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I searched the forums and didn't see my particular issue so...

 

My 1987 Sunrader (18 ft w/auto trans & OD 145k miles) has an issue with staying in 2nd gear when the shift lever is in the '2' position and it seems to be related to the throttle. If I am going down a steep hill and put it into 2nd, it will not stay there unless I take my foot completely off the gas. If I am giving it some pedal, it will shift into 3rd and if I subsequently release the gas pedal it will shift back into second. 

 

It also seem to do this on level ground, when using second to accelerate and get up to speed. Under those conditions I can start out in 1st and when I manually shift to 2nd it immediately does so, which appears to mean that the linkage adjustment is ok. Likewise, when off the gas it shifts down into second as it should when I move the shifter to position 2.

 

From reading the Chilton and Haynes manuals it does not appear that there are any vacuum lines (i.e. modulator) running to the trans, which appears to be the A43. 

 

I read somewhere the the TPS may need adjustment but have not tried that yet as it is not easy to get to.

 

Has anyone run into this or have any ideas?

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Well I'm at a loss as to why you would shift to 2nd to use the tranny to help braking but want to use the gas for one. Still don't know why it's happening though. Is your fluid level good, is your tranny getting too hot. Can you get this to replicate going uphill. Some places I need it in second to get up the hill and then you would be using gas. Does yours do it then. Does it shift normally when in drive? I never use overdrive because it can create high heat problems that will eventually kill your tranny so lets leave that out of the equation for now. 

Linda S

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The hill in question is 12 miles long at 6-7% grade so I have to use engine breaking to avoid frying the brakes. When I put it in 2nd to do so it shifts out of 2nd into 3rd unless I take my foot off the gas, which causes it to shift back into 2nd. With it in 2nd and foot off the gas it slows it down too much.

 

Never seen an auto trans do this on any other vehicle except when the shift linkage was out of adjustment. The previous owner is deceased so I can't ask him about it. Even if the throttle kickdown cable was out of adjustment it that wouldn't seem to cause it to auto shift up to a higher gear than what is selected, but I guess I'll look at that next.

 

Just wondering if anyone has run into this before.

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What you are reporting is normal. It is related to the throttle cable as soon as you press the pedal it thinks it's time to up shift it is what controls the shift points. There are no other inputs to the trans other than the throttle position. No Vac lines, electronics etc. If you don't touch the gas it should continue to retard.

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17 hours ago, linda s said:

Well I'm at a loss as to why you would shift to 2nd to use the tranny to help braking but want to use the gas for one. Still don't know why it's happening though. Is your fluid level good, is your tranny getting too hot. Can you get this to replicate going uphill. Some places I need it in second to get up the hill and then you would be using gas. Does yours do it then. Does it shift normally when in drive? I never use overdrive because it can create high heat problems that will eventually kill your tranny so lets leave that out of the equation for now. 

Linda S

I changed out the fluid and filter screen less than 100 miles ago and the fluid level is within the marks. The trans shifts smoothly with no slippage or other sign of distress. 

 

When I was going uphill it didn't happen but I was not fully releasing the gas.

 

It operates normally in drive, with the shift points being affected by throttle position, so it will hold second if I have my foot into it and shift into the higher gear when I back off on the pedal. 

 

OD works but I only switch it on when I am on level ground at highway speed or on a gradual downhill to avoid bogging the engine. 

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All is good, what your dealing with is a function of throttle position AND road speed AND governor speed.

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Jamblin, I'm more aligned with your thinking, that sounds odd to me.  I don't think it should be shifting into 3rd.  I have similar situations driving the Rockies here in Colorado, Denver area, where yep I'll leave it in 2nd but give it a touch of gas when the grade lessens, I haven't encountered what you have.  Since you've changed the fluid, possibly needs someone knowledgeable to check shift linkage - but seems unlikely since otherwise I believe you'd see no difference at all when you use it, clearly that's not the case. 

 

So I'd think something is going awry & I'd probably pay someone to look at it.  Or check with  https://www.yotatech.com/forums/f116/ these guys if you're 2nd or 3rd generation truck, or find the right forum for other...    "Foot off the gas" changes vacuum & that's part of controlling shifting.  I'd suspect weakness in something related.

