E350 5.8 e40d gears? Need advice on new gear set.
 

Hey all I need to pick some brighter brains than mine here. I have a 92 e-350 chateau with the 5.8l and e40d Im pretty shure, The van has absolutly no guts and cant run in overdrive, Im pretty shure it has 3.55 gears. I want to keep the old thing because its an imaculent rig. Inside and out. Its been a pain in my ass ever since I traded for it. I have had to change hoses thermostats, "I broke the bolts off yea I know I cussed and cussed and it took me 2 weeks to get them out." But Ive chainged the brain box and flushed the system multiple times"cooling" put a flex fan on "no clutch" I mean this rig has no power, unless I run it out of overdrive and then it still dont have much. I dont think its turning enough rpm's to have any power. At about 70 im only turning about 1800 rpm with the 3.55 gears. I am thinking about swaping in a set of 4.56's and that should get me up to about 2400 at 70 ish. these numbers are in overdrive aswell. Do any of the Knowledge able persons here see and serious issue or problems developing with this? The van is the Hd version. :confused::confused::confused::confused:

If the van has had good regular routine maintenance , before getting into changing a lot of parts consider having an exhaust back pressure test done to rule out a restricted exhaust system.

Yea Ive already gutted the converter and put duals from the converter back 2.5 inch with a thrush 1 in 2 out muff.
:cool:

Ok so I ran into a huge issue! I apparently have the dana 61 rear end..... I have found a set of 4.56 gears, But i am affraid to get them because I have been told that you have to custom shim them with some crazy amount of spacing to make it work. I have searched for a whole day on the internet and have only found 1 gear set that says its for the dana 61. From Summit. The gear set numbers are 70907x. it says its a 4.56 gear set for the dana 61. Anyone have any Idea if its just a d60 gear set or if its an actual d61? cause I'm not a machinest nor an engineer. Just a dumb red neck that needs his van to have more grunt, and cant afford to buy a gear set if it wont work... Any help here would be appreciated greatly! I have the axle code 33. which from what I can figure says its the d61 with 3.55 gears.