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for you guys with a 700r4...

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reece13

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Well, got a question about these 700r4s to any of u who know much about em. Ive got an 89 k5, 350, 241, 700r4. currently running 37" tire. Im in the process of an axle swap as we speak, so currently i only have a 3.73 gear (going to 4.56s), BUT i dont use OD unless im over 55mph right now since my ratio is numerically too low. I cruise around town just in D. I went on a short trip (3 hours 1 way and 3 hours back) about a month or so ago that was all hwy driving and ever since then my shifts have been wierd. The shifts are consistent every day, but i always seem to get a real soft shift from 2nd to 3rd.(and no, its just not in my head) Everything else works as it should with the tranny (such as lockup, reverse, OD, etc). This is def. worrying me though since the tranny has around 160k on it. The filter/fluid has always been changed about every year or 2 and i actually just changed it about a week ago and the fluid looked great and wasnt low...

Is there something im missing???? I dont mess with the TV cable so it should be where its supposed to be...any suggestions???????thanx
 
I would try to reset the tv cable. A little tighter will not hurt it. Too loose is what kills them. And thats info straight from my tranny guy thats been building 700r4s for over 30 years. So i trust his info over peoples opinions. :waytogo:
 
yeah, push the housing towards the firewall while pushing the "D" shaped button, do only 1/16" or one click. Try it and see if it helps. It wont hurt anything to try one or two clicks. If it doesn't get any better, just put it back where it was so you keep your "beginning". Also, and I know you are in the middle of an axle swap, I would go 4.88s with 37" tires and use OD. I have a tranny temp gauge and can see it running cooler in OD.

calculator
http://www.grimmjeeper.com/gears.html
 
K85 Octane said:
yeah, push the housing towards the firewall while pushing the "D" shaped button, do only 1/16" or one click. Try it and see if it helps. It wont hurt anything to try one or two clicks. If it doesn't get any better, just put it back where it was so you keep your "beginning". Also, and I know you are in the middle of an axle swap, I would go 4.88s with 37" tires and use OD. I have a tranny temp gauge and can see it running cooler in OD.

calculator
http://www.grimmjeeper.com/gears.html
Click to expand...
X2 on the gearing. I ran low 2000's (wanna say 2200) RPM with same tire size and 4.88's. bad ass combo right thur!
 
Could have possibly damaged the clutches or seals that seal up the 2nd gear and control the 2-3 shift. If/When it goes out, have them update the tranny with the newer pump, the corvette servo never hurts, and a new sunshell. They are not a bad tranny, and most people that tear 4 or 5 of them up is incompetent. They are not a 4L80E, but they can take quite a bit of abuse if the TV is adjusted correctly and the fluid is kept cool.
 
My buddy just got his rebuilt and put the transgo stage 3 reprogramming kit with corvette servo and all the other goodies, and holy crap does it shift AWESOME. 1-2 puts you in the seat and it just gets it. Mine has the stage 2 and its really crisp firm shifts. But stage 3 is way more funnerer :D And going from a th400 to the 700 the truck is sooo much quicker and the rpms are so much lower at cruising.
 
I agree w/ octane and doon. go to 4.88s if you're running 37s. i also have an '89 w/ same drive train but on 35s w/ 4.56s. it's perfect w/ that combo. i run about 1950-2000 rpm at 55-60 mph and it holds the gear/ OD, no more hunting. if you're going up one more tire size, go down one more set in gears.
 
I agree with everyone else on the 4.88 gears and that you should adjust the tv cable as tight as it can possibly be at wide open throttle. This trans does not have a very firm shift from 2-3 to begin with in stock form but can certainly be improved during a rebuild as others have noted, I am keeping mine for my big block swap.
 
Greg, I was curious as to the bracket you are going to use. Do they make one or are you makin it yourself? I could use the 700s lower gear and the OD, but wasn't aware of anyone making a tv bracket for a BB
 
454Sub said:
Greg, I was curious as to the bracket you are going to use. Do they make one or are you makin it yourself? I could use the 700s lower gear and the OD, but wasn't aware of anyone making a tv bracket for a BB
Click to expand...

