2004R

SS_Malibu

G-Body Guru
Sep 27, 2021
637
93
Mesa, AZ
I'm following along on this thread as I am planning a swap from a TH350 to either a 2004R or a 700R4. I'm not fully understanding the whole "Lock-up" thing with these transmissions. I think the 700R4 has a non lock up version as well, is that correct? And if someone could explain what lock up is for us who do not quite understand what that is and why it is relevant.
Thank You
 
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ELCAM

G-Body Guru
Jun 19, 2021
710
93
A lock up torque converter has a clutch disc in the front of the converter that can "lock" all the moving parts inside the torque converter and make the engine speed driving the torque converter the same as the speed of the gear inside driving the transmission input shaft.

A torque converter uses oil driven thru pitched vanes to multiply torque to aide in starting movement of the vehicle from a standing start. This design always has some slip and loss in it, The engine speed is always a little higher than the input shaft speed even when the vanes are angled at the least torque multiplying angle.

On a Lockup transmission the input shaft is hollow and there is a hole in the input shaft at the very front and there is an O ring to seal the pressure in front of the hole in the input shaft. When the electrical signal is applied a solenoid valve opens and allows oil pressure to go thru these passages and apply the clutch in the torque converter.

This allows the engine to turn a little slower (usually in the 3-400 RPM range) and be a little more efficient. This was an important improvement when the auto industry was trying to meet EPA fuel economy requirements with engines being the same old designs.

The first lock up torque converters were in late 1950s Allison truck transmissions. Chrysler was later credited with inventing it in the early 80s even though GM had done it a few years earlier and the design was Allison's.

All 700R4s are lockup designs.
 
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SS_Malibu

G-Body Guru
Sep 27, 2021
637
93
Mesa, AZ
So all 700R4's and 2004R's are lock up converters, correct? If you opt not to use the lock up feature then the only downside would be a little lees fuel efficiency? Or is it highly recommended to use the lock up for proper trans function? I have no computer or computer controlled stuff on my car. I kinda like it that way.
 

ELCAM

G-Body Guru
Jun 19, 2021
710
93
Correct it will have no effect on overall drivability if you choose not to use the lockup function. Only problem I can see is heat, the transmission cooler system was designed with the lock up in mind so a little more heat will be present without the lockup. Just use a bigger cooler and there is nothing to worry about.

Yes all 200-4R and 700R4 are lockup designs.

Edited to add: You do not need a computer to operate the lockup function early 3 speed automatic designs with lock up predate computers (also pick ups did not get computers till about 5 years after the cars and they too used the lock up transmissions.) I would copy the GM design for this and use the vacuum switch, climbing hills with the lockup engaged can cause overheating of the engine.
 
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Oct 14, 2008
8,254
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Melville,Saskatchewan
I think I need to double check the code on the rear end I got. I keep saying 2.42 for some reason but I don’t think 8.5 come with that high of a gear. 3.42 rings a bell. I got an external lockup kit like the one you are talking about too. it comes with a switch you can control from the dash. My car still has the computer controlled carb and my th250 has a 4 prong plug with 2 wires that run back up into the engine wiring harness. What does it control and if I don’t use on the new trans is going to mess things up? Or do I even need the external lock up kit because the computer will do it?

And now a days if you are not doing at least 70 on the freeway you get ran over lol
It should work the same as your TH250C. There are variations in the wiring, 2 wire vs 3 wire. Yeah, between the 2004R with a better first gear with slightly higher torque converter stall and what should be 3.42 gears, it should be really fun compared to what it is with no mileage loss.
 

CopperNick

Royal Smart Person
Supporting Member
Feb 20, 2018
2,241
113
Canada
LIkely you will need a search engine to track it down but I did recently post a brief how to on dealing with the TV cable. Getting the cable tension just exactly right is the hardest part and can take more than one try but it can be done. Locating the correct cable mounting bracket can also be something of a headache but they too can be scored if you are will to wander through fields of hulks and do some exploring.

The lock up provision comes as a default ability in factory 200 R4's and 700R4's. The electrical plug in found on the side of t-case is not to actuate it, it is actually to de-actuate it during braking. The lock up automatically resets itself when you accelerate again. There are pictures floating around that I took of what/where the factory switch for the lockup looks like/can be found.

As for there being no non lock up versions of the 700R4, we-ell, the factory didn't as far as I know but, if you go aftermarket then TCI offers a non-lockup version of the 700R4 under their part number TCI1060. They have it listed in the 2022 catalogue on page 143.

Nick
 
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Street Sweeper22

Greasemonkey
Thread starter
Nov 18, 2017
145
28
I believe that 8.5 out of a t-type should have 3.42 gears in it. I could be wrong so if anyone knows better please chime in. I did a 200-4r swap into my 84 olds. If you are still using the original computer that plug that goes to the transmission for lock up should work on the new transmission. I did not stay with the computer control so i got a lock up kit from TCI. It works just an extra step. Mine is behind a high revving tire shredding 403 lol. Good luck with your install and happy cruising.
Thank you for the reply and I’m jealous of your 403!
 
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Street Sweeper22

Greasemonkey
Thread starter
Nov 18, 2017
145
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It should work the same as your TH250C. There are variations in the wiring, 2 wire vs 3 wire. Yeah, between the 2004R with a better first gear with slightly higher torque converter stall and what should be 3.42 gears, it should be really fun compared to what it is with no mileage loss.
The plug on the side of my transmission is a square 4 prong with only 2 wires. I’m hoping I get better gas mileage out of it. Doing 70 on the freeway in a 3 speed is not good on gas lol
 
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stew86MCSS396

Apprentice
Aug 1, 2022
81
18
(808)
No expert by any means but did want to bring up after the critical TV-cable adjust, you should check line pressure with a gauge to make sure pressures are within spec per the FSM each gear at prescribed rpm. Problem is most of us including myself don't own a gauge. I'm just learning all this stuff as I'm trying educate myself to rebuild one. https://nastyz28.com/attachments/th200_4r-pressure-settings-png.47335/
 
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Street Sweeper22

Greasemonkey
Thread starter
Nov 18, 2017
145
28
No expert by any means but did want to bring up after the critical TV-cable adjust, you should check line pressure with a gauge to make sure pressures are within spec per the FSM each gear at prescribed rpm. Problem is most of us including myself don't own a gauge. I'm just learning all this stuff as I'm trying educate myself to rebuild one. https://nastyz28.com/attachments/th200_4r-pressure-settings-png.47335/
Do you have figure 24 and 74 for tap location?
 

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