700R4 question

[apache]

Is there a particular year in the eighties the 700r trannies were improved? Seems every early 80ies K5 I stumble on had or has a bad trans. Im sure one can be built to handle mass ponies but im talkin about factory installs specifically.

 

[cuervo]

None that I know of.

 

[lectric80]

The update to make them slightly better occured in 88. However, 700's are very commonly replaced due improper adjustment of TV cables, as well as heavy abuse by owners. My first experience with a 700 was in my 88 Astro, and it made it well over 300k before it went out. I chalk it's failure up to the heavily upgraded 4.3 I put in front of it and the long service life.

 

[cuervo]

What was changed in the 88+ versions?

 

[ciffer]

i am pretty sure the major change happened in late 87 with a change to the valve body.

here is an article from Hot Rod Magazine about the 700r4.

http://www.hotrod.com/techarticles/113_0704_700_r4_transmission/valve_body.html

 

[4X4HIGH]

What was changed in the 88+ versions?

Different case, auxillary valve body and other deeper internal changes. The biggest change was the case and auxillary valve body though.

 

[cabledawg]

lectric80 hit it with the TV cable being the culprit most times. I bought a 90 Burb with 130k and the dealer replaced the trans with a junkyard special because the original lost reverse. That one lasted a year and 30k miles before it started losing first and all forward gears shortly after. New trans installed, lasted barely a year before it was blowing pan seals on a monthly basis (never found out why).

Bought my 88 Burb with 87k and it was still working when I pulled it at 120k to swap in a SM465 for towing. TV cable went out on that one and took me a few tries to get the adjustment right. Too loose and the trans wont shift out of 1st; too tight and it shifts too soon and really hard.

When I was doing my research, I found that there is a valve body to replace the stock one that maintains 200psi. this aloows a little more grace for a porr adjustment, but doesnt replace the TV cable. I also read that the Corvette servo is a good upgrade, but I'm not exactly sure why its different (better holding on the bands?).

 

[cuervo]

i am pretty sure the major change happened in late 87 with a change to the valve body.

here is an article from Hot Rod Magazine about the 700r4.

http://www.hotrod.com/techarticles/113_0704_700_r4_transmission/valve_body.html

Very nice link! Thanks.

 

[Kjunky5]

I also read that the Corvette servo is a good upgrade, but I'm not exactly sure why its different (better holding on the bands?).

The corvette servo has a larger fluid apply area so, yes, more holding power on the band. There's only one. So just to confirm. Valve body, case, input shaft spline, pump, input sprag (which also removes the need for one of the thrust washers), low/reverse piston. It goes on and on but you want to find one 87 and later.