 

WME of course might be right & it's normal, seems like the more I learn, the more gaps in my knowledge get uncovered...

Edited by tstockma
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The Toyota trans has no vacuum control, mechanical linkage only. The 2nd a 3rd gen are electronically controlled to a good extent. Yes there is a correlation between throttle passion and vac but Toyota does not use vac as a bench mark.  What he OP said is normal operation totally controlled by throttle passion. Bottom line they are killer transmissions doing an impossible job in an over weight truck!

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  • 2 weeks later...

So, this does not make sense if this is as the factory designed it, especially on a 1 ton chassis where you would expect to be using engine breaking with or without a load. Every other truck I have driven with an auto trans does not shift beyond the gear selected unless the shift linkage was out of adjustment but this is usually obvious unless you always operate it in Drive, never manually downshifting.

 

One test I might try is to temporarily disconnect the kickdown cable and see if it still does it. 

 

I've worked as a mechanic and been wrenching for 50 years and it does not seem to me that the shift linkage is out of adjustment since it shifts crisply between gears otherwise, but I will doublecheck it.

 

@tstockma, I did post on yotatech a while back but got no responses so I gave it a bump. 

 

 

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I suspect no one answered on Yotatech because no one had a clue. I've spent several hours searching for a similar case and have found not even one example other than yours. I'm usually pretty good at finding things too. If you figure it out please let us know and I would repost on yotatech about the issue too. I figure for every problem there has to be a first and yours might just fit that bill. Just wanted to ask have you ever tried shifting to 3rd when you feel this mystery shift. Does that do anything or does it feel exactly the same. Just wondering if maybe what your feeling is the torque converter releasing. 

Linda S

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I'm completely stumped too.  I agree with Linda - let us know what you find out, if & when you do - could turn out WME is right & there's a moving part which he knows about, & it's working as designed - however it doesn't match what I experience in my rig.

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That is a very popular transmission used in the Toyota pickup, cab over, motorhomes, box trucks up into the mid 90's. Volvo used them and a wide range of larger Toyota cars, it will hold on decel as long as you keep your foot out of it. The shifting is governed by two things governor and throttle position (the cable) they are what have to be in agreement. Take it to a transmission shop or tell them what you are experiencing there is a caveat make sure they are a member of ATRA (automatic transmission rebuilders association) they are independent not franchised and have a reputation to uphold. I worked for one in the 80's and into the early 90's did all of their standard transmission and a great deal of automatics. According to your comments the transmission works fine except when you try to out think it, it pretty much means there is nothing wrong with the transmission.

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On 1/9/2021 at 11:38 AM, linda s said:

I suspect no one answered on Yotatech because no one had a clue. I've spent several hours searching for a similar case and have found not even one example other than yours. I'm usually pretty good at finding things too. If you figure it out please let us know and I would repost on yotatech about the issue too. I figure for every problem there has to be a first and yours might just fit that bill. Just wanted to ask have you ever tried shifting to 3rd when you feel this mystery shift. Does that do anything or does it feel exactly the same. Just wondering if maybe what your feeling is the torque converter releasing. 

Linda S

If I shift into 3rd when it is in second with my foot off the gas, it shifts into 3rd. If I have my foot on the gas it is already in 3rd so nothing changes when I shift it into 3rd. 

 

I have 50+ years experience wrenching on cars and trucks and have worked as a mechanic and have never seen the situation where an auto trans would shift up beyond the selected gear unless the shift linkage was out of adjustment. My trans shifts crisply and feels solid in general.

 

If others in Googleland have seen this non-standard behavior with this transmission they either just shrugged it off as a quirk or no one else has seen it. Since we would be more likely as a group to have downshifted on a downgrade to control speed, but no one else here seems to have run into it, I might have an outlier.

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On 1/16/2021 at 9:36 PM, tstockma said:

I'm completely stumped too.  I agree with Linda - let us know what you find out, if & when you do - could turn out WME is right & there's a moving part which he knows about, & it's working as designed - however it doesn't match what I experience in my rig.

