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Discussion Starter #1
I have a 1991 Chevy 305 half-ton 2wd gas pickup with a bad transmission.

I was wondering how many years back I can go to find a 700r4 transmission as a bolt-on replacement.

Does anyone know?
 

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Discussion Starter #4
Yeah, my truck has the original 700r4 in it now (without 3rd and 4th gear...heh heh).

So I was just wondering if all 2wd 700r4's are the same, or what modifications or adaptors I will need if I go too far back (or forward) in time.
 

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The 700R4 was used for a relatively short period of time, so I do not think it is an issue. I know the engine block casting changed in '87, but I am not sure it changed the transmission mounting. You definitely need to find a 2WD one, though.
 

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Discussion Starter #6
I found a "700r4" in the local shopper newspaper for $50.00

The guy said he was going to put it in an '86 Caprice that he no longer has. He said it came out of a Suburban. I asked what year Suburban, and he didn't know...he only knew that it was for a 2wd vehicle.

So, that's where I am at. I figure for $50.00, it's worth attempting the swap as-is and seeing what happens.

Anyone have any advice? Will it work? Is there a way for me to figure out what I have in my hands after I pick it up? Markings on the transmission maybe?
 

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When you get it in you must bring it to a tranny shop and have them set/adjust the tv cable. If it's not adjusted right you could burn it up faster than you put it in. I had an article here on how to do it yourself but I lost it. If I remember right, you need a pressure gauge and adjust the cable so it gets pressure the moment you touch the gas pedal. I'm sure someone here knows more about this than I do.
 

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I would have it checked out first ,have put in to many so called ready to go tranny's then have to pull them out
 

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Discussion Starter #9
Thanks for the input guys, I am going to check with a tranny shop and see what they'll charge to look it over.

The tranny has all of the cables and hoses still connected but clipped off at about 1 foot, so I am assuming that this tranny came directly out of the original vehicle. (If it had been rebuilt, then the cables and hoses would have been disconnected, not clipped.) Now I'm just hoping that the reason it was removed was because the engine was hatched...not becuase the tranny was bad.

For my application, I think it will be worth it to install and pray. All I need is a wood-hauler truck. I paid $1300 for the truck, and I don't have it in my budget to make it a $2000 truck. If it doesn't work with this tranny, I'll sell the truck with the a bad tranny and find a replacement truck for whatever I can get for this one.

Still curious if anyone knows how I can identify whay year tranny this is. Are there any markings that may tell me?
 

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Discussion Starter #10
I found out how to identify it:

http://p210.ezboard.com/f7387chevytrucks88686frm2.showMessage?topicID=1067.topic
 

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Originally posted by RXL95
[br]If you don't need overdrive turbo 400 way better option will run forever
Yes, TH400s are awesome, but then he would probably have to find a different driveshaft. TH400s have no detent cable. I am not sure how that would work putting it into a vehicle that didn't previously have the 400.
 

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Discussion Starter #13
Well, it turns out I got an "early" unit. The 700r4 I got is stamped as an 1984 model, and the torque converter from my 1991 was NOT interchangable...just as someone else warned me about. (The the transmission's shaft has 27 splines instead of 30.)

So, I had a friend stop in at the local "Advanced Auto Parts" store, and according to the guy there, they don't believe that simply ordering a 1984 torque converter (with 27 splines) will work because they said that it will not bolt up to the 1991 the flex plate. And on top of that, they also said that swapping out the flex plate will not help either because the "button" on the torque converter will not fit into the crank on the engine.

Does this all sound correct? Or is there a custom torque converter out there that someone builds that will fit? Or do I have any other options (other than changing the shaft in the transmission)?
 

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Discussion Starter #14
Well, as it turns out, I THINK the guy at the auto parts store was wrong.

I am going to go ahead and order an "early" 1984 700r4 27-spline torque converter and give it a shot. From what I've heard from other experts, the 1984 700r4 27-spline converter bolt pattern and "button" will fit in my 1991 with no problems. I'll keep y'all updated.
 

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Originally posted by JD
[br]
Originally posted by RXL95
[br]If you don't need overdrive turbo 400 way better option will run forever
Yes, TH400s are awesome, but then he would probably have to find a different driveshaft. TH400s have no detent cable. I am not sure how that would work putting it into a vehicle that didn't previously have the 400.
Simple wiring to the tranny.
 

