400 to 700r4 swap?

[Sawlog]

I have a chance to by a 1990 2wd Silverado. I has a 350 and 700r4 tranny.
Can I put that tranny in my 1969 c10? I would love to have overdrive and run a lower rear gear.
Thanks, also are the motors any good? I think it's a tbi.

[AussieinNC]

700R4 from 1990...assuming its a stocker....is a serious backward step...IMO...

1990 350's TBI ,,,, again, no info on condition...but unless you have a really sick 350 in the truck now...I would stick with what you have...

1990 350 wont have mechanical fuel pump capability, they have poor flowing crack prone heads and lousy horsepower...

If you want my suggestion...aim for a 200R4 auto or even better....4l60e...you will need a trans controller, and new driveshaft...but you get a much stronger trans from the get go...

Just my two cents worth...

[dagnabbitt]

Originally Posted by Sawlog

I have a chance to by a 1990 2wd Silverado. I has a 350 and 700r4 tranny.
Can I put that tranny in my 1969 c10? I would love to have overdrive and run a lower rear gear.
Thanks, also are the motors any good? I think it's a tbi.

If you want O/D, the 700r4 is what you want, provided that you aren't doing a lot of towing etc. And 1990 is one of the best year to get it. 30 spline, pre-electronic.

[70 cst]

I have a 91 700 r4 in my 72 that came out of a van. I had it rebuilt and purchased a vacuum operated lock up switch and I think it's the best thing since sliced bread. I would probably stay away from the tbi 350 for the same reasons stated above.

[67 chevelle]

Originally Posted by AussieinNC

700R4 from 1990...assuming its a stocker....is a serious backward step...IMO...

1990 350's TBI ,,,, again, no info on condition...but unless you have a really sick 350 in the truck now...I would stick with what you have...

1990 350 wont have mechanical fuel pump capability, they have poor flowing crack prone heads and lousy horsepower...

If you want my suggestion...aim for a 200R4 auto or even better....4l60e...you will need a trans controller, and new driveshaft...but you get a much stronger trans from the get go...

Just my two cents worth...

Total agreement 700r4/4l60 are junk ,,,, 2004r would be better but Ill never use any of these transmissions again ,, get a 4l80 ,, or keep the turbo 400

[Mike C]

Plenty of TH700R4’s out there that handle more than 500 hp all the time. Once again, with junkyard stuff you aren’t sure what you are getting. But if it works now, it should work in your truck as well. I am a TH200 4R fan as well, but cheap or free and run it ‘til it breaks always works in my world. The 4L80E is the choice if you are making big power with a big motor, but the tall first gear, less overdrive and requiring stand alone electronic controller are deal breakers for me for a mild combo.

Many of the early TBI motors still have mechanical fuel pump capability. You will just have to look and verify. My machine shop buddy and I were just talking about this last week. His ‘95 Chevy Z71 has a 5.7l with the blockoff. The one piece seal 265 HP Mercruiser in my ‘94 Malibu ski boat has a one piece seal block and it has a mechanical pump as well.

[MARKDTN]

350 TBI is no powerhouse but are good sturdy motors. You can install using the harness, but you may be better off with a retrofit harness. You can use your original accessories or you can keep the serpentine belt setup and make new a/c lines (or a delete). I would swap the CS130 alternator for a CS144. Use your original exhaust manifolds and add an O2 sensor. Pretty much all you need is an external fuel pump or use a later tank (like a 2.8 S10 Blazer) with a pump in it.

1990 is the improved version of 700R4 so good. There is nothing wrong with a 700R4. It is the basis for the 4L60E a few years later. Most problems with 700R4 retrofits are due to not adjusting the TV cable.