 

Do you have the same tranny in yours?

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On 1/17/2021 at 11:51 AM, Maineah said:

That is a very popular transmission used in the Toyota pickup, cab over, motorhomes, box trucks up into the mid 90's. Volvo used them and a wide range of larger Toyota cars, it will hold on decel as long as you keep your foot out of it. The shifting is governed by two things governor and throttle position (the cable) they are what have to be in agreement. Take it to a transmission shop or tell them what you are experiencing there is a caveat make sure they are a member of ATRA (automatic transmission rebuilders association) they are independent not franchised and have a reputation to uphold. I worked for one in the 80's and into the early 90's did all of their standard transmission and a great deal of automatics. According to your comments the transmission works fine except when you try to out think it, it pretty much means there is nothing wrong with the transmission.

 

I wouldn't call it out thinking it. The only trans I know of that will downshift to compensate for a grade is the 6 speed Allison in my GMC pickup, if it is in tow/haul mode. All of the rest I've driven; GM and Mopar have stayed in the gear selected.

 

If no else has seen this issue with this model trans under similar circumstances then the next thing to try is adjusting the throttle/kickdown cable.

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All of us with an automatic and 4 cylinder engine have the same transmission. I have  spent 15 years tracking down solutions  for our members on the internet and like I said yours appears to be the only one. We would love to know when you figure it out or fix it. 

Linda S

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On 1/23/2021 at 3:24 PM, linda s said:

All of us with an automatic and 4 cylinder engine have the same transmission. I have  spent 15 years tracking down solutions  for our members on the internet and like I said yours appears to be the only one. We would love to know when you figure it out or fix it. 

Linda S

 

Ok, will do, but will have to wait for it to warm up a bit...

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On 1/23/2021 at 12:51 PM, Jamblin said:

 

Do you have the same tranny in yours?


Yep - A43, in an '86 21 foot New Horizon, 22RE engine.  Looks like between my dad who had first & me, we've done two fluid changes at 40-45k mile intervals, and it's possible the original owner did one before dad got it at around 45k.   ...I speculate you may have something internal beginning to go, but it might last a long time before it need fixin'.

Edited by tstockma
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These little transmissions are over worked as long as the fluid is changed on regular intervals they will last a long time. There is a caveat if the mileage is high and the fluid is dark and never has been changed do not change it or there is a real risk you will be walking within a few days. The stuff that is on the clutch packs are actually protecting them new fluid is very high in detergents that will wash the stuff off the clutches. Another thing to look out for is the output shaft bushing if there is a lot of play at the yoke replace the bushing it is the rear support for the output shaft and will eventually trash the governor bore inside of the case if the bushing goes bad.  

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Oh yeah baby!   My dad might never have changed tranny fluid on any car before he got this Toyota rig, but did his research - he concluded at 45K dropping the pan was safe to do, so paid for a proper change - then at 91K last summer, while I could have dropped the pan, instead I did the proper method for unknown history or very old rigs.  Pull tranny fluid out the drain hole & top it up, drive gently for 100 miles (be sure to work each gear shift position), repeat, drive another 500-1000 miles & repeat.  Done.   Immediate improvement in shifting.

 

When weather turns warm again, having learned from posts here, I plan to check that output shaft for any play or other signs of issues - that's the one weakness people talk about, on these overworked reliable old A43's.  I only recently saw apparently you can insert a sleeve over a shaft that's been scored, rather than more serious surgery, if a new seal doesn't stop any leaks.

 

Maineah, I really value your knowledge & experience, & Linda, & others like you.  Keeps me coming back.  (Still miss Derek too.)

Edited by tstockma
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OK here is the deal on the governor bore it is the case! now somewhere out there in transmission land there is someone with the tools. It requires boring the case and pounding in a  sleeve read overhaul any way this is why I say keep an eye on the output shaft. It was not real common usually high mileage and probably neglected things like leaking rear seal. The tail stock is much simpler it comes off and yes I'm sure someone will have a repair sleeve and if needed a new drive shaft yoke. With the exception of the iron case 5 spd 4WD Toyota has always had pretty tough transmissions.

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