transmission swap

[pausma]

I have a '91 D350 with dual rear wheels and a 3 speed automatic. I am wondering if it is possible to swap out the 3 speed for a 4 speed automatic. Has anyone done this previously? The 4 speed I am currently looking at is out of a '93 3/4 ton Dodge Cummins. My main reason for wanting to swap the trannies is so I have a 4th gear for highway driving. I don't like to rev my engine so high while driving down 4 lane highways with my 3 speed.

 

[DVolk]

You could install one from a newer truck although you might need the computer and wiring to controll it , if your transmission works good you might be better off to install a gear vendors unit then there is no extra electronics or computer unless you go to a older allison , of which means new adpter plate etc ...

 

[Philip]

A gear vendors is $3K give and take a little. Its not worth it.

You can use eather a 518 out of a 92/93 Dodge. That gives you just OD.

A 94/95 Dodge diesel used a 47RH. Its harder to find and cost more than a 518 will used. It would require a different engine adapter/ starter. It would give you OD and a lockup converter.

For control of OD just use a pressure switch installed into the governor test port. Most use a adjustable pressure switch. Then you just dial the switch to bring in OD at the speed you want.

Now using a pressure switch will bring the OD in at the same speed every time. It will drop OD at the same speed every time..

 

[RSchwarzli]

Been there with the Gear Vendors part of this convo. The 727 is a non lock up TC. Without lockup, the GV only adds to the slippage so you wont get enough out of the money you spent.

Are you opposed to a standard trans? That is likely your best bet.