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the !#%** 700r4 question

boxer10

boxer10

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Hi all.
I am new here, got a long-winded tranny problem. I have a 1987 chevy cutaway (box truck) 1 ton, 350 engine, dually. The original transmission burned up and I had to buy a used tranny (funds were non-existent) to replace it with. I have very little knowledge of transmissions, and the shop did the replacement with a used 700r4 for $500. I tow a small enclosed trailer with my motorcycle in it, probably weigh's in at a little over 2000 lbs. 500 miles later, this tranny would no longer shift, so I had it rebuilt. After the rebuild, the shop owner said he is no longer in business and the overdrive in the transmission does not work- he said it's no problem because I should not tow in overdrive anyway. Yeah, I know, red flags all over the place. But the guy gave me a big discount. My wife and I are on SS, the only income we have. Anyway, now the tranny won't shift out of first unless I punch the accelorator to the floor real quick, and then it shifts. I do not have the resources to take care of a new rebuild myself(we are both disabled). My question is: Should I buy a new transmission from Jasper or the like, or should I have this 700r4 rebuilt by a reputable builder? And, since my indicator on the steering column says P R D 3 2 1, could it be possible that this is not even the original transmission that came with the truck? If not, is this 700r4 better than the original? whew! Please excuse my 20 questions!:(
 
did this place do the install or did they just rebuld. Also you should check the throtle postion cable make shur it's hooked up on both ends. Any way its a good trany. been around forever and there lots of upgrads to make im bullet prof.
 
It sounds like you are faced with either a rebuild or a replacement.

The 700R4 is probably original spec in your 1 ton. I had an '83 K20 with a 700R4, and never cared for it. The overdrive was nice on the highway, but it too had shifting problems similar to what you describe. The TV cable ended up being the cuplrit.

Here is a link that might help you diagnose the problem, if in fact it is the TV cable. http://www.cpttransmission.com/tech_tvcable.htm

In answer to your "rebuild or replace" question, a lot has to do with whether you have a reputable tranny shop in your area.


BTW, that steering column display that you describe is the same that my K20 had.
 
Boxer, often the TH700R4 suffers from TV issues.. TV=throttle valve. This 'valve' is located in the 'valve body' and is connected to the throttle pedal/linkage via a cable. This cable is adjustable. It must be hooked up to your throttle body throttle lever. (you might have a carb, same basic deal). Sometimes this valve gets 'stuck'.. One of two things must then happen: 1. Disconnect said cable at carb/TB engine idling, pull and retract this cable several times QUICKLY to try and loosen up the 'trash' in it, OR drop the pan, R+R the throttle valve to clean it the hard way...

If the cable is left disconnected, the factory default has it configured to max out line pressure, which can cause your late (harsh) shifts... Or it could be the dirt/trash deal above.

Very sensitive little valve, it is.

How to adjust: Depress the lock tab on the cable.(half-round tab) Move the slider rearward fully. Then fully open (engine off) throttle to ratchet the the cable adjuster forward. Done. One can fine tune the shifts a few clicks either way to suit application.

I can rule out a governor problem, since it will actually shift out of 1st gear.. (the part with the green gear)

Other pic is a TV valve disassembled

Other pic is what the TV cable looks like connected, and the half round tab you depress to adjust.

Hope you can get rollin'.

DSC00041.jpgDSC00057.jpg

attachment.php
 
Gerrysjeep:
did this place do the install or did they just rebuld?
They did both. Had a couple of helpers that knocked the spark plug wires off, I had to find it and point it out to them
3500GMC:
I will remove the doghouse cover today and check the cable. It is TBI, by the way.
BudTx:
I will be doing long distance driving, we live in the truck. I am to the point where I don't trust any transmission shop. I know there are reputable builders out there, but I need to find one that I can stand over.
Thanks everyone for your suggestions, I will proceed with it today.
 
