The electrical connection from the drivers side of the th400 case is not needed when converting to a 700r4 correct? Just want to make sure I can get rid of it before I start yanking it out. Thanks!
700r4 conversion...do i need electrical connection from th400?
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rock7174
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You will need a hot wire with the 700r4, but it will need to be ignition hot with the key on and fused or from the fuse panel.
What is it for? I see a 4 wire plug facing straight up on the drivers side. Is this it? Don't see where else it would go?
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The 4 wire plug on the 700r4 transmission runs into the transmission.....it (basically) controls shift pressure and torque converter lock up.
You will need to buy a wire adapter kit to connect the transmission electrics onto your car.
You will need to buy a wire kit for inside the transmission as well. This kit will include a new pressure switch as well as a servo and the internal trans wire loom.
You will need to buy a brake light switch that has provisions for two functions.....I use Cadillac brake switches because they bolt right in and they have provisions for two electrical functions (brake lights and Cruise control).......the cruise control function will be used to control the torque converter.
The 700r4 has an electrical speedometer signal output which wont work with a mechanical speedo cable. If you want your speedo to work, you will need to swap the 700r4 tailshaft and housing for a short tailshaft unit from a TH350, yes the TH350 unit will bolt onto the 700r4.....no, your TH400 tail shaft wont work with the 700r4.
You ABSOLUTELY WITHOUT A DOUBT, you must buy the correct throttle linkage "kick down cable" for the 700r4. The geometry for the arc of the kickdown cable should be considered the most critical aspect of this trans swap.
Consider the flywheel to torque converter bolt spacing measurements.....the 700r4 transmission is built with metric measurements.....TH400's use SAE measurements.....you will need a 700r4 flywheel.
Depending on the tooth count of your current flywheel, you may need a starter. If your current flywheel is the smaller diameter unit, your starter will work with a 700r4 flywheel
I've never gone from TH400 to 700r4, but I have done TH350's to 700r4's. I don't know what the trans x-member bolt hole specs are for the TH400, but with the TH350 I would use an Energy Suspension transmission mount, cut away all the poly material and use the top plate portion of the mount only. I will weld two nuts onto the plate inline where the trans x-member bolts would go. I would then bolt the plate to the transmission as normal and pass two bolts up thru the x-member screwing them into the welded bolts. Doing this would drop the rear of the tranny a couple inches giving enough trans tunnel clearance for the bigger 700r4 transmission (68-72 Chevelle's).
You will need to buy a wire adapter kit to connect the transmission electrics onto your car.
You will need to buy a wire kit for inside the transmission as well. This kit will include a new pressure switch as well as a servo and the internal trans wire loom.
You will need to buy a brake light switch that has provisions for two functions.....I use Cadillac brake switches because they bolt right in and they have provisions for two electrical functions (brake lights and Cruise control).......the cruise control function will be used to control the torque converter.
The 700r4 has an electrical speedometer signal output which wont work with a mechanical speedo cable. If you want your speedo to work, you will need to swap the 700r4 tailshaft and housing for a short tailshaft unit from a TH350, yes the TH350 unit will bolt onto the 700r4.....no, your TH400 tail shaft wont work with the 700r4.
You ABSOLUTELY WITHOUT A DOUBT, you must buy the correct throttle linkage "kick down cable" for the 700r4. The geometry for the arc of the kickdown cable should be considered the most critical aspect of this trans swap.
Consider the flywheel to torque converter bolt spacing measurements.....the 700r4 transmission is built with metric measurements.....TH400's use SAE measurements.....you will need a 700r4 flywheel.
