[Goatash]

At the moment I do 100 km/h and it’s reving at 2000 RPM. Besides, switching the G 56 to the AE edition (the better gear ratio)
, Is it possible to put a 3:42 gears in the front and rear differential? Also, is it possible just to add bigger tires in the stock ones?
Will it make that big of a difference doing either of those?

 

[19 Badger]

At the moment I do 100 km/h and it’s reving at 2000 RPM. Besides, switching the G 56 to the AE edition (the better gear ratio)
, Is it possible to put a 3:42 gears in the front and rear differential? Also, is it possible just to add bigger tires in the stock ones?
Will it make that big of a difference doing either of those?

This is something I am kicking around as we speak. Have had the truck since new and has always bothered me, just could never justify changing perfectly good parts. 17 years later, it is easier to justify, lol. I don't drive it everyday like I used to, only when on a longer trip now. I try to cruise down the highway at about 1850 rpms, which only puts me at 60mph I did go to a slightly larger tire(285/70r17), can't go any bigger due to flatbed clearance. Looking at doing the 3:42 and free spin kit in the front since I am due for front end wheel bearings and axle u-joints anyway. May as well drop in a front locker while I'm in there.... Should give me another 5-6mph at same rpm and would have a 2 wheel low option with the free spin add on.

 

[JR the Mechanic]

3.42 gears would be nice, that is what I have in my truck, but it wasn't cheap. I swapped from 4.10's to 3.42's and replaced all bearings in both diffs while I was in there, it cost right around $2000 for just the parts. Swapping differential gears would only gain about 10kms/hr, swapping transmissions would only gain about 7kms/hr, and swapping for 1 size bigger tires would gain about 3kms/hr.
The 0.79 overdrive ratio of that G56 is a bit pathetic. The other G56 has a overdrive of 0.74.
At 2000 rpms in 6th (0.79) with 285/70r17 tires and 3.42 gears you would be at about 112kms/hr.
At 2000 rpms in 6th (0.79) with 265/70r17 tires and 3.42 gears you would be at about 109kms/hr.

At 2000 rpms in 6th (0.79) with 285/70r17 tires and 3.73 gears you would be at about 103kms/hr.
At 2000 rpms in 6th (0.79) with 265/70r17 tires and 3.73 gears you would be at about 100kms/hr.

At 2000 rpms in 6th (0.74) with 285/70r17 tires and 3.42 gears you would be at about 120kms/hr.
At 2000 rpms in 6th (0.74) with 265/70r17 tires and 3.42 gears you would be at about 116kms/hr.

At 2000 rpms in 6th (0.74) with 285/70r17 tires and 3.73 gears you would be at about 110kms/hr.
At 2000 rpms in 6th (0.74) with 265/70r17 tires and 3.73 gears you would be at about 107kms/hr.

 

[19 Badger]

3.42 gears would be nice, that is what I have in my truck, but it wasn't cheap. I swapped from 4.10's to 3.42's and replaced all bearings in both diffs while I was in there, it cost right around $2000 for just the parts. Swapping differential gears would only gain about 10kms/hr, swapping transmissions would only gain about 7kms/hr, and swapping for 1 size bigger tires would gain about 3kms/hr.
The 0.79 overdrive ratio of that G56 is a bit pathetic. The other G56 has a overdrive of 0.74.
At 2000 rpms in 6th (0.79) with 285/70r17 tires and 3.42 gears you would be at about 112kms/hr.
At 2000 rpms in 6th (0.79) with 265/70r17 tires and 3.42 gears you would be at about 109kms/hr.

At 2000 rpms in 6th (0.79) with 285/70r17 tires and 3.73 gears you would be at about 103kms/hr.
At 2000 rpms in 6th (0.79) with 265/70r17 tires and 3.73 gears you would be at about 100kms/hr.

At 2000 rpms in 6th (0.74) with 285/70r17 tires and 3.42 gears you would be at about 120kms/hr.
At 2000 rpms in 6th (0.74) with 265/70r17 tires and 3.42 gears you would be at about 116kms/hr.

At 2000 rpms in 6th (0.74) with 285/70r17 tires and 3.73 gears you would be at about 110kms/hr.
At 2000 rpms in 6th (0.74) with 265/70r17 tires and 3.73 gears you would be at about 107kms/hr.

Thank u for that data JR, very helpful. Since I already have front end work planned, it only makes sense to up the gear ratio to 3:42 while in there. Yes, expensive and more labor intensive. Diesels are an expensive game.

 

[JR the Mechanic]

Thank u for that data JR, very helpful. Since I already have front end work planned, it only makes sense to up the gear ratio to 3:42 while in there. Yes, expensive and more labor intensive. Diesels are an expensive game.

I think you will like it, I debated between 3.73 and 3.42 gears on my but went with 3.42's and really like it and I have a better overdrive of 0.72 (mine runs about 1700rpm at 100kms/hr or 62miles/hr).