OK, guys, I pulled the doghouse cover and attempted to adjust the TV cable. Only problem is, I see absolutely no way to adjust it. Behind the bracket that holds the TV cable in place is a metal shroud that has no tab. tv cable 001 copy.jpgtv cable 002 copy.jpgtv cable 005 copy.jpg
 
Top one is throttle, bottom is TV. No tab or slider??

added: your finger is on the throttle cable in first pic.
 
First pic shows arrow pointing to the metal enclosure on the back of the tv cable bracket. No adjustment tab anywhere. Third pic shows a blurry image of the metal enclosure behind the bracket.
 
Ok I see now, that 'should' be it. The tab is probably pointing toward the engine. They are adjustable. You should see a tab or at least a 'place' that you squeeze to let the slider rachet forward and backward. You can release the cable from the bracket to see it better. Before you do that, start the engine in park, un clip the cable from the throttle lever and give it a pull by hand.. There should be a progressivly harder 'spring' feel as you pull.


This is a pic of one for a G2500 from rockauto:
getimage.php
 
yeah, i want to know also.
i had an 81 with manual and was told 82 was the first year for the 700R. at the time i wished i had one. i ended up with a TH350 in it when i finished.
also had an 89 1 ton, square body, that i put a 700R in and it was a beast. had it beefed up with Corvette serve. sold it and the guy would pull way beyond the limits of the design but it never missed a beat. i also had a carbed 4.3 in it.
 
3500GMC said:
Well?
Click to expand...

Sorry for the late post. There has been a lot going on with my disabled wife. I decided not to get the 700 rebuilt (cost) and I never could get the cable right. I am getting a built th400 put in. There might be a couple of problems with installation, but my mechanic can handle it. What a difference in the planetary gears! The 400's are huge, the 700 is a little dinky thing. I also went with the 400 because I can watch every thing the mechanic does, since he is letting us stay on his lot.
 
deejaaa said:
you are gonna miss that OD.
Click to expand...
Very much so you are going to loose 5-6 mpg and if you did change the gears up to something suitable for a direct drive transmission you would still be down 3-2 mpg. Bad idea. A 4L80E would be the ideal choice, a TH400 with 4 gears, but its a bit spendy. I wouldn't trust a shop that couldn't adjust a TV cable with jack IMHO.
 
Yeah, I thought long and hard about it. It's a return to the old school. I don't have the funds for a "built" 700. I could get a 400 much cheaper, and it's already been torn down and built extra HD. We are parked in near Gatesville, on the mechanic's lot. That was a bonus for us also, otherwise we would have to pay rent at an RV lot until we had the funds to do the tranny. Next step is to try to get some cheap brakes on the trailer.
 
Before ok-ing the swap, you may have your Mech drop the 700's VB and clean it out- it's not all that hard and can be done trans 'in'... If your fluid is still red and unburnt, the VB could be the whole issue. All it takes is a spec of dirt, hair, fuzz to stick a valve.



Either way, best of luck.
 
Good idea. 3500gmc
You can also buy a NIB valve body off ebay for about 150$ and also use a sunnax ream and sleeve kits on those valves in the front of the trans that wear out their bores. Then the trans is just like new from a control standpoint. for maybe 300$ in parts. I have one here that got red necked at some point and shifts all messed up, its getting this treatment to unscrew it. Usually weird shifting issues can be traced to leakage in the hydraulic circuit, in this case the aluminum bores of the valves that shuttle a lot (like the TV) wear their bores out and are suspect. I wish GM had put all the high cycling valves in the cast steel valve body.
 
All TH700R4's have cast iron VB's.. The 85-ups have the Aux VB's that are Al..

Bore wear is not unheard of.. But rare- if worn it's usually in the TV and TCC apply bores.. Usually the spool valves themselves get rough and stick first.

TransGo has a nice Throttle Valve that is made for the worn TV bore.. Works as advertised.

The 4L60-E however... Aluminum VB...?! You gotta be kiddin me... :rolleyes5:
 
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