The Stovebolt Site Forums The Shop Area Engine Shop 700R4 opinion

I have a '88 vintage 700R4 tranny with lock up converter that I intend to swap into my '68. The truck has a 350 4bolt main that will be mildly modded (intake, serpentine belt setup, electric fans)It will never be heavily loaded or used to tow anything.
Before I install the tranny, I took it to a local shop that has the best reputation for fair deals and standing behind their work in my area. The owner of the shop suggested some minor mods be made to the tranny all of which one sounded reasonable to me. The one I'm having trouble getting my head around is the elimination of the lock out feature. He says it only saves about 300 rpm, and isnt worth the trouble in added fussiness of shifting, and added heat to the unit. I thought that the lockout saved heat by eliminating the slippage in torque converter. Is this guy trying to pull something over me, or does he seem reasonable?
He's giving me a new, higher stall converter(presumably a non locker), changing some bands, adding a Vette servo, and a trans go shift kit, also changing all seals, and "soft" parts at a cost of $950.00. The cost doesnt bother me so much as the question about eliminating the lockup, is it the right thing to do?

Iam not sure what the cut off years are but the earlier 700R4's were week, be carefull, have also been told to get a later one from a junk yard and upgrade it, its cheaper than doing the earlier ones. just my 2 cents

okay I didnt read the whole thing there so you already have the better trans cause if you didnt I am sure the shop would have said so!!!

I like my lock up and I've got no tach but it sure sounds and feels like more than a 300 RPM difference. I flip the switch and it acts just like dropping into another gear. I also think your're right about heat - locked up, no slippage, less shear heating of the oil.

http://www.chuckthetruck.com/Page26.html

I agree with chuck. Mine has a lockup & its like another gear. It drops about 6-700 RPM on my car & I think it probably does on the truck too. I shure wouldn,t let them put in a high stall converter. They are a nusense to drive & only nessesary if you have a wild cam or going raceing.I used a vacuum switch off a late 80,s van & a pressure switch on the 4th gear test port & made the lockup automatic. You can run the lock up converter without locking up. I ran one about a year like that before I put a lock up system on it. I believe the good ones were the 87 & latter.

Yeah, I talked to the guy this morning, conveying my concerns about eliminating the lock up.
He claims he does this for all the local Vette guys and they love it. He replaces the entire valve body with one that no longer directs fluid to the now non existant lock up converter, so there is no danger of toasting the tranny. He is providing a 12 month/12,000 mile warranty. And said he would discount the cost of restoring the lockup if I really hate it. He does have an excellent reputation locally
He says since I am already running 3.08 rear end, and 31.5" tires. (I've been turning about 2900 rpm @ 70mph with the THM350, that gets me about 13 mpg in fuel economy department) that the 250-300 rpm difference(he insists that is the correct figure, I'll never know for certain)will be hardly noticeable and couldnt possibly result in any huge loss of fuel economy. Seems reasonable that with or without lock up I'll see a substantial decrease in fuel consumption, so I guess I'll be the guinea pig and see how it plays out.
He says the tranny will be ready to pick up by Thursday, but it will likely be around the first of May before I get time to install and take it back to him to dial in the TV cable. I want to have the heads gone thru, and install the new intake along with the tranny all at the same time, to see what impact all of it has on fuel economy. I'll add the serpentine belt system later, when the AC system is ready to go in. I'll post my thoughts on the tranny mods when I get it on the road first part of May. Thanks for your input.

you might look at this site:

http://www.700r4.com/tech/tc_article/index.shtml

http://www.bowtieoverdrives.com <- 2004r and 700r4 specialists

here are some other palces to poke around:

http://woogeroo.home.mindspring.com/autolinks/transmission.html

After doing some more reading, and talking to my buddy that has worked at Hydra Matic since '78, I went back and insisted that he not eliminate the lockup. Of course he conveniently already had the unit finished and ready to go. So he got me for an additional $185.00 to re programm again with a lock up valve body and converter, but I figure it's a small price to pay for peace of mind. Thanks again for the tips while I wrestled with this.