Overdrive trans swap

**PrestonM** · 08-04-2009, 05:13 PM

Alright guys, here's the deal. I have an 84 SWB step side half ton. It has a rebuilt 350. I know that it still doesn't have the factory 2.78 rear end like the sticker says, and I want to turn this into a daily driver. I am getting the funds together as we speak to fix the air conditioning and get some decent used rims(which are hard to come by) so that I can daily drive it. My question is this: What is the most cost effective and easiest way to put an overdrive transmission in my truck and which one would you all suggest? My first instinct is the 700-R4. Ideas anyone? I tried the search tool, but I can't seem to put the right words in there or something as all it does is give me a thread for changing a 700 to a 350.

P.S. I know that I will probably have to get a different drive shaft too. Any help on that would be greatly appreciated as well.

**tbplus10** · 08-04-2009, 07:56 PM

A friend of mine recently had a local shop put a rebuilt 700r4 in place of his tired 350, it cost him around $500 for the swap with 12mo 12K mile warranty.

**PrestonM** · 08-04-2009, 09:52 PM

Is it a job that a shadetree mechanic can tackle, or just take it to a shop? What do i need besides the tranny?

**Jimmiee** · 08-05-2009, 09:33 AM

You will need the following:

1. 700R4
2. Torque Converter.
3. Flex plate unless yours is drilled for a 700. <2 sets of bolt holes>
4. TV Cable
5. Dip Stick
6. Dust cover.
7. Drive shaft shortened.
8. Lock-up kit installed in 700. <otherwise the trans will overheat>
9. 12V supply from ign. source to transmission.

This is a good swap and you will have a lower low and overdrive.

**PrestonM** · 08-05-2009, 09:53 AM

Thanks for the info Jimmiee. I am looking at a shop that has a rebuilt 700R4 for 250 bucks. Where do I get the lock up kit and what does it do?

**Jimmiee** · 08-05-2009, 02:08 PM

Originally Posted by PrestonM

Thanks for the info Jimmiee. I am looking at a shop that has a rebuilt 700R4 for 250 bucks. Where do I get the lock up kit and what does it do?

You can buy several kinds but the one that works best uses a vacuum switch. This is a nice feature as it unlocks and downshifts the transmission with part throttle just like a stock 700 works. You can also wire it up where it locks up when it hits 4th gear but this presents a harsh 3-4 shift and you have to floor it to downshift into 3rd to unlock the converter. This mod can be done for about 10 bux or less. Even free if the 700 has a 4th gear pressure switch. Some do, some don't.

Here's a link to the kit I would use.....Click