I don't want to hijack the thread, but since you asked, I will be using the small block throttle body arm and welding it to the big block throttle body. I will drill a hole through the throttle cable bracket and use a Lokar cable that double nuts or hack a small block bracket for a stock style cable and frankenstien my own version out of both. I have done it both ways and it works very well.
 
Greg, not sure if this is a hijack, since its close in line with what the op was asking. I was not going to bother posting this yet until I had more info.

Friend of mine has a 2005, 350 engine, and I assume a 700R4. He is religious about pressing the towing button to lock out the overdrive when he tows something.

He says lately when he approaches a hill, the truck seems to slam down a gear and the engine revs much higher than it used to.

Says it used to just take some more throttle and it would power up. Now it downshifts.

Unfortunately he is about as non mechanically inclined as anyone you will ever meet.
So, until I get to drive or at least ride in the truck, I can't depend on what he is saying.

But, it sounds to me like the transmission is downshifting in places it did not used to.

I kinda suspect its an engine problem instead of the tranny, but how does that transmission know when a downshift is needed?

I know on the older transmissions the vacuum modulator signaled when the engine was loaded.
Does the ECU or whatever controls the shifting have a vacuum reference?

I just remembered he also mentioned a day or so later that his gas mileage has gone way down.

I think I see a pattern...........
 
454Sub said:
An 05 has no vac reference, as its a 4L60E. But the 700 didn't either. A th400 does though.
Click to expand...


I knew the transmission didn't since its electronically controlled. But I was wondering how the controller knew when the engine was loaded and a downshift was needed.
I figured there might be a vacuum reference that the controller read.

Otherwise I guess its a combination of throttle position sensor position and rpm.
 
454Sub said:
An 05 has no vac reference, as its a 4L60E. But the 700 didn't either. A th400 does though.
Click to expand...

This,...plus I would suggest your friend replace his fuel filter, clean his MAF sensor and see if he doesn't get some power back. If not, check for exhaust restriction or low fuel pressure. The modern computer controlled automatic is a slave to the ECM/PCM and only does as it is told.
 
Well the PCM runs the show and it already has a MAP sensor and TPS so why would the tranny need a vac reference or TV?

There was no 700R-4 after the early 90's when it became 4L60E, and there are some other variations. Anything with a tow/haul button is electronically controlled.

As for the original question, the 2-3 shift is the toughest one in a 700 because one clutch is releasing (2-4 band) while another engages (3-4 clutch), so the timing is important. A change could be from any of the following:
-line pressure is reduced (TV, bad filter?)
-Worn 3-4 clutch or leaking seal on apply piston/valve (clutch coming in slow)
-TV adjustment has changed
-reduced pressure to servo or leak (band releases early)
-sticking valve
-broken accumulator spring

How to fix it? The easiest thing is to pull the TV adjuster back 1 click and see if that does it. A bigger servo would firm up the 1-2 shift, but bigger is also slower, so it would make the 2-3 even slower, maybe even flaring up. The accumulators are relatively easy to make changes to and a basic shift kit might make the 3-4 clutch come in harder. You'd have to look into the details of this. If you make that too fast the tranny will bind in the 2-3 shift.
 
Well there was 1 thing i left out when i originally posted this...the slow 2nd to 3rd shifts only happen after ive been driving the truck for about 5-10 minutes. In the morning, it shifts like "i think it should" (obviously its a colder shift). It shifts "soft" after it seems to have warmed up a bit and continues to shift that way the rest of the time i am driving it. Could it be a bad valve body or somethin?? I will try the tv adjustment by 1 click in the morning, maybe that is the problem.....:dunno:
 
Hey just for $hits n giggles check the tcase fluid level. When my input seal on the tcase went bad it leaked tranny fluid into it and the shifts got soft... If your tcase is really full then the front seal is bad...
 
Alright, I just went and looked at a truck and the TV cable was broken, I can't remember anymore but will it lose reverse? It has forward gears but we didn't drive it, buddy of mine just bought it and we looked at it tonight
 
Dude, if its an actual TV cable, and not a kickdown cable on an older transmission, DO NOT drive it.
Not even a little.
You can burn it up in just a few miles.

The TV cable is what increases the pressure when you first start to give it gas. Until then, the hydraulic pressure is kept very low at idle. I imagine for gas saving.

If the pressure is not increased by the cable, the clutches and brakes will not apply full force and can slip and burn up.
 
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