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I have an '07 LBZ crew cab 2wd dually that I tow a 48' race car trailer with living quarters with, usually weighing in the 29,500 range total. I was putting brakes on it this past weekend and saw that the pinion had a little movement in it. Pulled the rear end apart and one of the bolts that holds the spanner locks in had backed out, and the bolt and spanner lock got thrown up into the pinion bearings and the front pinion bearing ended up tearing up the pinion, and wore it down. So there's no interference fit at all. It'll flop around on there. So I need to buy a ring and pinion.


I run Michelin 235/85-16 LTX M/S2 tires which are a little bigger than stock at 31.7", stock being roughly 30.3". I travel all over the place doing 75mph plus or minus a little most of the time.


Can anyone speak from experience on switching to a 4.10 gear in a similar situation? A 4.10 would put me at ~1920rpm at 72mph, where as 3.73s and stock tires would have been ~1830. My fuel mileage ranges around high sevens to low and mid eights most of the time. Most of the routes I travel are hilly, and thinking the gears may help keep it in it's happy power range better. If I'm running 80, it'll definitely hold speed better on hills than it will at 70 with the RPM being higher. Seems to me like a 4.10 would be the right move.


I do run a PPE handheld on economy mode. EGR delete, Pro Fab Y bridge, down pipe, 5" straight exhaust, ARP head studs, etc.
 

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4.10 for DDing more than towing
4.56 for towing more than dding

Ideally 4.30 would be great but finding 4.30 for the front is almost impossible

I run 4.56 with a 32" tire [email protected] In 6th
Also recommend a low stall TC. Take advantage of the extra gear multiplication without blowing through the TC in stop n go traffic and starting on hills..,
I run a transtar AX7L ~1700stall for last ~120k miles at ~400rwhp grossing upwards of 36,000lbs. I would also suggest jr kit a s main line pump pressure mod while trans is out.
A7XL was 250+100 core when I did mine last year.. I doubt it would hold max effort stock fuel dmax but that's not what I was after
 

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Drive the truck in 5th and see if you like those rpms. Thats almost exactly were 4.30's would put you in 6th.

I have 4.44 and love them but I rarely run over 70mph.
At your weight and speed I think 4.10/4.30 would be great.


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I have a 2WD dually also and want to switch the rear gear out for 4.10s. Truck just seems to work to hard with the bigger loads. Empty it is great with the 3.73 gear. I also have larger than stock tires.
 

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Discussion Starter #6
Wanted to bump this up and see if anyone else had any input. I am still running 3.73s for now
 

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Seems like the Cab and Chassis trucks use the 4:10 gears-- as they are usually heavier and only driven on short trips. You should be fine with the 4:10, as you already changed the final gear ratio higher by adding larger tires. The Allison would like it also.
 

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Discussion Starter #8
Bump. Still thinking it would be the right move but would like to hear from guys who run 4.10s and do a lot of highway driving.
 

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Any new or additional opinions? The truck has 440k on it now, the rear end is getting significantly more whine. It's going to be time soon. I think 4.10 is the way to go.
 

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I don’t know the best option for you, but how about a photo of the race car!!
 

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Any new or additional opinions? The truck has 440k on it now, the rear end is getting significantly more whine. It's going to be time soon. I think 4.10 is the way to go.
Malibu and Kow covered it some time back.
But,
Stock tires and 3.73 @ 1830...you're running in 6th.

Better performance would be 2050 in 5th, pushing to 2200 on climbs....with stock size tires.
 

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Any new or additional opinions? The truck has 440k on it now, the rear end is getting significantly more whine. It's going to be time soon. I think 4.10 is the way to go.
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You are pulling 30,000 lbs with a older 3500 with 440,000 miles on it, and going 80 mph?

Hopefully, you don't do that near me - sounds like a combination of total irresponsibility towards your fellow highway users, combined with a lack of understanding of the capacity info. of your series of truck.

Hopefully, you will come to your senses and buy a larger, heavier truck whose towing capacity meets your requirements.

As a side note, assuming your existing truck has an Allison automatic transmission, depending on the year and model it will have at least 5 forward speeds in high gear. Yes, when running at, near, or above rated towing loads, you will see slowing on grades. Again, if you cannot deal with the laws of physics causing your existing truck to slow down when pulling that kind of load up long up-grades, sounds to me like you should consider a larger, heavier tow vehicle matched to the weight you want to pull.
 

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Malibu and Kow covered it some time back.
But,
Stock tires and 3.73 @ 1830...you're running in 6th.

Better performance would be 2050 in 5th, pushing to 2200 on climbs....with stock size tires.
Hook, is that for the 30k weight? If I'm running with a 40' gooseneck with 15-20k does that still apply. 'Course I'll be somewhere around 55-65mph. Thanks
 

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You are pulling 30,000 lbs with a older 3500 with 440,000 miles on it, and going 80 mph?

Hopefully, you don't do that near me - sounds like a combination of total irresponsibility towards your fellow highway users, combined with a lack of understanding of the capacity info. of your series of truck.

Hopefully, you will come to your senses and buy a larger, heavier truck whose towing capacity meets your requirements.

