stangStomper83

im shopping for a new tranny (700r4) whats the difference between lock up and non lock up. can i use either one and what are the pros and cons. any help would be great thanks.

Apeiron

Locking torque converters have a clutch to eliminate slippage while cruising for reduced heat and slightly improved mileage.

greggbruce

iTrader: (1)

ALL 700-r4's (4L60) are lock up. all 4L60e's are lock up.
some 350's are, some 200's are, and all 2004r's are.

to make things easiest, get the same thing you got now, if you need a new one.

87zjeff

iTrader: (4)

700r4's can be modified to use a non-lock-up convertor. some companies build them like that.

greggbruce

iTrader: (1)

true, but for racing applications. like 1/4 mile at a time. the 700 was designed to have lock up in at least 4th gear(3rd and 2nd too), which is to keep the converter from slipping and heating the fluid. mind you, that is not the ONLY reason, I believe it was for fuel mileage to start with. if you make a 700 non-lock up, you run the risk of overheating the fluid on long trips, and smoking the trans.

but yes, they are available(the torque converters) and there are some modifications necessary internal to the trans to make them work, too, but GM never made a non-lockup 700.

onfire

Just for some clarification....
when you say that all 700-r4's are lock ups is that also true if you are at wot? i ask because my 700r4 does not shift into the "4th" gear at wot but when i lift my foot off the accel just a bit of off wot it likes to shift into that last overdrive gear then any more it wants to kick back down and we do the dance till either ive had enough or it doesnt go much faster so it could be a governor but of what ive been told is that its the torque converter being a non lock up which doesnt lock in that 4th overdrive gear into place... any clarification is appreciated or should i post this in its own thread ....??

Apeiron

The ECM will unlock the TCC at WOT, but the 700R4 also won't shift into O/D at WOT.

greggbruce

iTrader: (1)

lock up or non-lock up denotes what kind of converter it has.
WOT, yes, the computer disables lockup, but also the high pressure from the tv cable also keeps 4th gear from happening. but that doesn't mean the trans is no longer a "lock up" trans. it just means it's NOT locked up.
there are kits to replace some valves to prevent this from happening, and seperator plates, too.

I never had this problem with my 87 350 formula. I think I was lucky. I never had to fix it for that problem. with my 406 motor and 3.27 rear end gears, I've had it past the 140 mph mark a few times, and it would always hit 4th, somewhere around 115mph.

do some online searching for the valves, I forget who makes them.
you might try sonnax. they make a lot of trans "fix it" parts.

I can do some checking too.

87zjeff

iTrader: (4)

transgo makes a kit, B&M makes a kit, and GM has the factorsy version that came in vettes, irocs, and some firebirds.

onfire

i heard that the 700r4s dont have a 4th gear its an overdriven 3rd gear so it wouldnt handle the power as well as a th350 or th400
so would it be worth it to put these kits in to lock the last gear in at wot?
my setup takes me to 130 mph .... well anyhow just curious ... what would you guys think a relatively built 700 can handle in terms of hp and torque.... it has been built by a factory "professional" do for all thats worth !! lookin to get a new cam and dont want to over do it... any feed back would be nice and hope we're not strayin away from the origional topic tooo much

Apeiron

Those kits have nothing to do with locking the clutch, they're for letting the transmission shift into overdrive at WOT.

I don't know what you mean by an "overdriven 3rd gear", but the 700R4 is a 4 speed tranmission with overdrive. The fourth gear is the overdrive gear.

Ozz1967

iTrader: (4)

So a stock 700R4 will never shift into OD at WOT? Currently, it seems that if I have the throttle more than 75% of the way down, it won't shift from 3rd to 4th. I would love for it to be able to drop into over-drive with my foot on it all the way! Is it possible to do that or not?

Apeiron

Why would you want to?

Ozz1967

iTrader: (4)

Oh, I don't know. Maybe when I get shipped to Germany next summer as my orders say then at WOT I can keep going faster? In 3rd gear I'll tach out though because my speedo only hits 85, I don't know how fast I'm going. Somewhere in the 115 range I'd guess right now. If I could catch over-drive when I'm in 3rd gear at say 5500 rpm, then well...I'd have at least another 500-1000 RPM to play with. Probably hit 140 or so that way. But other than that, no particular reason.

86iroczz

I think of a 700r4 as a double powerglide. Actually has clutches for 1-2 shift and 3-4 shift. A band is used from 2-3. Its much more like two 2 speeds that a three speed with a gear added.

ANY kit or valve body made by anyone that gives you 4 independent gears as if you have a stick shift, will make it so you can shift and go wide open throttle in any gear you wish. Check it out and get rid of the TV cable while you're at it. Of course, at that point the "automatic" doesnt apply. But I believe its the best way to drive these things and stop the nonsense. Just shift as if it were a stick and dont use that clutch, its really the brake .

Lockup is a waste and not needed on any part time race car; asking for yet another thing to go wrong. When I think of the 5 dollar brake activated switch that turns it off I get completely disgusted with a 1400 dollar transmission. If you can find the proper modifications to remove it and buy a nonlockup higher stall converter, by all means do it.

Yes certain years are more prone to overheating when lockup is removed. So add it up, 5 dollar switch on brake goes out and fries tranny. At least the cruise control has a second off switch. Great engineering. Add a cooling pan and a tranny cooler at the radiator and call it a day.