Jump to content

3.73 & Z71 Question... Again -- Sorry!

piscator

Recommended Posts

piscator Enthusiast

piscator

Posted
Posted

Sorry to ask about a 'well-worn' topic, but I don't want to start negotiations on a 2009 Sierra when I still don't understand 'rear differential gearing'! This Sierra I found is a 5.3, crew cab, with 3.73 rear end.

 

If I read the achive threads correctly, 3.43 is the standard ratio, while 3.73 & 4.10 are optional. I've also learned that:

 

Higher number = easier towing

Lower number = better gas mileage

 

Yes? No? And if so, WHY?? I really don't understand what the trade-offs are -- help!

 

I tow a 24' fishing boat on weekends and plan to take it up to Maine for vacation. Aside from that, my truck is a 'daily driver' that is used to haul my daughters' kayaks, bicycles, etc.

 

My Silverado 5.3 with 3.42 seems to do the job, but "what do I know?" :cheers:

 

The 'sticker' on the Sierra I found reads:

 

SIERRA 1500 4WD EXT CAB SLT

VORTEC 5.3L V8 SFI ENGINE W/ACTIVE FUEL MANAGEMENT

4-SPEED AUTOMATIC TRANSMISSION

 

7,000 LBS GVWR

3.73 REAR AXLE RATIO

 

HEAVY DUTY TRAILERING EQUIPMENT

LOCKING REAR DIFFERENTIAL

AUTOTRAC TRANSFER CASE.

 

So is all of this good? Is it 'way better' than my 2000 Silvy with 3.42?

 

The 09 Sierra under discussion has the Z85 suspension package. My Silvy has the Z71. Did I read correctly that the only difference between Z71 and Z85 is shocks, skid plates, and 'high output' decals? :D

 

Am I correct that I can uprgrade the 09 Sierra to Z71? If it's 'just shocks', should I let the dealer do this now, or wait a while?

 

I really appreciate everyone's help. You've gotten me this far! I'll probably start negotiating on the 09 Sierra next week!

 

Thanks! piscator

BuckFeverZ Senior Enthusiast

BuckFeverZ

Posted
Posted

IMO 3.73's is the best compromise if your just towing occasionally. You still have some down low power to get the load moving, but you still have better MPG's than if you had 4.10's.

J-man67 Senior Enthusiast

J-man67

Posted
Posted
IMO 3.73's is the best compromise if your just towing occasionally. You still have some down low power to get the load moving, but you still have better MPG's than if you had 4.10's.

 

Agreed!

Ryan00TJ Enthusiast

Ryan00TJ

Posted
Posted

X3, I like my 3.73 gears along with the 5.3L. I tow a 5Klbs boat in the summer and it seems to work very well.

 

 

4.10's = lower gearing than say 3.42's despite the number being higher. The lower the gearing the more torque and rpms. The faster your engine will rev and get in the powerband. Tradeoffs are less MPG and more engine rpms.

 

3.42's = higher gearing than say 4.10's despite the number being lower. Generally the higher the gearing the truck will achieve better MPG but rev slower and stay low in the powerband.

 

The options on the 09 are nice. Same as mine. Test drive the truck. I beleive you will find its a better powertrain with 315hp and 3.73 gearing vs your 5.3 and 3.42's.

 

If the 09 is not a Z71 from the factory and not a Z60 its a Z85. I've never heard of a dealer doing a Z71 upconvert but its possible I guess. '

 

Good luck on the new truck.

MarkD Senior Enthusiast

MarkD

Posted
Posted

I would stick with the 3.73's, especially if you are happy with the 3.42's.

 

If you could find a truck w/ a 6-speed, I think their 1st gear is lower and offers the best of both worlds.

 

 

Maybe this will help...

 

What the gear ratio means is that what ever number is posted as the gear ratio is the number of turns of the driveshaft for every one turn of the rear axle.

 

The higher the number, the more turns of the driveshaft per turn of the rear axle. The more turns of the driveshaft per turn of the rear axle, the easier it is for the driveshaft to turn.

 

If you ever rode a 10-speed bike in first gear you peddle like crazy, it is real easy to peddle but you don't go very far for all that work. The more steps you take up in gearing, the harder it is to peddle, but you go further with each gear for the same amount of peddle revolutions.

 

First gear is like 10:1 real easy, 10th gear is like 1:1 really hard if you aren't already moving, but not so bad if you have built up momentum.

 

The gearing in your transmission works with the gear in your rear differential to tailor the power produced by the engine to the demands of moving your truck.

 

The lower the gear (larger numerically) in your rear differential, the easier it is to move your truck forward in all gears.

 

3.42:1, 3.73:1, and 4.1:1 are numerically pretty close, but if you do the math, your engine will turn 20% more rpm in every gear with a 4.10:1 compared to a 3:42:1 differential gear. 3.73:1 is seen as a pretty good compromise.

 

If you are planning on replacing your tires with taller tires, then by all means get the 4:10 gear.

 

Hope all of this wasn't too basic.

piscator Enthusiast

piscator

Posted
  • Author
Posted

Thanks guys! I've got two trucks to call on tomorrow and your help is invaluable.

 

MarkD, That's just a terrific exposition and deserves to be 'stickied' somewhere into perpetuity!! Your 'ten speed bike' analogies are not, 'too basic' -- they're basically clear and well done!

 

Ryan, You and MarkD have 'put the lights on' for me' and I appreciate it. I'm glad you mentioned the gearing in relation to the extra-horsepower, I hadn't considered it.

 

I found a few Sierras with 6 speeds, but the better deals seem to be 4 speeds. Everything's gotta stop somewhere!

 

Buck, Jman, I won't be towing often, so maybe 3.73 is the best compromise.