Depending on the tooth count of your current flywheel, you may need a starter. If your current flywheel is the smaller diameter unit, your starter will work with a 700r4 flywheel
I've never gone from TH400 to 700r4, but I have done TH350's to 700r4's. I don't know what the trans x-member bolt hole specs are for the TH400, but with the TH350 I would use an Energy Suspension transmission mount, cut away all the poly material and use the top plate portion of the mount only. I will weld two nuts onto the plate inline where the trans x-member bolts would go. I would then bolt the plate to the transmission as normal and pass two bolts up thru the x-member screwing them into the welded bolts. Doing this would drop the rear of the tranny a couple inches giving enough trans tunnel clearance for the bigger 700r4 transmission (68-72 Chevelle's).
Darn it! I was on a roll with this topic. Thanks for clarifying though.
I wonder why I was thinking all 700r4's had electric speedo control. There's a reason why I always go with TH350 tailshafts/housings. I'm going to have to dig thru my brain on this one.
I have it mounted. Can use stock cross member with newly drilled holes. Mechanical speedo. I have read that you don't have to use the converter lockup feature? Got the TV cable, linkage, etc. from a TCI conversion kit. Isn't there two types of 700r4's? One you have to use electrical connections for shifting, etc and a older version that you don't? I thought I had everything planned out, now I am confusing myself.
700r4's are non computer controlled......4L60E are the next newest evolution of that transmission and they (4L60E's) are computer controlled.
You can use the stock cross member with newly drilled holes......actually, I wouldn't drill holes in the cross member, I would rather set the cross member in place while bolted to the transmission and drill holes thru the frame.
You're on the right track....no need to be confused.
Yes, you can run the transmission without the torque converter lock-up activated....it wont harm anything except your overall highway gas mileage.
There is a reason why I don't use the 700r4 speedometer/tailshaft. I'm thinking hard about it.....something to do with the speedo gear ratio maybe. Like, you'd be driving along @ 40mph, but the dash speed would indicate 100mph.....something like that. And a QUALITY speedo gear reduction box is close to a hundred bucks.....I can get complete TH350 tail shafts all day long at the recycler for 20 bucks and the speed on the dash will be within a few mph of actual.
You ban add the torque converter lock-up kit at any time later on without having to pull the transmission out.
Good luck, no worries. You are on the right track.
You can use the stock cross member with newly drilled holes......actually, I wouldn't drill holes in the cross member, I would rather set the cross member in place while bolted to the transmission and drill holes thru the frame.
You're on the right track....no need to be confused.
Yes, you can run the transmission without the torque converter lock-up activated....it wont harm anything except your overall highway gas mileage.
There is a reason why I don't use the 700r4 speedometer/tailshaft. I'm thinking hard about it.....something to do with the speedo gear ratio maybe. Like, you'd be driving along @ 40mph, but the dash speed would indicate 100mph.....something like that. And a QUALITY speedo gear reduction box is close to a hundred bucks.....I can get complete TH350 tail shafts all day long at the recycler for 20 bucks and the speed on the dash will be within a few mph of actual.
You ban add the torque converter lock-up kit at any time later on without having to pull the transmission out.
Good luck, no worries. You are on the right track.
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It can be an issue depending on the rear gear. If running 2.73 - 3.55 speedometer gears are available. 3.73 rear gear with the largest gear available will still be off, close but off. The error depends on the size tire. after that the conversion as Tony described would be needed.
wheew....good to know thanks. I thought lockup was something I can add later. Its not used for much highway driving. Occasional 30-100 mile trips a couple times a year. I will most like add the lockup at a later date. Got my plate full with too many upgrades as it is. Is the th350 tailshaft interchangeable with no driveshaft mods? My custom driveshaft is already completed.
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I just switched from a TH400 to a 700R4. The only electric connection needed if to engage the lock pin the converter. Other than that, it's all mechanical, no computer needed. About the flywheel, I was able to reuse mine as it had two sets of holes with different bolt patterns. The floor on the passenger side needed to be "massaged" a little to get clearance for the servo. You need to install a TV cable to the carburetor but if you have a Holley carb, the holes in the carb lever is aleady there so it's just a matter of hooking it up and adjusting it. I had a B&M shifter and was able to reuse it and the only change was to remove a pin in the shifter's mechanism (per the instructions) to allow one more '"click" for the 4th gear (when shifted manually). The crossmember is the same, only moved back a few inches and 3 out of the 4 holes aligned with the holes in the frame so only needed to drill one. The driveshaft needed to be shortened 3".
