View Full Version : Where can I buy 3.42 gear for 10.5
I tow many miles and the perfect road speed that the truck pulls the best is 60 @2600. I want to pull at 70-75. With my 4.10 thats about 3200. I have 4.10 in my truck would like to go to 3.42. Cant find a gear manufacture that makes 3.42 for 10.5 rear. GM had 3.42 in the 10.5 that was in the Yukon. GM gear is discontinued. Where can I get a 3.42 gear for K2500 10.5 rear.
DmaxMaverick
09-18-2007, 18:28
Randy's Ring & Pinion, www.ringpinion.com, sells them, but was out of stock last I heard.
4.10 to 3.42 is a big jump for towing. You will likely lose all your low end, and kill what highway mileage you do have. If it is able to pull it. Much depends on how much weight and the type of trailer you tow. 3.42 is fine for a daily driver and a weekend boat hauler (small boat), but will be a dog with any significant weight or high profile. Throw in a small grade, and it's finished. 3.73 would probably be a better option. If your rig is happy at 2600 RPMs with the 4.10, it will not be happy at 2600 RPMs with a 3.42. There's a pretty good reason they weren't availble OEM for your rig.
My thought was if needed the trans could be down shifted into 3rd would be about the same as OD with 4.10 or the old days of the TH-400/3.42 and my old 454. Occasionally I tow about 10,000lb enclosed trailer can be up to 13,000lb. Mostly tow the open trailer at about 6500lb. My neighbor's bone stock 93 6.5td 2500 has 3.42s from factory and will out pull my truck with the 6500lb trailer any day of the week. Mileage is not much towing. Truck gets about 18-20 around town about 14-16 on HWY and 10-12 with open trailer 7-8 with enclosed.
More Power
09-18-2007, 22:13
A member back in the late 90's from Billings, MT owned a 6.5TD K2500 and operated a commercial horse business. He transported horses around the country, mostly in the west. His truck was equipped with 3.42's and was used to towed a 6-horse slant-load trailer. He loved the gearing.
Only those who might not apreciate 3.42s are those who tow heavy or those who have never driven a 3.42 equipped 6.5. The key to successful towing with 3.42s is the engine rpm at the speeds you tow. Got to tow above 1800, preferrably closer to 2000-rpm to get the power you need. This usually means 65-75 mph. The big travel trailers or fifth wheels require lots of power above 65. So, if you have a moderate sized trailer with lower wind drag, 3.42s would be fine. Plus you'll really love them when running empty.
Jim
Hi there,
I have a 96 Suburban with 3.42 gears, while I don't do regular towing when I do it is usually with a 16 foot flat bed trailer which is supposed to be a 3 1/2 ton trailer but usually gets way over loaded. The max speed limit is dictated by what the trailer tires will take, checking regularly to see if they are getting too warm and also our roads here in Scotland aren't usually as long and straight as you guys and gals have in North America.
The sub copes power wise without any problem but I would warn you that with an automatic transmission if you hit really looooong very steep hills and are up in the 10,000 to 13,000 pound load you will find yourself down to first gear with the danger of the engine/transmission reaching stall speed.
I had this recently with a trailer load of soil and the trailer + load was up in the 12-13000 pound area (not including weight of the Suburban) and with a 90 degree turn 3/4 of the way up the hill I was almost at stall speed and also engine temps were higher than I have ever had. It did make it but it was nearly at stall speed.
I find that having low ratio available with the 4x4 means that I have the option of choosing low ratio to get me out of such a situation.
Don't know if your truck is 4x4 but if it is 2wd be careful in planning for any BIG hills.
Regards
Jim
Biggar, Scotland
Still waiting for the house to sell so we can move to Alberta.
My truck is a 4x4. I have also built a new engine for the truck that I am hoping will be stronger than the 460,000 mile bone stock engine in the truck that does a good job anyway. I have Holset turbo, marine spec pump, Intercooler, Marine injectors, Ported heads, cooling upgrades, transmission upgrades to come etc with the new combo. I know this truck is not a duramax and will never be. I dont pay $1000 payment on it either. The truck is driven empty most of the time now and will tow maybe 10-15 times a year long distance. The old truck just sucks to drive with the 70mph speed limits loaded or empty. Thanks for the reply guys and still would like to hear from 3.42 guys. I know most of the strokes were 3.50 I hear.
A member back in the late 90's from Billings, MT owned a 6.5TD K2500 and operated a commercial horse business. He transported horses around the country, mostly in the west. His truck was equipped with 3.42's and was used to towed a 6-horse slant-load trailer. He loved the gearing.
