bent, so they were as small as 1 5/8 at the bends.
The 3500 trucks with the same 5.7 had huge 2 3/4 pipes even though they had the same power rating. Seems that this might help reduce heat under sustained high rpm high load pulls.
Jeg's sells a 2 1/4 mandrel bent set that bolts in. My cats are already deleted in the tune so no worries there.
I also took the opportunity to replace my 138K mile 23 year old o2 sensors.
I got stainless steel so hopefully they don't give me any rust issues.
Payload guys will be happy to hear this shaved at least 20lbs off the truck, so I can carry more snacks and beer. ๐
I still have the factory muffler and tailpipe so the sound output is only slightly louder. I do have a cat back exhaust for it but I don't want to be fighting drone while pulling the trailer.
The pipes cost $160 on sale, normally $230. The fan and clutch would have run me about $100 if I didn't have the parts truck. Less then a single payment on a base model new truck so I'm not to disappointed with that.
We have a few long trips planned this summer, so I will be sure to update with the results. First short trip is in 2 weeks, but its all flat roads. If I still have cooling issues on challenging grades I will move up to a 2 core radiator.
Love this old truck!
In my last post, I had regeared from 3.73's to 4.56's. My truck and trailer specs are in that post.
3.73->4.56 Regear Results
I am still super pleased with the change, even in daily driving. Towing was vastly improved. Towing fuel mileage also improved.
However one thing we ran into on our test trip was cooling on big grades...we pulled a few hills (11% grade when I looked them up later) that still required 2nd gear, and the temperature would start creeping past 230, so I started looking for solutions.
Fan and Clutch
The later model trucks had a much improved 11 blade fan. I happen to get a super cheap parts truck that had this fan and a brand new severe duty clutch. So I swapped them out.
Here is my old "HD Cooling Package" 5 blade fan with hd clutch vs the new setup.
There is a huge difference in the air moved by the new setup. Should help the AC function at lower speeds as well.
Exhaust Mid-Pipes
The second change I wanted to make for a long time is the mid pipes. The Vortec 5.7 1500 trucks had tiny 1 7/8-2" pipes that were crush bent, so they were as small as 1 5/8 at the bends.
The 3500 trucks with the same 5.7 had huge 2 3/4 pipes even though they had the same power rating. Seems that this might help reduce heat under sustained high rpm high load pulls.
Jeg's sells a 2 1/4 mandrel bent set that bolts in. My cats are already deleted in the tune so no worries there.
I also took the opportunity to replace my 138K mile 23 year old o2 sensors.
I got stainless steel so hopefully they don't give me any rust issues.
Payload guys will be happy to hear this shaved at least 20lbs off the truck, so I can carry more snacks and beer. ๐
I still have the factory muffler and tailpipe so the sound output is only slightly louder. I do have a cat back exhaust for it but I don't want to be fighting drone while pulling the trailer.
The pipes cost $160 on sale, normally $230. The fan and clutch would have run me about $100 if I didn't have the parts truck. Less then a single payment on a base model new truck so I'm not to disappointed with that.
We have a few long trips planned this summer, so I will be sure to update with the results. First short trip is in 2 weeks, but its all flat roads. If I still have cooling issues on challenging grades I will move up to a 2 core radiator.
Love this old truck!
Love that era too...albeit there were issues and solutions will touch oh below
Std Duty vs HD & Severe Duty fan clutches has the std duty couple water pump shaft RPMs to the fan around 50%-60%. Where as the HD & Severe duty couples +90T% of the water pump shaft RPMs to the fan blade.
Difference between the HD and Severe duty is with the shaft bearing. Since the Severe Duty pulls +25HP it wants to make like an airplane propeller...and if the bearing lets loose...it will punch a hole in the radiator
Hope you changed the serpentine belt too. Also the tensioner, they squeak just before they either freeze up or fall apart around 100K miles when towing heavy, because the clutch turns on more often
Surprised you managed to fit that fan blade/clutch into the fan shroud. Good going !!!
Mine ROARs when it kicks in and then can see the dash temp gauge needle drop like a rock. Mainly comes on when towing heavy.
From your pic...did you remove the CATS ? This era GM Small Block really likes to have the exhaust opened up....headers realy wakes most all 5.7L's
1996 was one of the first years the Big Three changed coolant to match foreign badges and their 100K mile guarantee. Placating dealerships (they don't like to flush coolant, messy job and low margin). So GM worked with Texaco to formulate DeathCool (look that up here and out in the open web)
Will post on the other DeathCool thread after this post
Good to hear of your good experience going to higher numeric diff ratio. Getting close to having to rebuild my 7.4L and while at it, going to 5.xx diff ratios and a Gear Vendor to change my 4 speed 4L80E into an 8 speed automatic
Consider changing to copper core spark plugs if you are willing to change them every 30K-40K miles. Platinum's are just okay, IMHO, and more for their 100K mile life than performance
And consider changing the intake filter from the standard duty to a HD air filter. Your 5.7L and my 7.4L filter box are the same. GM has a HD filter that is about 2" larger in dia (more filtration area and lower PSI drop). If photobucket images don't show, I'll come back later to fix
Pictures of the spark-plug mod and air filter at this link: Something is wrong with the beast!! page 3
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26732781/gotomsg/26733766.cfm#26733766
Click For Full-Size Image.
Std Duty vs HD & Severe Duty fan clutches has the std duty couple water pump shaft RPMs to the fan around 50%-60%. Where as the HD & Severe duty couples +90T% of the water pump shaft RPMs to the fan blade.
Difference between the HD and Severe duty is with the shaft bearing. Since the Severe Duty pulls +25HP it wants to make like an airplane propeller...and if the bearing lets loose...it will punch a hole in the radiator
Hope you changed the serpentine belt too. Also the tensioner, they squeak just before they either freeze up or fall apart around 100K miles when towing heavy, because the clutch turns on more often
Surprised you managed to fit that fan blade/clutch into the fan shroud. Good going !!!
Mine ROARs when it kicks in and then can see the dash temp gauge needle drop like a rock. Mainly comes on when towing heavy.
From your pic...did you remove the CATS ? This era GM Small Block really likes to have the exhaust opened up....headers realy wakes most all 5.7L's
1996 was one of the first years the Big Three changed coolant to match foreign badges and their 100K mile guarantee. Placating dealerships (they don't like to flush coolant, messy job and low margin). So GM worked with Texaco to formulate DeathCool (look that up here and out in the open web)
Will post on the other DeathCool thread after this post
Good to hear of your good experience going to higher numeric diff ratio. Getting close to having to rebuild my 7.4L and while at it, going to 5.xx diff ratios and a Gear Vendor to change my 4 speed 4L80E into an 8 speed automatic
Consider changing to copper core spark plugs if you are willing to change them every 30K-40K miles. Platinum's are just okay, IMHO, and more for their 100K mile life than performance
And consider changing the intake filter from the standard duty to a HD air filter. Your 5.7L and my 7.4L filter box are the same. GM has a HD filter that is about 2" larger in dia (more filtration area and lower PSI drop). If photobucket images don't show, I'll come back later to fix
Pictures of the spark-plug mod and air filter at this link: Something is wrong with the beast!! page 3
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26732781/gotomsg/26733766.cfm#26733766
Click For Full-Size Image.
