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Shifting issue with AT
Hello all:
My car (91 Sidekick, 1.6 lit, 8 valve) auto tranny does not shift from 1st to 2nd gear when cold (even when the lever moved manually). I have done the following things to the car, but the issue still persists. Once the car gets warm (after say a couple of km of driving), the shifting becomes perfect, and car works perfectly.

I have:
1. Changed tranny
stuck in 1st cold 3L30 , very old 1970s designed, TH180 based hyramatic box.

lets look at this path way, the load path.
does the stall test pass? in 1s and reverse? (or drive)?
do the line pressure tests, in the FSM pass (this is test 2 on all A/T )

only a dead, or grossly leaking internally, MODULATOR can stop shifts. and would be worse hot. (thinner ATF)
Where is the other end of the vacuum line, that connect to the VM goes to? VM? what is VM? vac, mod, got it.
it goes to the intake manifold the A/T has this port below,

i think the gov can be replaced xfr case off.
we can see this here.
part 770 off
and 685 dismantled, ive never attempted it, but others have.

see the red line?
the red paths are marked.? and that blue path is very important.
the word LINE is the pump main line, and is LINE tests, done with gauges.
in Drive.
full line pressure arrives at DRIVE red , goes to the GOV, if packed #7 screen the gov is born dead. the governor shifts trans based on MPH speed, tail shaft RPM controlled.
The 1>2 shift valve is (controlled by GOV blue line) if dead, there will never be a 2nd gear. nor 3rd as the pressure from 1>2 valve gates to 2>?3 valve. (hydraulic logic,)
the 2nd clutch has seals (large) that sure can leak.

if the gov works, and the 1>2 valve changes to 2nd
then the 2nd line goes hot.
there are many thing on this 2nd CL (clutch ) line that can leak. cold. the accumulator is one as is the 2nd apply clutch seals.
all old seals love to leak, and can do so cold, when they warm up, they get softer and start sealing proper
this can happen at any point , of the system.

keep in mind, it might be the total combined leakage. of all seals ,(many) that makes the 1>2 fail.
fixing one leak, then later the problem returns for age on the other leaking seals, progressing to entropy as they all do.

the tests are , stall test. passes in 1st.
then line pressure, if line pressure fails, then all is lost.
if line is good, stall good, line pressure is spec. and mod is new.
then GOv screens.

the modulator (not bad or leaking) will delay shifts only on engine load, (vacuum = load)
that is its only function. and can not stop 1 to shifts. if its not leaking inside.
some mod valves fail. and leak and bleed all that precious GOV line feed, to the case, dumping the line. making it useless. this is not your failure.

[Image: 3L.jpg]

#7 is the "screen assembly",
[Image: governor.JPG]

[Image: manifold%20differences.jpg]
Thank you very much for your time and in-depth info.
Wow; there are many things I should be doing to find the culprit.
I have never done the Stall Test, but I will attempt it in this coming weekend.
As for part 700 coming off; I have to take a closer look at my car; I thought that part was attached to the Transfer-case, and to take that off, I should be taking the Transfer case off. Obviously, that may not be so (will check).

I will keep you (and everyone) posted of my progress (hopefully)!.
The car-nut.

PS. BTW, when I took the old VM out to replace it with the purple stripe one, almost 1/4 quart of AT fluid poured out of the transmission. Is that usual?![/b]
the stall only takes, 5 seconds.... bam done. its just making sure the transmission dont slip.
the line pressure tests can not be done with , a slipping tranny, im sure your 1st gear does not slip.

ok this is 2wd, and has 2 form factors. the 4wd is one form too, 3 total,
the 5sp transfer case is same as 3 speed, 4wd.

what car is this?
(91 Sidekick, 1.6 lit, 8 valve) how many doors, 2wd or 4wd. ?
the 5 speed has a dry center case
but the xfr case bolts to the 3sp flange directly. the 3speed is sold to suzuki with this special 4wd flange.

the 3 speed rear flange has its own, shaft seal, just like the front of the transfer case.
so when you spit this line, no oil leaks.
but when you remove the 3sp flange bolts that is a wet line.
it will leak ATF like mad.

yes the valve body is above the pan and is full of ATF, it never fully drains, with pan off too. think of the Valve body as a huge sponge.

when same with the TC, huge volumes of ATF.
Thank you for the reply.
Mine is 2 dr, 4WD.
I am happy to report that my shifting problem is resolved after adding one can of Seafoam transmission treatment!

Now to be fair to the purple stripe vacuum modulator, whether it had any part in resolving the issue or not shall remain a mystery. The reason being that I took a ride after replacing the VM and the shifting was improved somewhat. Then, I added the Seafom, and took a ride, and the shifting got improved somewhat again (i.e., after replacing the VM, it shifted after 0.6 km of driving, and after adding the Seafoam, it shifted after 0.4 km). The next day, it shifted after 0.2 km, and on the 4th ride, the day after, it shifted immediately.

I just wanted to describe the situation exactly for those who have the same issue or will encounter the issue in future.

Thanks for your help.

there are many ATF additive treatments sold for A/T boxes, that can make the seals to get softer (chem actions) and start sealing right now.
most are just a band- aid, as the seals will not be really fixed. they are just chemically attacked. but is a great way to get out of a jam, no?

i hope im wrong, but any A/T rebuild shop will tell you , this is true. (and the books ) (they get the trans, after all that fails eventually)
when the seals get old and hard, they are bad.
but one can in fact, use the treatments.
after a while the treatments are not able to soften the seal any more. they do have a limited life, this is for sure.

the stripe code is just body weight, codes. over 22 old cars used this trans , and many weight class codes.
nice list. and the Grumman LLV
the VM for any LLV will down shift way too soon, on hills, and drop economy in direct measure.

for sure, see let us know how long it runs on this magic sauce.. 1 week, 1 year?

here is the magic sause answer from the pro site.

the fact is , what did that additive do to the seal, organics.
is it going to fail harder. if yes , then it will never shift again, even hot. (it's a risk , that)
when does it end the softening magic?????
that is the big question?
I agree that this should be a temp fix (if VM had no role in here, which is hard to say).

My guess is that the governor screen is the culprit. Soon, when I get a chance, I will attempt to get my way to the screen.

Thanks again!
The Car-nut!
if a stump puller kick, anything works
for daily driver.
id have a used (off a wreck) trans on my bench , and doing a full overhaul.

the vm color is a fine tuning, of steepness of hills that cause the down shift. (heavy car, low HP engine sooner, but light car, very much HP, its down shifts for only pikes peak r)
its really just the spring tension inside it.

i hope its the screen. but the screen

the labor time, to fix a 4wd screen is almost same as kit job on a used tranny..

check out and read Clill Ruggles books on topic. i have both his. gm turbo 400 book is great.

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