brant914

Hello everyone.

my 1986 4x4 automatic started giving me problems yesterday. I've spent a couple of hours searching and learning. It looks like its one of a few problems, but I still have a couple of questions.

First a tiny bit of background
I bought this 7,000 miles ago and did a head gasket, new head, timing chain, full tune up, all filters including transmission flush and filter. (and I did also install a trans cooler out of fear)

previous owner's records indicated the transmission solenoid (s?) were replaced in the past about 3-4 years ago
I don't know if it was all 3 or only a single. I have a receipt but it contains no details.

Truck just turned 160,000 on sunday and the last 7,000 have been very trouble free. Truck shifted well and ran great. Of course its not too peppy but I attributed that to the automatic and found it to be normal/adequate

So... on sunday I had to travel to another state to clean out my grandmother's house (recently deceased) Its about a 250mile trip each way. The weather was terrible and the destination town last weekend was on accident alert. The truck was in 4high frequently at around town speeds but 2High during the highway miles to and from.

On the way back (sunday) the speedometer started bouncing a bunch. about a 10mph bounce. I disconnected the cable at the bottom when I got back and pulled the gauged cluster. I found it semi hard to turn and lubed it a bunch until it loosened up some. I put it together and drove it and within 2 miles it was bouncing again. I'm not certain its the cable, but based on it being hard to turn I assumed it was the cable and have a new cable on order currently (not here yet)

So I drive the truck for 2 days with a bouncing speedometer
then last night in town, at 20- 30 mph the transmission starts shifting poorly.

I have no blinking on the O/D light, but my description of the problem is that 1st gear feels normal. At 20mph it shifts up and then the truck is jerky and feels like it shifted from 1st to 3rd. It accelerates very slowly and feels jerky like its in too high of a gear. If I floor the throttle it shifts back down to 1st and is fine. If I accelerate to about 30 or 35mph it shifts into O/D and feels fine. If I manually shift the floor lever into gears it drives fine without the bucking

So my first reaction was that the solenoids are messing up and its shifting into too high of a gear? Perhaps hunting between 2nd and 3rd gear and bucking as it hunts?

I checked the fluid, not burnt and within the correct amount on the dipstick.

During my research I learned that there are 2 speed sensor and one is in the speedometer. It wasn't clear what year that document was referencing... so I'm not 100% sure that also applies to the 1986 models?
I also learned that the trans computer can be a problem as well as the TPS, temp sensor, etc.

I will pull out the FSM tonight and see how to pull trans codes if I have any (although the light is not blinking)

I would like feedback on my guesses of what to do next:

1) would the erratic speedometer effect or confuse the computer?

2) will driving it (I'm supposed to go out of town again this weekend) damage the transmission if I wait for the speedo
cable to arrive

3) is it the solenoids for certain. and thus no need to wait on the cable, go ahead and order the solenoids?

4) random thought... but would my trans-cooler without a thermostat installed be harmful in the winter. Did I cause my own problem?
(last weekend it was VERY cold and I was on the highway)


any input would be greatly appreciated
thanks in advance
brant

brant914

anybody have any ideas?
I'm afraid to leave town tomorrow at this point.
not sure if I should deal without a car in winter, or order 300 worth of parts ?

I posted a 2nd thread about codes
can anyone tell me how to check them for the A/T?

open to idea's
brant

maco35

Try adjusting your TPS B4 you start changing parts, I was having the same problem with my auto tranny until I checked my tps and it failed the test, it was bad, replaced it and the auto trans. worked perfect after that.

brant914

thank you
definitely worth a try
and I'm really just waiting on parts anyways so it can't hurt
thanks for the idea... gives me something else to research and learn about.



another symptom
when I start the truck it shifts fine runs normal and fine for about the first half mile and then starts to act up... don't know if that could be some type of idle circuit on the tps or cold transfluid?.... just an observation.

brant914

bump for help and more idea's
I'm off to the cold to check the tps this morning
brant

BMcEL

The first thing you need to do is test the throttle position sensor, following the FSM procedure to the letter. The TPS has a huge affect on how the transmission shifts. Until you do that, there's really no point in throwing guesses out there.