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Simple wiring for the transmission. Okay, point taken. But what about for the computer? I wonder how it would affect it.

If going with a TH400, he will probably run into the same problem as with the early 700R4. Unless he found a '87 or later TH400, which is fairly rare.
 

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Discussion Starter #17
UPDATE:

Sorry for not responding to your TH400 comments, but I already have the 700r4 that I picked up for $50, and I was focused on giving it a try before moving on to any other major transmission model change swaps.

However, no matter anymore...I have great news!

The 27 spline torque converter fit perfectly onto the transmission, and onto the flexplate, and into the crank.

I swapped the transmission tailsections to make the speedometer swap easier. I ended up having to melt the brazing that was holding the metal speedometer gear onto the output shaft, and re-braze it onto the other transmission since they were different styles. (One was plastic, one was metal.)

All things considered, the swap went perfectly. Everything was completely interchangeable.

And guess what ???
THE $50.00 1984 TRANSMISSION WORKED WITH NO REBUILD!!!
This absoluely blew my mind. I thought for sure I'd be pulling it out and rebuilding it.

Not only did I get my 3rd and 4th gears back, but it will actually drive in 4th gear at 40-45 mph. Never had that happen in 4,000 miles of driving with the old tranny. Before, I could only occasionally get it into 4th gear, and I had to really get it up to speed before it would go. That is, if it would go.

Now, onto the supposedly highly important "TV cable" adjustment. I have questions.

I left the same cable that was on the 91 truck on there, I didn't swap it out. After hooking it up to the 84 transmission, I then hooked it up top. I decided to just leave the slider right where it was...without "pressing the release button" on the adjuster. When at full throttle position, I checked the exposed metal cable by pressing on it, and there wasn't any obvious extra cable slack to be pulled. This is how I've ran the transmission so far, and when on the road during the initial tests, the shifting and downshifting "feels right".

So, my question is, if everything is shifting and downshifting at what "feels to be" the right places, is everything ok? Or what mandatory things should I check for so I don't ruin the transmission? Does anyone recommend "pressing that adjuster button" and setting it (by opening the throttle all the way) to "set" it properly? Or is that not necessary if it's currently running right?

Another rumor I've heard is that it is better to have the TV cable to tight than too loose to be "safe". What exactly will an adjuster setting of too tight "feel like" when driving the truck during downshifts? (Or what will too loose "feel like"?)

Am I just paranoid about the TV cable?
 

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Congrats on the successful job. It's always nice to hear when tranny swaps work out. I've had my share of swaps that resulted in finding a different tranny because the one I bought was suppose to be good.

As far as the TV cable goes, from what I've learned from my local tranny shop is that on a 700r4 that cable controls pump pressure. There is suppose to be a certain amount of pressure the instant the throttle is touched. When I had a 700r4 rebuilt(carry in) they made it very clear that I drive the truck straight to them so they could adjust the cable or my warranty would be void.

If I were you I would at least call a tranny shop and ask them what they think. It is possible that I/they are full of it. But it's best just to make sure.
 

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we put a Turbo 400 in a buddys 2wd truck.. it had a 700r4.. well 6 of them... hast had a prob w/ the 400 yet.. all he needs is a speedocable and had to get a driveshaft made...
 

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The adjustment to the TV cable is very simple, anyone can do it.
Locate the button on the top side, push down on it and hold it down. Then while holding the button down slide the plastic part of the cable back into the cable housing (toward the firewall) and release the button. Now all you have to do is open the throttle wide open and you will hear a ratcheting sound. That sound is the plastic part you pushed back into the cable housing coming out and self adjusting. Now your adjustment is complete. Put the air cleaner cover back on (if you even had to remove it) & take it for a test drive. If it upshifts correctly and down shifts correctly, you are done. Sometimes these cables get stretched out over a period of time and mileage, so you may need to push the button down and push it in or pull it out just a little bit from your self adjustment point. I think they are only like around $20.00 for a new TV cable from the dealer. Hope this helps you out--good luck!

Oh yeah--in the future, any time you have shifting problems w/ a 700R4 always check that TV cable first. I have bought a lot of S-10' and full size trucks from someone who thought the tranny was junk; only to get it home and look over the TV cable and find it broke (or not in the bracket correctly)-not hooked up-or just out of adjustment or stretched out and needed some fine adjustment (in or out. Sometimes they come disconnected at the transmission also.
 
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