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Dropping to 3.73s from 4.10s

Can Can

Can Can

Pusher Man
Joined
Feb 17, 2000
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Location
Cochrane, Alberta, Canada
Mildy rowdy 454 with a 205/400 combo. I tow 5K pounds all summer long. As it's set up right now, the truck does MORE than fine.

Would dropping my ratio to 3.73s from 4.10s have any downsides?
 
Recalibrating speedometer, cost, and a little more leverage on your transmission are pretty much the only downsides.

My guess would be that you will get better mileage while empty and worse mileage while towing with the 3.73's.
 
3.73's is what I have in my K5. Well, currently, it's been out of commision for a while during a rebuild, but I drove the truck for 4 years w/3.73's, I towed a 4place enclosed sno-mo trailer with it, no problems. Weight of it was probably somewhere around 4000lbs.
My feeling is, if your not doing hard core rocks with it, 3.73's is a good ratio to have, especially if the rig see's a fair amount of highway and you don't have an overdrive.

I got pretty consistent mileage (engine was a pretty stock 350) around 14-16mpg (that's 17-15 l/100km for you) or so, depending on what i was doing. Even towing the 4-place in 4wd, I never got less than 14.

Aside from the mileage, it's better for the engine not to be constantly revving that high.

What tire size you running?
 
That's kinda why I'm thinking along these lines. Swapping in a 4l80e or installing a Gear Vendors unit would be a cool way to go, but it would take me 20 years to make my money back seeing that I only put on about 1000 miles a year.

My main concern is that my RPMs are right around 3000 at 60 MPH, and it would be nice to get them down to the 2700 range at highway cruising speeds. Like I said, the 454 has MORE than enough power and torque to handle the weight with the 4.10s- I can't imagine that 3.73s would cause me any problems.
 
CanmoreK5 said:
That's kinda why I'm thinking along these lines. Swapping in a 4l80e or installing a Gear Vendors unit would be a cool way to go, but it would take me 20 years to make my money back seeing that I only put on about 1000 miles a year.

My main concern is that my RPMs are right around 3000 at 60 MPH, and it would be nice to get them down to the 2700 range at highway cruising speeds. Like I said, the 454 has MORE than enough power and torque to handle the weight with the 4.10s- I can't imagine that 3.73s would cause me any problems.
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Most of your heavy duty pick up's with big gas and diesel engines use 3.73's now days.........
 
You should be fine, out of all the 1 tons we have at work. If they are a big block they are running 3.73s or somethin close to it, if they are a small block they are running 4.10s. And for the record a Vortec 350 with 4.10s had of stump pulling power down low but isnt worth a damn on long grades unless youve got it in 3rd gear(5 speed) and wound up to about 3500 or above
 
Geez can can....gear swaps are expensive also..ding-dong.
What we need to do is looky at the 4L80E route....i have a
complete bumper to bumper harness and ecm from a 91 R2500.
But i do believe there is a rumored manual valve body kit out
there somewhere....so...quit trying to spend your hard earned
money on something like that right now so you can make sure
there is bread in the house when friends drop by from the states
(lol...lil inside humor there.) I'm sure given enough time and patience
something 4L80Eish might turn up...ck5 is a big world with a lot of
reach....

So..lets recap...
1) Quit worring about it right now...its not like your going to drive to BC and back to canland to do a gear swap in that cold....

2) Adhearing to 1 helps you finger what adapter is needed to mount the 205 to a 4L80E one year only adapter....look for a repop by someone...

3) Decide manual valve body or run the electtronic version and we tweak your harness to have the newer ecm to support the 4l80e...while i scrounge the trans somehow....

DW
 
I'd leave it alone, Can Can... 3.73s and 4.10s aren't really that much of a difference, just one ratio apart. Spend the money for something better on what your truck needs.... 14BFF and a D60 sounds good..
 
There's 3.90s out there too. TH350, NP208, 3.90s & 34s is a good compromise for me, without going to 4sp auto, and that would mean gear change again.:D
That's without towing.
 
BadAss90K5 said:
I'd leave it alone, Can Can... 3.73s and 4.10s aren't really that much of a difference, just one ratio apart. Spend the money for something better on what your truck needs.... 14BFF and a D60 sounds good..
Click to expand...

he has those stock in the k30 3+3 :D
 
CanmoreK5 said:
Not when there are 6 of them.........:doah:
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This is funny. Reading the replies of others and some not knowing you are talking about your new tow rig. :haha: :haha: :haha:

If it were me, I'd go with 4.10's and an overdrive of some kind. Preferrably the 4L80E.
If you were gonna do some aftermarket OD, I'd just as well spend the money on the 4L80E and keep the GM all GM.

Of all the 1/2, 3/4 and 1 tons I've had or torn apart, most of them seemed to have higher miles on them when they were equipped with 3.73 gears. Heck, the red flatbed K30 in my shop right now has over 200K on it and its stock with 3.73's.
I'm not sure if I would do a gear swap myself, per se. I like the 3.73 ratio for street and highway duties as it seems to be almost perfect. Adding OD would probably run better if it had 4.10's since it would raise the RPM's up slightly but not much.

Too bad your rig don't have the 465 tranny.
 
There is just not much difference between 3.73 and 4.10 gears (about 9%).....it's a lot of money to spend for a very small change.

You really can't even compare 3.73 vs. 4.10 gears to installing an overdrive like the 4L80E. Having the overdrive gear (25%) does make a big difference.
 
Sounds quite a bit like my dads truck. Overcammed 454/465/205/4.10's, but he has a GV unit on it as well.

Doesn't drive it much, but the 454 at freeway speed is STILL turning (to us) very high RPM's, certainly not necessary when he's empty. He does tow a 10,000# trailer with it once a year.

He's got a 14FF spare that is his disk brake buildup rear that happens to be 3.73, I suggested he put it under the truck as-is, to see if it was worth leaving the 3.73 in it, and swapping the front when one is found.

Only diff is the TH400 not having the super low first, but I doubt there is really a huge difference for starting out, since it's an automatic.
 
I doubt you would have problems with that ratio . I have towed more 5000 pounds give or take several times with my K5 when it was on 3.08's , 33's , with a lowly little 305 .
 
The 3.73's will still be OK with the BBC. I've had them with a 350, and they were disappointing when combined with 285's. That being said, I'd leave the 4.10's in there, and start looking for 4L80 stuff, if you wait and scrounge I think you could piece together a setup for around a grand. The GV units are very expensive, not sure how plentiful they are used, but combined with a TH400 would be the best option for towing. The manual valvebody exists, but is probably not the best option for a towrig. I'm thinking about running one of the quadzillas in my 68 Nova behind a built BBC.

http://www.the-transmission-center.com/
 
3.73s just dont seem worth it. Liek you said you only drive around a 1000 miles a year so I just cant see the justification...
 
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