If you're having difficulty testing or adjusting the TPS, you could always disconnect it and see if that resolves the shifting issues. Just note that the cable from the trans to the throttle is actually for line pressure, not kickdown as many believe, and without the TPS, shifting will be based solely on the signal from speed sensor #2 in the transmission. This means you will need to manually downshift when accelerating since the trans will default to the highest gear for the speed you are traveling.

The speedometer cable will eventually snap if left fluttering too long. You could disconnect it until your replacement arrives if it bothers you, but speed sensor #1 (in the cluster, driven by the speedometer cable) doesn't affect trans shifting if the computer is getting a good signal from speed sensor #2.

Jkelley429

iTrader: (1)

yeah it probably the TPS. my dads chevy 1500 (am i allowed to say that?) was shifting weird(it tried to start off in o/d LOL), but it threw a CEL code. Replaced the TPS and it ran fine.

brant914

I've got to say it..
you guys are genius's

maco35
BMcEL
Jkelley429

you guys are right.
I went out and fought with the TPS
I don' thave the allen screws...
I am still not comfortable that the bottom stock screw is really tight (any tricks for that one?)

but it was out of spec
I re-spec'd it and passed all of the tests
I went around the block and I think its fixed.
I'll go for a longer drive tomorrow and put a few miles on it
but I think you all just saved me $200 in solenoid parts!

I'd like to buy you each a beer next time your in colorado
thanks a ton guys
I need that thing running for work so thanks a ton
(its way too cold for me to take a motorcycle to work right now)

and hopefully the new speedo cable arrives soon and fixes that little annoyance also.

brant

BMcEL

Glad you got it working right. When you replace the cable, take the extra time to lube it as well as the input on the cluster to avoid future issues. I didn't do that when I replaced mine and it still flutters a tiny bit.

Might want to clean the undercarriage before you get started too...you're gonna be bear hugging the motor and trans to get that cable in.

brant914

lithium or even wheel bearing grease? any recommendations on grease?

thanks for the tip!

brant

BMcEL

Lithium grease in the cluster and wet graphite film in the cable.

brant914

Long test drive update:

my problem is definitely better but not quite gone.
after 15 -20 minutes of driving when everything is warm
I still occasionally (1 out of 10 times) get the same problem
especially if I'm going up a slight incline

1st gear shift is fine
but I think its ocassionally going 1st to 3rd and then has a definitely shudder.... like its in too high of a gear

If I pull the floor mounted gear selector down from "D" to "S" during the stutter, I can hear/feal the down shift into what I assume is 2nd and then the shudder stops and I accelerate away

I should add that this only happens at light throttle now
if I tip in the throttle during the shudder the truck also down shifts and pulls away


So absolutely the TPS helped. I adjusted it a 2nd time from scratch thinking it migh be in a worn track or I might be able to tweek it better. My ohm readings came out slightly different on the second adjust, but still within spec. However the problem persists.


more questions:
1) this isn't a transmission lock up issue is it?
2) Should I buy a new TPS at this point?... since the adjustment made such an improvement (I changed nothing else except the TPS adjustment) I feel like you guys were all on the right track.

thanks again fella's
brant

brant914

bump for follow up...

is it time for a new TPS or do I still have something else causing problems?

brant

BMcEL

Does the TPS test to spec as outlined in the FSM? If not, it's time to replace it. Shifting from 1st to 3rd is indicative of a faulty solenoid.

You should post a pic of the 'S' on the shifter lol.

brant914

my shifter has been relabeled.
when I got the car someone had tried to "clean" the indicator or something... it is all jacked and relabeled.

is it not supposed to be an "S" ?
is the indent between 1st and drive for 2nd gear.... when I manually pull it out of drive and into "S" it down shifts and stops studdering so I assumed that was 2nd gear?

The TPS did come out within all of the fsm specifications for a 1986 after I adjusted it. (both times I adjusted it)... I wondered if it might have a dead spot or worn track internally since the shifting issue is only at very slight throttle when I hold the throttle pedal still, and then only occasionally now that the adjustment was completed.

