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focking 700r4s

black rust

black rust

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First I lose reverse in the trans in my k5. So I go to the PNP and pull a different one, courtesy of an 88 suburban. When I go to pull the pan off, I find this.
DSC02292.jpg

So I figure I can just pull the part off of the other broken trans I pulled from the blazer, since the fact that forward gears still worked and the black crap in the pan leads me to believe the problem wasn't in the valvebody. When I pull the pan off that one, I find something different.
DSC02291.jpg

I would prefer not to go back to the JY and spend another saturday pulling another trans. Plus I won't be able to get back there for two weeks, and I know its going to get a lot colder real soon, which will make it even less fun.
So does anybody know if I can combine parts to make a working trans out of these two?

Or did I do something really stupid and not pull a 700r4? (Even though the cases look identical
 
'88 and '85 are essentially the same transmission (in regards to having only TCC being electrically controlled) but in '87 there was a major redesign which changed the valve body and a bunch of the components to include the case itself. Didn't change it externally (much) but internally quite a bit, which is when the reputation for the 700 started to change more favorably.

The '88 case should have a half circle cast into the passenger side, part of it passing right through the cooling line fitting taps. This indicates the later redesigned case/interals.

Can't answer specifically what if anything else internally is not interchangeable, but even a minute change in a piece could be disastrous trying to mix and match between years.
 
So I'm pretty much gonna have to get a different trans? Any idea what that part is in the first pic or how much it would be to replace?
 
I'll respond solely because no one else did to try and answer your questions. (and that this thread was just linked to:)) I'm surprised we don't have some auto transmission experts that chimed in!

Anyways, the only way to REALLY know if the parts could interchange is to pull the valve body off, and anything else that is different, and see if the passageways and what not are the same.

Personally I wouldn't waste my time, I'd be willing to bet that just about everything related to the valve body is different, and probably some other stuff that isn't visible from a cursory teardown. 700's are finicky enough as-is, "blindly" trying to mix and match parts is certainly asking for problems.

I suppose the JY won't give you your money back, your only recourse is to get another transmission? I'd stick with the later model 700's, the newer you get, the more refined it's going to be. Of course, you might end up with some TCC wiring differences, but those can likely be rectified. I'd compare the way the two you have now are wired, as one will be ECM controlled TCC (the '88) the other will be vacuum switched. If both are wired identically, then there is likely no problem using a 700/4L60 up until they changed to the 4L60E. (no TV cable)

Or, get a manual transmission and be done with all this silliness. :)
 
If I was in that situation, I would try to run the later model tranny by replacing the auxiliary valve body. Check with local tranny shops, they may have some parts trannies laying around that you can get the broken aux body from. That part is supposed to ease the shock load of dropping the transmission into gear. It is entirely possible that you can put a block off plate in it's place and run without it. The older ones had a plate that bolted in back there (you can see it in your pictures), which I was always curious about. Why have features in place for a part that hasn't been in service yet? It's likely the introduction of the aux valve body was delayed for a few years or that it only went into cars.
 
I could take the trans back to the JY I pulled it from, and get a different one, but I would have to pull it myself and I won't be able to do that for a few weeks.

I'm not much of a tranny expert, so if i did manage to get a different valvebody, how hard is that to change out?

If I was going to keep this truck, I prefer to swap in a manual, but since I am trying to sell it, I just want to get it back together and out of my barn.
 
As I posted in the other thread, I'll see what the parts manual says (if anything) about the cases being different, or not.

Pure speculation, but perhaps GM foresaw the coming of more powerful motors (thats a stretch since they designed these probably in the late 70's, probably more likely that they anticipated using big cubic inch motors longer and instead saw mainly diminished engine size/power for quite a few years) and left room for improvement, or knew what they would need eventually. I would think that in R&D these things would come up, something fails at 100HP, you upgrade it, it doesn't fail anymore, if you increase the power, it's likely that same piece will need to be upgraded further, or worked around. I dunno.
 
I tried a valve-body swap once, from same year transmissions, and I couldn't get it to shift outta first.

I eventually found a stuck piston in the original, got it moving again, and it shifted after that. Still slipped a whole bunch on every shift though :( I put probally 10 000 miles on it that way until the engine blew and I scrapped the truck.
 
I would not try swapping the MAIN valve body between different year transmissions. The AUX body can probably be done. All you really need is the AUX body housing. You can swap the guts over into a different one. If it took any more than that, you're best off returning it. If the tranny doesn't work right is it your fault or theirs?

An 88 should be a good improvment over an 85

Near me there is a shop with like 1000 sq. ft of shelves holding old transmissions and parts. They have sold me sprags, a governor, speedo gears, etc. A few phone calls can probably tell you what shops sell parts to the public.
 
Would the auxiliary valve body going out like that damage anything else in the trans? I would be really pissed if I do fix this thing only to find out there are more problems with this thing?
I also looked at that site for parts, not quite sure where to look so I can't seem to find the auxiliary valvebody
Thanks for all the help
 
According to the '85-88 parts manual, there are at least 6 differences in the valve body assembly, all these are obviously between the aux valve body model and ones without. I stopped counting all the annotated differences.

For general knowledge, going to throw some other info in here as I browse the pages of the manual.

There were 5 different pumps used. 7 different input shafts. There are 3 different cases, one annotated difference is the auxillary valve body.
 
I've been calling tranny shops around here and everyone I've talked to thinks I'm crazy. Any specific places that should have what I want?
 
i've dealt with a plac called 'multistate transmission'. they were honest and knew their stuff. they mostly do rebuilds and repairs, but they'll sell some parts individually, too. they rebuilt my daily driver 4L60e with 'vette parts (big improvement) and 2 of my dad's cars have had trannies from them. his honda tranny just passed 30K miles and the taurus' tranny had over 80K when he sold the car. no problems.
 
Local place I know of that stocks used parts is where the local GM places send their transmission work. You might ask a local GM dealership for that info, if they'll give it up and don't do it in house.
 
alright, I managed to get back to the JY today to try and pull another trans. Only one problem. They don't have any! I found only 1 4wd 700r4, and that one had the pan removed and part of the valvebody was missing. Does the 700r4 really suck that much that everyone has emptied them out of all the JYs around here? Damn, I am really pissed off right now
 
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