Only those who might not apreciate 3.42s are those who tow heavy or those who have never driven a 3.42 equipped 6.5. The key to successful towing with 3.42s is the engine rpm at the speeds you tow. Got to tow above 1800, preferrably closer to 2000-rpm to get the power you need. This usually means 65-75 mph. The big travel trailers or fifth wheels require lots of power above 65. So, if you have a moderate sized trailer with lower wind drag, 3.42s would be fine. Plus you'll really love them when running empty.
Jim
I tow an enclosed and open car trailer. I would like to tow at 70-75 mostly all Hiway now with 4.10s thats about 3100-3200 if my tach is right. The 3.73 might be about 2700. The 3.42 should be about 2300-2400. This truck pulls har from 2000-2600 and gets better mileage in that range. Dont care how heavy the load is it will drop to 2400- 2600 and just pull its ass off. Jelico/Mont eagle have been the only real big hills that I pull. Enclosed is 26ft. This truck out pulls any gas job I have had. Even seems to pull at least as good as the 454/3.42 truck that I had maybe better.
Well guys as my truck gets closer to the total transformation I am zeroing in on the details. After using the gear/mph calculator to decide what gear things just do not add up. Truck is supposed to have 4.10 gear. My truck has 265/75R16 tires at 50 mph I am turning 2000rpm in OD and in direct(3) about 2650. I think this truck has a 4.56 gear. Can someone check my math to see what they come up with. I might pull the rearend cover today to check it out.
Here is a screen dump of an RPM/Gear/Tire xls i wrote years ago.
DmaxMaverick
09-19-2007, 09:58
....I know most of the strokes were 3.50 I hear.
Most of them were/are 4.11. Ford required it for the higher GVWR/GCWR. Higher gearing could be had, but weight ratings were sacrificed. Many/most Dodge Cummins were 3.55. At the same time, it's like comparing apples to oranges. All the engines of the same era had different operating characteristics.
If your GCW is 21K+ 10 times a year for long distance, I think you really need to reconsider your 3.42 thoughts. That's a lot, both weight and frequency, and considerably over the truck's ratings. There's a lot more to practical (safe) towing than just what's under the hood. Higher gearing will also cause a significant hit to compression braking.
Quickv6:
Where are you located? I have a 3.42:1 axle I want to get rid of. It's out of a '93 pickup and has the G80 locking carrier. 50K miles towing a 2 horse trailer.
Most of them were/are 4.11. Ford required it for the higher GVWR/GCWR. Higher gearing could be had, but weight ratings were sacrificed. Many/most Dodge Cummins were 3.55. At the same time, it's like comparing apples to oranges. All the engines of the same era had different operating characteristics.
If your GCW is 21K+ 10 times a year for long distance, I think you really need to reconsider your 3.42 thoughts. That's a lot, both weight and frequency, and considerably over the truck's ratings. There's a lot more to practical (safe) towing than just what's under the hood. Higher gearing will also cause a significant hit to compression braking.
21K was the most I have ever towed and that was by accident. I picked up 32 box trailer from florida before the hurricane down there. My son was stuck and they put all of thier belongings on this trailer. I had no idea how heavy it was. Everyone thought cant be that heavy just furniture. I was moving him to IL. His 1/2 ton would not pull so I drove down to get it. When I hooked to it I knew it was heavy. After 1400 miles I decided to swing in a truck stop to check the weight. Man was I surprised 21,300lb truck and trailer. I tow mostly about 6500lb. The enclosed can get to 10K but only a couple times per year and only travel 250 mile hop to race. 3.42 might be too much of gear change.
Quickv6:
Where are you located? I have a 3.42:1 axle I want to get rid of. It's out of a '93 pickup and has the G80 locking carrier. 50K miles towing a 2 horse trailer.
Cincinnati OH I puled cover off it has a 4.10. The Tach is off 400 rpm comp-ared to the scanner. Scanner has 1725@50mph.
The Tach is off 400 rpm comp-ared to the scanner. Scanner has 1725@50mph.
Someone changed the alternator and put the wrong pulley on it...
If you ever get to eastern NY, I'll give you a good deal on the axle! ;)
What about deal on ring and pinion? Maybe I can drive to eastern NY.
Someone changed the alternator and put the wrong pulley on it...
;)
The alternator is where tach reads. Hummmm anyone know the size of the correct pulley?
More Power
09-19-2007, 21:48
62mm is what GM supposedly used on the 6.5 alternator, but this sometimes doesn't make it quite right (closer but..). You can get them in increments up to 67 the last I knew. A lot of the gas alternators come with a 55, which explains the high reading tachometers seen on the 6.5. A rebuilt found at most auto parts stores will likely have been a gas alternator - just more of them out there....
