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-   -   G56 gearing compared to a 68RFE or Aisin with same axle ratio (https://www.cumminsforum.com/forum/4th-gen-powertrain/2504147-g56-gearing-compared-68rfe-aisin-same-axle-ratio.html)

jdub454 06-23-2019 06:41 PM

G56 gearing compared to a 68RFE or Aisin with same axle ratio
 
So a while back I read somewhere on here about how having a G56 will change the gear reduction. Basically what was stated is that if you have a G56 with 3.42 and a 68RFE with 3.42 the G56 will reduce your gearing to where it's more like drive a 68RFE that has 3.73's. My previous truck started with 3.42's and I swapped to 3.73 for better towing. It was an auto. Even with 35's it towed much better with the new gearing. New truck is an 18 3500 bone stock G56. Can anyone that knows about this lend me more insight. I've done Google searches looking for any more info as well as try to find the thread but it was quite awhile back I read it.

the man in black 06-23-2019 07:11 PM

The gear ratios in the 68 and g56 are different. What is typically said is that in 6th the g56 with 3.42s is similar to the 68 with 3.73s. What you would need to do is look up the ratios for both transmissions, multiple the ratio for each gear by the axle ratio. That gives the final gear ratio which you can easily compare.

What is your question? The 3.73 with the g56 will pull harder than the g with 3.42s

dillonjm 06-23-2019 07:17 PM

G56 gearing compared to a 68RFE or Aisin with same axle ratio
 
Pulled from a quick google search:

https://uploads.tapatalk-cdn.com/201...daa729c4c0.jpg

https://uploads.tapatalk-cdn.com/201...86a583db55.jpg

https://uploads.tapatalk-cdn.com/201...63510724c4.jpg

The G56’s highway RPM, assuming all else is the same, will be higher than the other two transmissions.

Driveability is a different discussion as all three transmission variants carried different engine tuning.

What is your question?

the man in black 06-23-2019 07:20 PM

2.53, g with 3.42s in 6th

2.34, 68 with 3.73 in 6th

jdub454 06-23-2019 07:41 PM

2 Attachment(s)
I guess what I'm asking is if having a G56 with 3.42 is the equivalent of having a 68 with 3.73's because of the way the gears are reduced. Does that mean a G56 equipped truck with 3.42 will pull just as good as a 68 equipped truck with 3.73? From my understanding a manual transmission looses less torque and HP than an auto does delivering power to the ground.

dillonjm 06-23-2019 08:01 PM

That is typically true. Manuals typically lose less to the wheels.

You can do a rough wag.

660x.85= 561
800x.80=640

However, it isn’t entirely accurate as the tuning generates peak torque at different spots, etc. so there isn’t a real good way without closely analyzing the graphs to get that data.

All this said, it will pull fine. You’re overthinking things.

jdub454 06-23-2019 08:04 PM

I've pulled with my G56 truck a few times and it does great. I was more curious than anything. My favorite part is having the EB work all the way till I completely stop. I appreciate the insight. Thank you.

ridofpwrstroke 08-23-2019 06:57 PM

The manual trans only has one OD. The autos have 2. My options when I bought my truck. If I got the aisin with 4.88's, it would pretty much be identical if I got the manual with 4.10's. I opted for the auto and some days I regret it. But towing with the aisin and 4.88's is a dream when towing heavy.

the man in black 08-23-2019 11:52 PM

I've have the g56 with 3.42s and 3.73s, the 3.42s are horrible for towing more then 7-8k ish. 3.73 get the truck rolling and keep it going so much easier than the 3.42s. 3.42s make the truck a rocket but not good for towing imo. I'm probably going to swap for 3.73 next year or so.


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