As a side note, assuming your existing truck has an Allison automatic transmission, depending on the year and model it will have at least 5 forward speeds in high gear. Yes, when running at, near, or above rated towing loads, you will see slowing on grades. Again, if you cannot deal with the laws of physics causing your existing truck to slow down when pulling that kind of load up long up-grades, sounds to me like you should consider a larger, heavier tow vehicle matched to the weight you want to pull.
pulled 30k trailer all day long.. some one is late to the game... or weight police....'dunno;
Hook, is that for the 30k weight? If I'm running with a 40' gooseneck with 15-20k does that still apply. 'Course I'll be somewhere around 55-65mph. Thanks
my question would be how often are you towing said weight?
bigger tires?
25/75? loaded/empty
50/50?
75/25?
a lot of rolling hills where you usually travel?

if its couple times are year I wouldn't spend the ~1500.00 to re-gear both axles.. if daily/weekly yeah I would definitely look at re-gearing.. 5sp with stock tires ~31" and 3.73 ran [email protected] with 6sp, 4.56:1 and 32" tires was [email protected]

yes it will do it with 3.73.. dropping to 4.1/4.56 just take some strain of the trans and definitely helps startibility and backing making it all easier

going to lower gear allows for the TCC to lock up sooner. with 3.73 you're mid 20mph with 4.56 I was locking the TCC around 11-12mph, 4.10 should be ~15mph, made a huge difference in driveability in stop n go traffic, especially coupled with a low stall TC..
I avg 80-90* over ambient with the trans temp after gear swap and low stall TC, with stock transcooler

sorry I don't have a definitive answer you kazman
 

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Thanks Malibu. All stock here. We are just getting things lined up to start a little travelling program to introduce younger kids and parents to motorcycling. Submitted a design to inTech trailers for a 40' wedge goosneck with living quarters. I'm guessing that we'll be pulling that package 6-8 weekends this year if we get the trailer early enough. Fairly flat here in California, but if we start going to neighboring States or across country with this it will be more.

Since I'm new to the diesel stuff, was just curious about Hook'ems comment about using 5th gear. I've pulled our 20'er several times and haven't had any issues and have tried it with tow setting on and off. Prefer the Towing on as it just seems the engine/tranny seem happier, but am a rookie so asking the basic questions as well.
 

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Thanks Malibu. All stock here. We are just getting things lined up to start a little travelling program to introduce younger kids and parents to motorcycling. Submitted a design to inTech trailers for a 40' wedge goosneck with living quarters. I'm guessing that we'll be pulling that package 6-8 weekends this year if we get the trailer early enough. Fairly flat here in California, but if we start going to neighboring States or across country with this it will be more.

Since I'm new to the diesel stuff, was just curious about Hook'ems comment about using 5th gear. I've pulled our 20'er several times and haven't had any issues and have tried it with tow setting on and off. Prefer the Towing on as it just seems the engine/tranny seem happier, but am a rookie so asking the basic questions as well.
Kaz, sounds like a fun adventure and I wish you luck.

You will need to keep in the back of your mind some weight issues due to your living in CA. While I have never driven a truck out there, I have heard lots of horror stories about CHP, DOT and others pulling folks over and doing spot weighs on their rigs.

The reason that I am passing this along is that if you end up with a 40' goose with living quarters and loaded, you will most likely find that your trailer weight exceeds 10K which will put you into CDL territory if you are operating the rig in a commercial venture. However, if you register it as private or an RV, you should have no issues. Just something to consider.

Back on topic.......
 

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Thanks JimmyD. Hoping it will be fun as it won't be a true money maker in the beginning. Breaking even would be fantastic. And yes, I've been doing all my research and trying to establish staying under weight and under max combined length which is why 40' and not 42', 44', ??. Current strategy is to be private/RV, however, there's one brain cell that says just get a Class A non-commercial and be done with it, or just get a commercial and in the future I could perhaps explore new job potentials driving a rig for one of the race teams :)

okay...back on topic!
 

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If I'm running with a 40' gooseneck with 15-20k does that still apply.
If I hook on to a trailer, regardless of what it is or if it's loaded or unloaded, the T/H button gets pushed. There's no reason not to, you're not saving anything.
Unlike on a car, On or off, it's different from a car transmission's selecting Tow and what it does on the Allison

As to 5th, or any gear you lock out too, with what ever you're pulling or the grade, the selective shift allows you to control what RPMs you're running, @ what speed.

Most reasonable folks are going to hwy tow their trailer in the 65-72mph zone. And the HD will try and pull that all day in 6th gear at the lowest RPMs, which can be below 1700.

However, if you lock out 5th, that brings your Rs up to 1900-2100, which is the sweet spot for the Dmax. You'll run cooler, lower EGTs, use less fuel and climb the hills easier. And of course if the hill worsens, drop down to 4th and stay up in that higher RPM.
 

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Got it! Just needed to verify you were talking about the sweet spot and the what range rpm's they are.! I did eventually start playing with the gear select switch as I was chasing mpg and watching the instant mpg gauge. Same principals as racing and finding the correct gearing to utilize the engine. Thank you Sir!
 

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pulled 30k trailer all day long.. some one is late to the game... or weight police....'dunno;...…...my question would be how often are you towing said weight? …………...a lot of rolling hills where you usually travel?...…. kazman
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Yes - I know a lot of folks like you - we have some posting in here; they are satisfied their knowledge of engineering and metallurgy is superior to the factory folks who design & engineer our trucks.

No, I am not personally in law enforcement, so the term "weight police" does not apply to me personally. More and more states are equipping their law enforcement to enforce weight limitiations - glad of that; the more they get over-loaded trucks impounded and off the road, the safer my family and I are. As for your other comments - no, I am not exactly "late to the game"...I started driving multi-axle heavy vehcles in 1956. And no, I do not try and tow 30,000 lb. or so weights with my own truck - if I had to tow a load like that, I'd buy a truck "rated" for that kind of load.

So the "bottom line" answer to the initial question is - "no, I have not re-geared my truck from the stock 3.7 final drive". The "higher" (as in lower numerically) the final drive ratio, the lower the engine rpm. Modern transmissions, in particular the Allisons behind our Duramax's, are quality well-designed units. Operated within their design limitations, I cant imagine anyone who respects the laws of physics and safety concepts wanting to change.
 
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