If you know what diameter the pulley is that you have now, and how far off the tach is, a little algebra could help you choose the right pulley. :)
Jim
A simple belt change on the Olds resulted in a 300RPM difference at 2000RPMs. 300RPMs less due to the thicker belt which road slightly higher on the pully.
DmaxMaverick
09-20-2007, 09:12
A simple belt change on the Olds resulted in a 300RPM difference at 2000RPMs. 300RPMs less due to the thicker belt which road slightly higher on the pully.
Not saying it didn't happen, but that doesn't make sense. The main pulley to alternator pulley relation is linear, and if the alternator pulley was riding higher, the main was as well (or should have been). I'd suspect something else in the works under that condition. 300 RPMs is a lot, and even if the differential was the thickness of a belt, you'd be hardpressed to get the math to work out. That's a 15% reduction, and I don't see it possible, even if the belt thickness could cause this effect.
Not saying it didn't happen, but that doesn't make sense. The main pulley to alternator pulley relation is linear, and if the alternator pulley was riding higher, the main was as well (or should have been). I'd suspect something else in the works under that condition. 300 RPMs is a lot, and even if the differential was the thickness of a belt, you'd be hardpressed to get the math to work out. That's a 15% reduction, and I don't see it possible, even if the belt thickness could cause this effect.
Your assuming that the inside width of both pullies are identical. This is not true. I believe the belt on the crank pulley was riding on the bottom inside of the belt and still "mostly" is on the new belt. On the alternator it is riding on the sides only just off the bottom.
Like you I was suspicous, and actually put the old belt back on, then looked around for what was different.
DmaxMaverick
09-20-2007, 10:01
Your assuming that the inside width of both pullies are identical. This is not true. I believe the belt on the crank pulley was riding on the bottom inside of the belt and still "mostly" is on the new belt. On the alternator it is riding on the sides only just off the bottom.
Like you I was suspicous, and actually put the old belt back on, then looked around for what was different.
I'm not assuming anything. Just saying it doesn't make sense. It will take a lot more than the thickness/width of a belt to get a 15% difference. How the belt rides on the pulley may make a difference, but I doubt it would be noticeable. Probably in the 1-2% range. If the inside and outside of the belt were riding on different parts of the pulley, one or the other or both has to slip, whichever has the least friction. I'm not calling foul on your theory, just saying I think there's more to that problem than just the belt size.
I'm not assuming anything. Just saying it doesn't make sense. It will take a lot more than the thickness/width of a belt to get a 15% difference. How the belt rides on the pulley may make a difference, but I doubt it would be noticeable. Probably in the 1-2% range. If the inside and outside of the belt were riding on different parts of the pulley, one or the other or both has to slip, whichever has the least friction. I'm not calling foul on your theory, just saying I think there's more to that problem than just the belt size.
mmmmmmm, well I unfortinuatly have already tossed the old belt, it was severely worn. Like I said, I swapped the old bect back on, got my 300rpms back! I guess we're left to speculation at this point.
If you can think of anything else I'm willing to test it!
Shikaroka
09-21-2007, 11:29
st is 60 @2600. I want to pull at 70-75. With my 4.10 thats about 3200.
I thought that sounded aweful high.
I had 4.10s in my burb and could easily get her up to 90mph, and still be beneath the red-line.
I now have 3.73s in there. I think they are a good comprimise, but I don't tow that much and you have more mods then me.
My 3.73 puts me at 2250 rpm at 70mph. I find this the best compromise between speed and efficiency. Above 70-73 drag really starts taking its toll on mileage.
In town driving say 55mph stop and go I can get as high as 20 18 is a good avg. On the highway 70 with cruise 14-15. Knowing the tach is off corrected I would be at 2600-2700.
I would like to pull the car trailer 70-75. With 3.42 I would be at 75@2000 in OD and 3rd gear 2500 if downshift is needed. My truck pulls like a raped ape 1800-2400. I think it will work. New combo should have more power to help things out. The neighbor's 93 with 3.42 will kick the pants off my truck towing on the highway.
DA BIG ONE
09-22-2007, 04:38
I've had 3.42's for sometime now, great on highway but w/auto at lower speeds it can be PITA and use much more fuel than w/4.10's around town.
I have an AutoTrac (3 speed sensors) so more issues than other t-cases, if vssb is hacked to correct speedo then shifts points will spread & od/lockup is @60+mph, hack signal to vssb then shifts will go back to where they were w/4.10's but trans pressure needs to be brought down to prevent banging of gears.
