Trans / Overdrive install

[tgdiver]

Has anyone actually added an overdrive unit or a 700R4 trans on a 3/4 or 1 ton 4x4 truck that has a TH400?

I just spoke with the mech who was getting me a quote, and wow, the price went through the roof! They said that converting from TH400 to 700R4 requires a ton of stuff, including modifying the NP205 trans case. Esentially, the price hit about $4,000.

 

They even mentioned that adding in an overdrive unit between the TH400 and NP205 would require a ton of modifications as well. Moving the NP205, and shortening the drive line, etc. This process also costs about $4,000.

 

Converting to a 5 spd NV4500, would come out about the same at $4,000.

 

I had heard of people adding a 700R4 to 2wd, but not a 4wd.

Has anyone done this?

[C1500]

The price sounds quite high. You would probably be better off finding the tranny / TCase you want from a late model 4x4 and swap the tranny & TCase. You would still have to modify a cross member to support the Tranny/TCase and the length of the drive shafts, because the overdrive trannys are longer than the 400. I have never done it so I don't know all the details.

[99-2door]

You could get a 4L80e from a 93 ( I think) up 4x4 with the floor shift transfer case. They make an independent tranny control computer for using the 4L80e and 4L60e with carbed engines. Of course you would still have to have drive-shafts made.

[BuiltNotBought]

If you get a np208 transfer case you will be good to go.

[Bullstaff]

C1500 hit the nail on the head, Pay a trip to your local junkyards and look for a truck like yours then you can get the tranny, transfer, crossmember, and correct lenth drive shafts. You might have to pull from a couple different trucks to get them. Cutting and splicing drive shafts are tricky if the person doing it doesn't get it perfectly ballanced you would have severe driveline vibrations.