That's about it. The swap is being done right now so I haven't driven the car yet but I should very soon.
Claude.
That's about it. The swap is being done right now so I haven't driven the car yet but I should very soon.
Claude.
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6,401 Posts
Better read this before you proceed.
http://www.purplesagetradingpost.com/sumner/techinfo/700R4p1.html
http://www.purplesagetradingpost.com/sumner/techinfo/700R4p1.html
I will clarify some items.
Many VSSs in the 700-R4 are simply speedometer gears driving a VSS.
If you find a VSS that is offset below the output shaft, it will be simple to convert to speedo gears with instaling a sleeve and gear, or some truck units will require the reluctor changed to a gear. Easy.
There's no tangible advantage to a 6" TH350 tailhousing. It has smaller speedo gears is all. In fact, the B-body / D-body 700-R4 tailhousing with cast-in mount lets you use the TH400 mount location without change. And, assuming your TH400 speedo gears are correct, count the teeth, copy with 700-R4 speedo gears and you're set, as the TH400 uses similar teeth count ranges.
3.73 gears and a 26" tire had 1:3 speedo gears. It was 15 drive, 45 driven and no ratio adapter in a 3.73 84 Camaro. If you run much shorter tires, or go to 4.10 gears, that's when you have to work a little harder.
Converter bolt pattern to the flexplate is either 10.75" (all passenger cars) or 11.50" (probably truck applications.) If you have a mis-match of your 700-R4 converter pattern to your flexplate, dual-pattern flexplates are available.
Absolutely get the TV cable correct from the start. I can say a Q-jet for TH350-C car has the exact same bellcrank hook-up and bracket as a 700-R4 car, but don't know what you have.
Many VSSs in the 700-R4 are simply speedometer gears driving a VSS.
If you find a VSS that is offset below the output shaft, it will be simple to convert to speedo gears with instaling a sleeve and gear, or some truck units will require the reluctor changed to a gear. Easy.
There's no tangible advantage to a 6" TH350 tailhousing. It has smaller speedo gears is all. In fact, the B-body / D-body 700-R4 tailhousing with cast-in mount lets you use the TH400 mount location without change. And, assuming your TH400 speedo gears are correct, count the teeth, copy with 700-R4 speedo gears and you're set, as the TH400 uses similar teeth count ranges.
3.73 gears and a 26" tire had 1:3 speedo gears. It was 15 drive, 45 driven and no ratio adapter in a 3.73 84 Camaro. If you run much shorter tires, or go to 4.10 gears, that's when you have to work a little harder.
Converter bolt pattern to the flexplate is either 10.75" (all passenger cars) or 11.50" (probably truck applications.) If you have a mis-match of your 700-R4 converter pattern to your flexplate, dual-pattern flexplates are available.
Absolutely get the TV cable correct from the start. I can say a Q-jet for TH350-C car has the exact same bellcrank hook-up and bracket as a 700-R4 car, but don't know what you have.
I have 26" tires and putting 3.73s in now. I'll have to check the TH400 speedo gear. I got a TCI kit to use with a holley double pumper that comes with brackets, etc. My flexplate is dual hole design, so I'm set there too! Just ordered a lock up kit. Thanks for the info!
Yes....if you already have the drive shaft built for the 700r4, it will still fit with the TH350 tail shaft installed on a 700r4.....but make sure you get the (most common) TH350 tail shaft with 27 splines The 700r4 has 27 splines.
The short 9" tail shaft length is the proper one to use. Not the long shaft common to pick up trucks. And not the shortest 6" shaft found in some cars.
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