I bought a 07 dually today and my dealer said there were two G56 tranny's made. One with AD gearing 6th is 0.79 and AE gearing 0.74 gearing. He didn't know what mine would have in it and I wont see it for another week or two is there any way to know. He said the 2006 models had the AD for sure but didn't know about the 07s at all.

 

My 2007 has the lower geared AD just like the 2006 trucks. I think the higher AE's are an upgrade on the 2007.5 model from complaints about the g56 being geared too low.

 

THAT would have saved me $3000.... (for the Gear Vendors OD)

 

I wonder if you can get the parts to make your G56 AD in to a AE and I wonder how hard it would be to convert it?

 

Probably not too hard Thundercloud if you've ever been into a manual trans before but getting the gear might be another matter altogether. They're awfully new.

AE's a slight improvement but I think they're still too high. The 07.5's run about 70mph @ 2200 rpms versus 65mph @ 2100 for our 06, 07 trucks. We're closer to the sweet spot running 75mph @ 1850 rpms in 6th over plus our 6th gear is a little stronger than theirs.

 

So how do you know what gearing you have? can you tell by the VIN#?

 

The last two letters on the bar code lcated on the right side of the transmissin will be AD or AE. just wish I had my truck to see.