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How are the 3.55 guys?

1K views 9 replies 8 participants last post by  Tsgs69400 
#1 ·
I was wondering how the guys with the newer trucks were doing with the 3.55 gears compared tomost of us that have the 3.73 gears.
What are the cruising rpms on the freeway like?
Did they change the gear ratios in the tranny?
 
#2 ·
i wish i had 3.55's
 
#4 ·
my truck has a 3:55 diff. i suppose it helps running empty....but l only get 14 running empty and 10 hiway pulling 8000lb trailer[mountain pulling]....i used to get 15 with my 7.3 pulling the same trailer.........BUT I LOVE THIS TRUCK AND WOULD NOT TRADE IT...:thumb:
 
#6 ·
Mine was excellent with 3.55's and 35s. You'd probably be ok with the 37s. The new 6.7's are going to come with 3.31's standard!
 
#7 ·
Forgot to mention my truck runs great on the highway (not towing), I think it runs around 2K rpm @ 65mph. I only have 330mi on it now and obviously haven't towed anything yet....

Mine was excellent with 3.55's and 35s. You'd probably be ok with the 37s. The new 6.7's are going to come with 3.31's standard!
Good to know, thanks for the info :thumb: (sorry didn't mean to hijack original thread). Wow, I didn't know the new trucks will have 3:31's..
 
#8 ·
I have 3.73, I would be scared of the 3.55's. Mine is honest 15/ 16 MPG empty on the highway, not to bad for a 9,000 lb monster!

Oh ya, and about the 6.7's having 3.31's, that is irrelevant unless you know the output shaft speed of the transmission....
 
#9 ·
I'm not sure about the gear ratios in the tranny (I would think they'd be the same) but I'm happy with the 3.55 gearing in the back. My truck is running on stock 20" wheels and the tach reads at about 1,500 RPM at 60, 1,600 at 65 and about 1,700 at 70. During my drive from CA to TX, I averaged 16-17 MPG at 70 MPH. She was new so I didn't want to "push her" to the 80 MPH speed limit in west TX.
 
#10 ·
Well considering my rpms at speed then they didnt change the tranny ratios.
It makes sense to me that you 3.55 guys are having mileage issues while towing because the engine is not able to run at it's torque peak of 2000 rpm.
With my 3.73s i can run about 2000 rpm at about 70-72 mph. I can see the 3.55 gears being good with the 6.7 because it has a lower torque peak of like 1600 rpm I think.
I wonder what the track times are like with the 3.55 trucks. I'd bet they would be better.
 
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