I have every mod except 4" exhaust & the burb is an animal that performs beyond expected w.3.42's & 33" tires, w/4.10's and stock tires always light up tires "not good"
6.5 Detroit Diesel
09-22-2007, 09:29
I know that with the FF the rear end ring gear is 10.5. What is the diameter of the front ring gear?
I've had 3.42's for sometime now, great on highway but w/auto at lower speeds it can be PITA and use much more fuel than w/4.10's around town.
Thats the crazy thing about my truck with 4.10s it will get 18 and close to 20 at times around town. On the highway you need a tanker to drive it. I have never owned anycar or truck that was not the opposite. I am also looking at the 3.73 but I think the 3.42s is what I am going to try. I can always go to 3.73s if it doesn't work out
What about deal on ring and pinion? Maybe I can drive to eastern NY.
I don't want to separate it. Buy the whole thing, get the locker and it's all set up...
I don't want to separate it. Buy the whole thing, get the locker and it's all set up...
Drop me an email with price info@extremeautomatics.com
moondoggie
09-26-2007, 07:05
Good Day!
If your VSSB hasn't been calibrated for your 265/75R16 tires, your going ~ 4% faster than your speedo says - factory stock 245/75R16s are ~ 30.47" OD, 265/75R16s are 31.65" OD.
At actual 70 mph, with 4.10 gears (which virtually all 6.5s came with), & your tires:
in 3rd: ~ 3050 rpm
in OD: ~ 2290 rpm
"I want to pull at 70-75. With my 4.10 thats about 3200." Sounds like you were pulling in 3rd, or your tach is off. From years of reading here on the Page, there's absolutely no reason to not pull in OD. Mind you, don't call me if you do & your tranny blows up, but I base this on lots of reading. I would hope our experts might point out where / if this is in error.
At actual 70 mph, with 3.42 gears & your tires:
in 3rd: ~ 2540 rpm
in OD: ~ 1910 rpm
Seems like going to 3.42s would make OD pretty much useless for towing; you might see a little better mpg when driving empty. I made multiple changes to my 95 pickup (including a Gear Vendors Aux. OD) & went from effective overall ratio of ~ 3.80 to ~ 3.08; my annual mpg climbed I think 2 mpg; keep this in mind when considering what to do.
ronniejoe has made the same observation you have about the 6.5's useful power band: taller gears WITH A STOCK MOTOR seem to work better. He surmises it's because the stock turbo lays down at > 2600 rpm, which is why he's attempted to pursue a turbo that's better matched to the 6.5, allowing MUCH better power all the way to the governor.
Good luck with your decision; keep us posted, OK?
Blessings!
Good Day!
If your VSSB hasn't been calibrated for your 265/75R16 tires, your going ~ 4% faster than your speedo says - factory stock 245/75R16s are ~ 30.47" OD, 265/75R16s are 31.65" OD.
At actual 70 mph, with 4.10 gears (which virtually all 6.5s came with), & your tires:
in 3rd: ~ 3050 rpm
in OD: ~ 2290 rpm
"I want to pull at 70-75. With my 4.10 thats about 3200." Sounds like you were pulling in 3rd, or your tach is off. From years of reading here on the
The tach is off about 400 RPM. 4L80E will handle towing in OD thats what I do to pay the bills. (Transmission/performance shop) I am reconsidering going to the 3.73. Although 3rd with 3.42s seems like an option for a steep hill. I dont know how the new engine is going to pull compared to the old 467,000 engine. But now I know that my tach is off 400. I now know my truck pulls best between 1800-2200. With the 4.10s in OD it will drop to 60mph and just sit there and dig does not seem to matter about the weight behind the truck. My thought is with the 3.42 maybe I could move this sweet spot to 75 MPH. Most are saying here that this will not happen. They say 3.42s will kill my highway power. Has anyone made the switch to 3.42 on a truck that tows? Or How has the 3.73 worked out when going from 4.10s. Did you lose highway road speed pulling when you went to 3.73?
Just a small item to consider ( probably in the post somewhere )
You can't control TCC lock up speed, the higher the gear ratio ( also bigger tires )the higher the TCC lock up speed, with 3.42 the TCC lock up would be about 55 MPH (approx )
That is for 3rd and OD ) , also TCC lock up is based on Engine load.
you may never get TCC locked. That is if you don't have a Sw to force TCC lock up.
DA BIG ONE
09-27-2007, 13:47
Just a small item to consider ( probably in the post somewhere )
You can't control TCC lock up speed, the higher the gear ratio ( also bigger tires )the higher the TCC lock up speed, with 3.42 the TCC lock up would be about 55 MPH (approx )
That is for 3rd and OD ) , also TCC lock up is based on Engine load.
you may never get TCC locked. That is if you don't have a Sw to force TCC lock up.
w/3.42's + 33.0" tires you are looking at 60mph lockup.............if it locks at all.................
moondoggie
10-01-2007, 09:45
Good Day!
