Spooky3g

Just picked up my first 3rd gen a couple days ago. Wanting to figure out if the car actually has a built trans? Or if it's going or something inside needs replaced. Here's what's happening:
Accelerating slowly from a stop shifting out of first seems to take a minute if I let it rev up to 4kish it will shift into second roughly. If I accelerate slowly and sit at about 3k it will shift roughly as well. But if you go from a dead stop and accelerate hard it shifts like butter and kicks the tires out. Does this sound like built trans or an internal issue. Thanks. New to all of this carb/autotragic stuff.

Spooky3g

Also 2-3 is significantly less rough but still kicks a little. 3-4 is not barely noticeable

NoEmissions84TA

iTrader: (1)

First and easy to check is the TV cable adjustment.

Spooky3g

Where is this cable located? New this this stuff.
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Hawgtied

I had one years ago that had similar symptoms. One of the planetary gear sets had went out. I went ahead and had the whole thing rebuilt-no real choice in the matter. Hopefully yours is just a built tranny so you can enjoy it! please report back your findings

Irocjay85

I think Im having the same problem, I have an 85 iroc with a 700r4 tranny with 410 gears and I get a little bit of a whine from the tranny when accelerating, mine doesn't bang into second but it shifts fairly rough when it isn't warmed up. If I let it idle a while before I taker it out of the drive then it seem to be fine. Although after it warming up and driving down the road when I accelerate I can hear the tranny whining a little bitr almost like its low on fluid but it isn't, I have checked and double checked, were thinking maybe it is the tv cable possibly not mounted in the right place. My motor is a 350 with a lingenfelter short ram intake, the tv cable bracket looks like it may be a home made job from the builder but Im not positive. My father in law had read that the tv cable had to be down 1" and back 1/2" from the pivot on the throttle, can anyone confirm this to be true? and if so can you attach a pic for me to see?
Hope to hear back soon, also this is my first forum that I am apart of so if this issue doesn't make sense for this thread plz advise.
Cheers

duanejangula

hi: I have an 98 Iroc with 700r4 tranny, 350tpi.. Mine also shifts (should i say) fairly hard/firm from 1st to 2nd and also the other gears it's a very firm shift. I have not changed any trany fluid since i had it. I got this car last fall and worked on some other items. Now starting to think about the trany.

Any comments/suggestions etc would be greatly appreciated.
Thanks. Duane

Irocjay85

My father in law and I are checking the tv cable and tv cable brackets tonight, if there out of adjustment that will make it shift hard, I'm tearing my torque converter out and getting a rebuild done on it because of the whine in the tranny.

duanejangula

The TV Cable. Can someone tell me if this cable is not properly adjusted, that damage could result to the tranny. Thanks.

mmadden55

There is a spring loaded valve in the valve body that regulates this shift it is probably sticking . TRy a complete fluid and filter change may fix it. If not get a manual and tear it down.

Pro Built Automatics

If the TV cable adjustment is correct, (Max TV at WOT throttle) and the part throttle shifts are happening at the right time (and the shifts are too firm), then the feed holes in the separator are most likely too large. On the 1-2 shift, the accumulator being restricted will bring on rough 1-2 part throttle shifts also.

calidude

I know this is an old thread but I have an 85 with a 700R4 and getting a rough 1-2 shift and having the same as others where it works better once warmed up. It will screech tires on hard acceleration and jerk hard. I've already adjusted the TV cable and that didn't improve anything. Is there a maintenance item for the accumulator or something to resolve?

I'm assuming there is some kind of seal or rubber that could just be old...

duanejangula

I have a 1987 with 700R4 and I have same thing, hard shifts between 1-2... I was just told that's the way they are.. After it warms up, shifts are a bit smoother..

vorteciroc

Is this a new condition, a worsening condition, or an ongoing condition?

Fluid level and condition?

Any modifications made recently?

Mileage on the unit?

If this is anew condition and the Fluid is full and in good health...
I would like to see Line-Pressure readings, and know about any modifications made.

It is possible that the 2nd Accumulator Spring has broken/ corresponding Piston does not seal anymore.

vorteciroc

The books that we (Hydra-Matic Engineering and Buick Engineering) wrote for GM Techs to Learn this Transmission used to be found on EBAY from time to time.
Not so much anymore though.

Digital Copies do exist for download; search for the THM700-R4 Principles of Operation/ Technician's Guide.

calidude

Thanks answers above and appreciate your in depth knowledge!

Another interesting thing I see on cold startup is the car actually seems like it moves forward a bit while in park. Not sure if that is related?

vorteciroc

That would most often be indicative of a Clutch-Pack dragging...
The Forward Clutch for example in the THM700-R4.

calidude

okay thanks, any additional insight on the 1-2 shift?

72buickgs

Noting really wrong with a hard shift, if tranny has no problems, as u can adjust the hardness by adjusting the TV cable inward,

calidude

Thanks Gerry, yeah it improves on warm up... just trying to understand why it's an issue and what maintenance I would do to solve it

Camaro71

Thinking out loud: temperature related issues are related to hardened/hardening seals. Once oil is warmed up, the seals will soften and work correctly. Till this moment I can imagine leaking some oil and only shifting with more TV pressure/line pressure.

calidude

Yeah that makes some good logical sense to me, it’s a smooth shifting trans once it’s warmed up. Cars that sit and don’t get used just don’t run well I’ve found, gotta drive em

Any seal specifically?

Camaro71

In case of the 1-2 shift, I would be checking the 1-2 acc piston seal and the 2nd piston seal in the servo.

vorteciroc

As I posted before...
I would start out by taking a look at the 2nd-Accumulator Parts.

sofakingdom

iTrader: (1)

Also look to see if it has a B&M shift kit installed in it.

It's total crap; does that to make the n00bz that buy one and put it in, think that they've "improved" it somehow. Often ends up breaking parts. Main noticeable symptom of one is, EXTREMELY HARSH 1-2 shift.

Best way to find out would be, download the install instructions; and inspect your valve body closely to see if that's what's been done to it.

vorteciroc

I second the "B&M Shift-Kit is Crap"!

I refer to that line of Products as the UnEngineered "Shift-Kit".
Actually, I don't even like the Term: "Shift-Kit".

Anyway...
A guaranteed sign of B&M Parts installed, would be a Spacer/ short piece of Tubing that replaces an Accumulator Spring.
Some Accumulation on the 1-2 Shift is a good thing!
Quick, Firm, Positive Shifting is what we want for long and healthy Transmission Life.

Overly harsh Shifts are unhealthy for the Transmission/ Unnecessarily breaks Parts.
The 1-2 Shift for this Transmission, can very easily be made very firm if desired.
There are several correct ways to go about doing so...
Then there is of course is the wrong way (B&M).

calidude

Thanks guys, been doing more study on this and guess the early versions of the 700R4 prior to 87 has some challenges

The spring can break in the 1-2 accumulator and seems there are lots of aftermarket pin delete piston kits too.

If I get ambitious may remove and inspect.

calidude

yes this, thanks!