i have an 84' Z28 with the LG4/auto trans combo. ive read that a mid-year change was made to the 700R4 that increased the spline count from 27 to 30. was there a specific date when this happened, meaning i can look up the build date of my car and know which version i have? or to know for sure would i have to drop my tranny?

the reason im asking is cause i want to use a stock torque converter from a GN. they stalled around 2000rpm and would be a stronger alternative to the S10 converter (which didnt last long in my old 89' Vette... i wont use one of those again). apparently, 2004Rs all had 27 splines, so if i had the older version of the 700R4, a GN torque converter should work

any help would be greatly appreciated

 

You should have a 27 spline converter. They didn't change to the 30 spline version until 87 or 88.

 

I have not yet run across a 30 spline 84 trans. I have rebuilt units made late in the model year that were still 27 spline. I would also like to know the date of the changeover. My gm books contain every other upgrade and the date they occured. The 27-30 spline changeover date is not listed.

 

GM says 87 and they also changed the case as well that year.

 

I don't actually have it in writing anywhere, but I've always heard 87 was the changeover year as well. I'm sure Dana from Pro-Built Automatics would be able to verify that. Maybe he'll chime in on this thread.

 

85 and up have 30 spline.

 

I rebuilt a 700R4 that came from an '84 impala... It was a 30 spline.. So it could be either one... '85 and up is 30 spline though... '87 was a big changeover year for many other things..

 

i know for the 88 model year they changed the case apparently, however, im concerned about the spline count changeover

i looked up a few aftermarket torque converters in jegs & summit and it lists 2 different part #s for each brand/kind of converter for the 700R4 - those made from 81-84, and those made from 84 & up. if that info is correct, then there WAS a changeover to the 30 spline trans somewhere in the 84 model year. also, it lists the 81-84 converters for all 700 and 200 series transmissions, which means my assumption that i could use a GN or similar 2004R converter in an earlier 700 trans is correct

i guess theres no concrete "cut-off" date as to when the spline count was changed, so the only way to know for sure is to pull the trans

 

It's 85+ for the 30 spline converter. Not to say a late model 84 would not have one but your going to have to pull the transmission to be certain.

 

for the v-8 transmissions, some '84 might have 30 spline input, buit was definite in '85 and up. the v-6 retained the 27 spline(with the exception of the 4.3 liter)