I also noticed during my adjustment that I have a tiny bit of play in my throttle butterfly-shaft I can gently close the shaft and get one reading on the ohm meter... but when I let the spring close the butterfly hard it is a slightly different reading on the ohm... I pulled the TPS off and held the shaft from each side and could feel a tiny bit of give or wiggle... I'm not sure if this is exasterbating my TPS readings to the ECU

would a solenoid fail intermittently?
I'll look into ordering a set... and research the aftermarket TPS's also...

brant

BMcEL

VCC-E2 should remain constant, regardless of throttle position. If it jumps around while cycling the throttle, the TPS is bad.

VTA-E2 should steadily increase in resistance as the throttle opens. If you get an erratic reading at one or more points between closed and WOT, the TPS is bad.

If someone replaced the solenoids in the past, I wouldn't hesitate to test them. You never know where they sourced the parts or if they knew what they were doing.

brant914

BMcEL,

thanks again for sticking with this and all of the help
is this your day job?... you know your stuff!

VCC-E2 was constant

I had one blip on VTA-E2 where the readout dropped, but then couldn't recreate that with another 3 or 4 tries... so not sure if my connection could of caused it rather than the TPS

(I also noticed that VTA-E2 is higher at rest on the throttle stop and then takes an initial drop as you begin to open the throttle.. but then consistenly rose after that... is that normal?)


I think I'll repeat the test in a day or two and see if it drives worse or better in the mean time. I'm also going to order a trans filter and gasket in preparation of testing the solenoids. I searched threads and saw others recommending to apply 12V power to the removed soleniod and listen for its action. Is there any other tests or just a working/failure situation?

thanks for putting so much time into my issue
brant

BMcEL

Haha nope, I work for an electrical contractor...early Toyota pickups/4runners are just an addiction.

Depending on your meter, it may have not had enough time to react to the dead spot in the VTA track. Cheap and older meters have a slow response time so you have to cycle the throttle very slowly to pick up an imperfections. Troubleshooting the transmission control system:

http://personal.utulsa.edu/~nathan-b...34electron.pdf

phildelfino

needs some links? here's a good one for autos.

http://www.pirate4x4.com/forum/showt...highlight=a340

brant914

just an update for future searchers with similar problems.


I want to first THANK everyone that helped me diagnosis this. I learned a ton and didn't even realize how interconnected the different components were
THANK YOU all for your help.


So I lasted posted with an occasional (1 out of 10) intermittent upshift problem. The tranny seemed to still be upshifting into 3rd when I was going slow enough to be in 2nd. The truck would stutter because it was in too high of a gear

I had previously ordered a replacement speedometer cable due to a recent and violent bounce that had developed in mine. But the cable was factory and took about 10 days to get

in the mean time I bought a (CRAPPY!) off brand TPS for $75 thinking that I was going to have to replace the TPS, shift solenoids, and even ECU to solve my problem.

I had adjusted the stock TPS 2x and it definitely helped the problem but reduced it down from frequent to occasional.

I put the new TPS in and couldn't get it adjust at all. I took it out and bench tested it against the used factory one. It had a dead short and was a real piece of crap. I wasted an hour trying to fight that lower phillips head, only to have to reinstall the used one and reset it for a 3rd time.


The truck still had the occasional bad shift and stutter.
the next day my new speedometer cable arrived so I installed it.

So far (only a couple of hundred miles) my problem is solved....

wow.. it must have been the speedometer cable all along.
no more bounce on the speedometer, but now the tranny holds 2nd gear until around 30mph and drives normally with no quick upshifts.

I'm theorizing that the "bounce" in the speedometer was telling the ECU that the truck was going faster than it actually was.

I know that the speed sensor inside of the tranny is supposed to be the primary sensor for the ECU, but I'm not sure if mine is bad or what.

So far I'm just happy its shifting and driving normal again and I'm going to just keep using it and road testing it in the mean time.

YOU GUYS ARE AWESOME.... I don't know what I would do without this place
thank you
brant