 

MJB, Vmax, my local launch ramp is 3 miles from my house, so it's not 'long haul' :D The trip up to Maine is, but we only do that a few times a year. I'm not sure it'd be worth gearing the 'daily driver' just for those trips.

 

I haven't taken the bigger boat very far... yet! With a little more boat and and a new truck, I'm hoping to expand my fishing horizons! :lol:

 

piscator

BuckFeverZ Senior Enthusiast

BuckFeverZ

Posted
Posted
Thanks guys! I've got two trucks to call on tomorrow and your help is invaluable.

 

MarkD, That's just a terrific exposition and deserves to be 'stickied' somewhere into perpetuity!! Your 'ten speed bike' analogies are not, 'too basic' -- they're basically clear and well done!

 

Ryan, You and MarkD have 'put the lights on' for me' and I appreciate it. I'm glad you mentioned the gearing in relation to the extra-horsepower, I hadn't considered it.

 

I found a few Sierras with 6 speeds, but the better deals seem to be 4 speeds. Everything's gotta stop somewhere!

 

Buck, Jman, I won't be towing often, so maybe 3.73 is the best compromise.

 

MJB, Vmax, my local launch ramp is 3 miles from my house, so it's not 'long haul' :D The trip up to Maine is, but we only do that a few times a year. I'm not sure it'd be worth gearing the 'daily driver' just for those trips.

 

I haven't taken the bigger boat very far... yet! With a little more boat and and a new truck, I'm hoping to expand my fishing horizons! :lol:

 

piscator

 

You gotta remember Brain will probably read this post, so next time use simpler terms so he can understand what you're trying to convey...oops I mean say. :P

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      I had skimmed through that article when you posted the link and honestly I felt rather defeated in a sense and realized that all these years in changing oil that in fact putting in what I was told was a good quality oil was probably not filtered as well as it should be although the filter put on the engine would be what ( as long as it never went into bypass mode ) would be the final filtering of the new oil that the engine components would first see, but then the filtering media itself is not up to par to what is ideal because a full flow filter would be too restrictive to filter fine enough for the engines best outcome in the long run. Only one of our tractors over the years which was a Versatile with a 855 Cummins had a separate bypass filter, some engine manufacturers did spec a partial bypass system within the main oil filter but I don't believe any other trucks or equipment I was servicing used such a filter. No doubt a product like the Amsoil bypass system is of benefit as long as nothing goes sideways with the extra plumbing and filter such as a rupture/leak that could cause the oil to pump out of the engine ( yes that Versatile had a remote canister with hoses routed to it as well ). With the idiot egr system on a diesel and as a result forcing a lot more soot into the oil, that certainly isn't helping the diesel engines cause or as you pointed out the GDI engine issue with creating more soot and aside from having a fancy secondary filtering system, changing the oil more often helping lower the total soot load.     So oil manufacturing and the end product is not something one can control and I wonder if there are specs on what various oil packaging companies produce in particle count or size. As to the filtering, if the OEM is not designing a filter size and spec that is really what it could be, they too are short changing the end user and so what is the answer. Of course as you say the oil side can only do so much if the air side isn't keeping up its end of the picture and air filters are only so efficient and if in a dusty environment such as farm or construction or driving gravel roads there is a lot of dirt to filter out and some of that ends up into the air stream.    Of course the irony in places like where I am where they dump the salt on the highways but also will mix in some calcium or outright pure calcium for problem road area's, or using calcium as dust control on gravel roads, the vehicle that gets used in that environment may rust out before a properly engineered engine and maintenance finally wears out so one has to face that reality in the rust belt. 
    • GAMark
      Road Master Active Suspension

      By GAMark · Posted

      Has anyone run these on their 2500?
    • Erfar
      Oil Change

      By Erfar · Posted

      have you stuck with dealer oil changes since then? I made the same switch after getting tired of crawling around under the truck, but I’ve found some dealers are way better than others about getting you in quickly. Curious if yours has been good about scheduling or if you’ve had to look elsewhere for quicker turnaround.
    • cherryred21duramax
      Can anyone decode a VIN to determine if this truck has had emissions issues or a recall?

      By cherryred21duramax · Posted

      Thank you.   I am set on a 3.0 Duramax as my previous truck with a Ford Ecoboost had just as many, if not more, "common" issues.  Cam phasers, timing chain issues, 10-speed valve body and CDF drum, emissions issues, etc.  So I figured, why not get 2x the fuel mileage (these things got 27+mpg on every mixed city/highway test drive I put them through) and better towing capability with resale value to boot?   My minimum, shortest trip will be 50 miles 1-way and I regularly go out of state with a travel trailer.  I'm planning on using this for a marketing/event promotion business also, which would require regular towing of trailers for bands, DJs, sound and lighting gear, along with my personal camera gear for filming events.   Looked at other trucks in the $30k+ price range but the issues seem to be everywhere, plus too many with gaudy mods.  I'm literally sticking with RWD trucks because they tend to be actually used as trucks, vs. the 4x4 models I've seen with unsafe lifts, huge tires, and general mods that would affect reliability (I'm wondering if some of them were tuned, hence the aggressive throttle response and hard shifting).   So my goal is to find a stock, 3.0 with 1 or 2 owners, in good physical condition, and decently well maintained.  Can't seem to find that up here, everything in the $27-30k range has had multiple owners, smoke smell, issues, or body damage.  Or the ridiculously modified trucks with 80k miles for under $27k but lots of problems...
    • KARNUT
      OCI, not when but why?

      By KARNUT · Posted

      That’s pretty tough Grumpy. I reread the previous few posts. They all reference oil changes. Much like your last thread. In my humble opinion it keeps things interesting.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...