 

[Goatash]

3.42 gears would be nice, that is what I have in my truck, but it wasn't cheap. I swapped from 4.10's to 3.42's and replaced all bearings in both diffs while I was in there, it cost right around $2000 for just the parts. Swapping differential gears would only gain about 10kms/hr, swapping transmissions would only gain about 7kms/hr, and swapping for 1 size bigger tires would gain about 3kms/hr.
The 0.79 overdrive ratio of that G56 is a bit pathetic. The other G56 has a overdrive of 0.74.
At 2000 rpms in 6th (0.79) with 285/70r17 tires and 3.42 gears you would be at about 112kms/hr.
At 2000 rpms in 6th (0.79) with 265/70r17 tires and 3.42 gears you would be at about 109kms/hr.

At 2000 rpms in 6th (0.79) with 285/70r17 tires and 3.73 gears you would be at about 103kms/hr.
At 2000 rpms in 6th (0.79) with 265/70r17 tires and 3.73 gears you would be at about 100kms/hr.

At 2000 rpms in 6th (0.74) with 285/70r17 tires and 3.42 gears you would be at about 120kms/hr.
At 2000 rpms in 6th (0.74) with 265/70r17 tires and 3.42 gears you would be at about 116kms/hr.

At 2000 rpms in 6th (0.74) with 285/70r17 tires and 3.73 gears you would be at about 110kms/hr.
At 2000 rpms in 6th (0.74) with 265/70r17 tires and 3.73 gears you would be at about 107kms/hr.

Thank you for so much info there that really helped

 

[jim.killen123]

I think you will like it, I debated between 3.73 and 3.42 gears on my but went with 3.42's and really like it and I have a better overdrive of 0.72 (mine runs about 1700rpm at 100kms/hr or 62miles/hr).

Yea well it depends I guess what your doing w

This is something I am kicking around as we speak. Have had the truck since new and has always bothered me, just could never justify changing perfectly good parts. 17 years later, it is easier to justify, lol. I don't drive it everyday like I used to, only when on a longer trip now. I try to cruise down the highway at about 1850 rpms, which only puts me at 60mph I did go to a slightly larger tire(285/70r17), can't go any bigger due to flatbed clearance. Looking at doing the 3:42 and free spin kit in the front since I am due for front end wheel bearings and axle u-joints anyway. May as well drop in a front locker while I'm in there.... Should give me another 5-6mph at same rpm and would have a 2 wheel low option with the free spin add on.

I have a 95 4x4 with 3.54 gears and it originally had a automatic which I hated from day one .so I bought a g56 and I had no idea there was two different overdrive ratios. To be honest if I had know about the Ford 6 speed working in my truck I might have gone that way as I think it's. 72 . But anyway mine is a .79 . I went to the 385/75/17 and that really helped . My truck does OK now . I will say the .79 does OK towing . I bought the transmission and had it rebuilt and the tc at the same time with a bm shifter , dual disc Val air , one piece aluminum drive shaft. . My truck came stock with a lot shorter tire and the tires I have now really helps . I like to have a higher overdrive but my truck gets decent mileage now if I drive it easy

 

[johnstangl]

Yea well it depends I guess what your doing w

I have a 95 4x4 with 3.54 gears and it originally had a automatic which I hated from day one .so I bought a g56 and I had no idea there was two different overdrive ratios. To be honest if I had know about the Ford 6 speed working in my truck I might have gone that way as I think it's. 72 . But anyway mine is a .79 . I went to the 385/75/17 and that really helped . My truck does OK now . I will say the .79 does OK towing . I bought the transmission and had it rebuilt and the tc at the same time with a bm shifter , dual disc Val air , one piece aluminum drive shaft. . My truck came stock with a lot shorter tire and the tires I have now really helps . I like to have a higher overdrive but my truck gets decent mileage now if I drive it easy

don’t wanna hijack the thread.. just a question. but i got a 99 with an automatic trans and 3.55 gears. been on the lookout for a manual swap. i haven’t heard about the ford 6 speed. i was planning on a nv4500. is the ford 6 speed a common swap?

 

[JR the Mechanic]

I have the transmission from a ford, it is the ZF6, Chevy used a slightly different version of the same transmission behind the Duramax. Adaptors can be found fairly easily, the cheapest is the one from Wildhorse Mfg. (it is made of steel). they all use the ford starter. the zf6 overdrive is 0.72.

 

[jim.killen123]

I have the transmission from a ford, it is the ZF6, Chevy used a slightly different version of the same transmission behind the Duramax. Adaptors can be found fairly easily, the cheapest is the one from Wildhorse Mfg. (it is made of steel). they all use the ford starter. the zf6 overdrive is 0.72.

It seems like a good choice as the automatic is .69 and the g56 is . .74 or .79 ..the zf6 is a good choice depending on what your trying to do towing my .79 and the tall tires of the 285/75/17 is not far off from the original tires of the 245/75/16....if I were starting over yea I would have done the zf6 ..

 

[zebra]

I have the transmission from a ford, it is the ZF6, Chevy used a slightly different version of the same transmission behind the Duramax. Adaptors can be found fairly easily, the cheapest is the one from Wildhorse Mfg. (it is made of steel). they all use the ford starter. the zf6 overdrive is 0.72.

to reduce the chaff in your searches: its a ZF S6-650... not to be confused with the ZF S6-40 used in the 89-96 corvettes (also colloquially called a ZF6 and of which there were also two versions).