LS Swap Question

[DBear]

Originally Posted by Richard

Bought my 94 with 3.42's (4l60e) because I lowered it and installed 315/40/17 tires. Got tired of that and lifted it. Installed a skinny 32" tire. Was a bit sluggish after that and went in and out of OD a lot. Not to long ago installed the 3.73's because pinion broke. Better performance and the extra 150 rpm is not even noticed on the highway (no change in milage). Almost wish I had gone with the 4.10s. Personally, I would install 4.10's with your scenario, will be more like my current setup. 3.73's will be about 1800 rpm with your tires. The 4L80 has a bigger gaps from OD to 3rd and 3rd to 2nd than the 4L60. So, avoiding the rpm increase with down shifts will make highway driving more comfortable.
Have used Yukon gears twice and had no problems yet. Have another set of 5.13 Yukon's I will install in the AAM 11.5 at the back of my 72 which will have 37" tires. LSA powered and a 6L90 trans.
Maybe try the 4.56 gears with the OD trans, you may be surprised. Only about 300 rpm at cruise over the 3.73 I would guess. You are driving a brick wall, so milage will probably not change with any gear.

Just looked in my bone pile LOL, and I do have a 14 bolt with 4.10's with the correct spring pad spacing for my K30. I think I will go with the 4.10's like you are suggesting, and will only have to re-gear the front Dana 60.