"The tach is off about 400 RPM." "But now I know that my tach is off 400." So, your belief is that you're turning ~ 2800 rpm @ 70 mph (I will assume you didn't mean 3600, which is unlikely as these things are I think governed to 3500). Please, no offense intended, just seeking knowledge, but why does this not agree with the math? I've always found these calculated rpm to agree with reality to a startling degree; your data suggests a HUGE error of some sort.
Thanks & good luck with whatever you decide to do.
Blessings!
(signature in previous post)
Good Day!
"The tach is off about 400 RPM." "But now I know that my tach is off 400." So, your belief is that you're turning ~ 2800 rpm @ 70 mph (I will assume you didn't mean 3600, which is unlikely as these things are I think governed to 3500). Please, no offense intended, just seeking knowledge, but why does this not agree with the math? I've always found these calculated rpm to agree with reality to a startling degree; your data suggests a HUGE error of some sort.
[/I][/CENTER]
In the process of gear hunting I discovered that my tach was reading 400-500 high. at 75 mph I thought I was at 3000 rpm I was really at 2500-2600 70mph about 2300-2400. This has been verified with a scan tool. My truck pulls best 1800 - 2400 some where in there but 1900-2000 seems to be the real sweet spot. I was looking for a gear ratio to pull at highway speeds of 70-80 mph and be in the 2000 rpm range. and try to hold road speed to an average of say 70mph being able to downshift into 3rd if needed.
3.42 @75 in 4th-2050 rpm 70mph downshift 3rd-2550 rpm
3.73@75 4th-2200 70 mph downshift 3rd-2800
So finding that downshift road speed for both gears is well above the sweet spot the approximate pulling speed would be in 3rd 4.10@53 mph 3.73@57 3.42@61
After looking closer the 3.73 in 4th is about 68 mph and is a little above the sweet spot of 1800-2000 in 4th gear with no downshift needed. Probably the best choice.
The 3.42 is about 1900 right in the middle. I am thinking maybe a good choice as new engine will have more power.
The known is I have had 4.10s for 460,000+ miles and it is too much gear for my trucks use.
I sold Western Star and Mack trucks for years. In the process of setting up a chassis we geared fast and run slow for best fuel economy looking at the road speed the truck was intended to run and the specific RPM range of the engine. I know I am over thinking this but if this were a large truck the 3.42s would be what I would spec based on the performance of my truck over the last 466,000 miles.
I would love to hear some comments on this theory. good or bad Help me to see the light.
DA BIG ONE
10-01-2007, 15:30
In the process of gear hunting I discovered that my tach was reading 400-500 high. at 75 mph I thought I was at 3000 rpm I was really at 2500-2600 70mph about 2300-2400. This has been verified with a scan tool. My truck pulls best 1800 - 2400 some where in there but 1900-2000 seems to be the real sweet spot. I was looking for a gear ratio to pull at highway speeds of 70-80 mph and be in the 2000 rpm range. and try to hold road speed to an average of say 70mph being able to downshift into 3rd if needed.
3.42 @75 in 4th-2050 rpm 70mph downshift 3rd-2550 rpm
3.73@75 4th-2200 70 mph downshift 3rd-2800
So finding that downshift road speed for both gears is well above the sweet spot the approximate pulling speed would be in 3rd 4.10@53 mph 3.73@57 3.42@61
After looking closer the 3.73 in 4th is about 68 mph and is a little above the sweet spot of 1800-2000 in 4th gear with no downshift needed. Probably the best choice.
The 3.42 is about 1900 right in the middle. I am thinking maybe a good choice as new engine will have more power.
The known is I have had 4.10s for 460,000+ miles and it is too much gear for my trucks use.
I sold Western Star and Mack trucks for years. In the process of setting up a chassis we geared fast and run slow for best fuel economy looking at the road speed the truck was intended to run and the specific RPM range of the engine. I know I am over thinking this but if this were a large truck the 3.42s would be what I would spec based on the performance of my truck over the last 466,000 miles.
I would love to hear some comments on this theory. good or bad Help me to see the light.
I've been running 3.42's & 33" tires for some time now passing in 3rd gear between 70 & 80 mph is a thrill when it hits 4th you think your are in a performance big block car, however short lived..............................now if I can only get to 5,000 rmps!
moondoggie
10-01-2007, 17:53
Good Day!
Thanks. Let us know how it comes out. :D
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