trans slips into reverse

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if i'm going down a steep hill slowly and engage the clutch the trans slips into reverse and the only way out is to get the truck so the front is higher than the back. the gear selector seems as though its in neutral but the transmission is in reverse. this has nearly gotten me stranded a few times. it also happens if i am going slowly and brake hard with the clutch in.

what is worn?
 

65swb45

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Reverse in the Toyota 4 speed has its own dedicated shift fork and shift rail. This brings up two possibilities.

First is the possibility that the shift fork in the top cover is not resting in the pin allocated for it on the shift arm that moves the reverse idler gear. This is not very likely, as it would increase the odds that you would not be able to shift into reverse at other times when you need to.

Second is the possibility that either the detent ball or detent spring that nests inside the transmission tower [the upper half of the top cover] is missing. This would mean that you still have use of reverse, but that reverse isn't necessarily locked out while you are operating in other gears. This is more likely to be your culprit.

You will have to remove the [6] 8mm bolts [12mm heads] from the upper shift tower to investigate. Be very careful when you are removing the upper cover not to accidentally let one of the springs pull out and fall into the transmission case.

Best

Mark A.
 
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That is some strange $hit.

You can only be in reverse when the other gears are in neutral, so it can't just "slip" into reverse without popping out of the gear it is in. If it was simultaneously in R and any other gear, the tranny would lock up. The possibility of slipping out of gear and into reverse is so remote that maybe you aren't understanding the problem properly.
 
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it doesnt slip into reverse while it is in another gear. it slips into reverse when i am on a downward incline and depress the clutch to put it into first. before i get the chance to put it into first it slips into reverse. when i go to put it into first it is already in reverse and so i can't get it into first at all. then when i let the clutch out, thinking i'm in neutral, the truck starts moving backward. then i am in trouble until i get it onto an upward slope and it slides out of reverse.

the trans also slips out of first until engagement, unless i hold it into first manually.

sounds like i've got to have a serious look at forks, springs, and linkages.

thanks
 
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ok. i opened it up and took some pics. you can see the one spring that was there. should there be more in the other holes which have no bolt or spring in them? does anyone see anything unusual in these pics?
thanks.
x.jpg
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there is nothing holding your reverse gear in place .pin in the fork broke or if the top has been off maybey fork isnt in the gear .take the whole top off and check it
 
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i took the entire top plate off and nothing looks suspicious, loose or missing to me in the shaft/fork assemblies.

i'm going to try putting in these missing detent springs and see what happens. anyone got a couple of these in their pocket that they don't need?

another question: there is a setscrew on the outside of the box for the reverse idler. is this for adjustments?
 
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You can see from the pictures that the reverse shift fork gate (the one with the spring loaded button that you have to depress to select R) does not line up with the other gates and is partially engaged. Try moving it so it lines up exactly with the other two gates and see if it snaps into place with a positive detent or if it can easily slide back and forth. If it snaps into place and stays, then the detent balls and lockout pins are working. If it slides back and forthe they are worn and you need a new top cover (or tranny).

There is an adjustment for the R fork position on the side of the case with a lock nut. The screw has a punch mark and the intitial set position for the mark is straight up. If the R gear drags when you turn the input shaft with the tranny in a gear, then you can loosen the lock nut and turn the screw CCW up to 45 degrees until the noise goes away. It is possible that if this is not adjusted properly that the fork gate would be out of position as shown in the pictures.
 

65swb45

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You can see from the pictures that the reverse shift fork gate (the one with the spring loaded button that you have to depress to select R) does not line up with the other gates and is partially engaged. Try moving it so it lines up exactly with the other two gates and see if it snaps into place with a positive detent or if it can easily slide back and forth. If it snaps into place and stays, then the detent balls and lockout pins are working. If it slides back and forthe they are worn and you need a new top cover (or tranny).

.

Correction. Without the detent ball, the spring AND the force of the top cover pushing down on them, you will feel no positive detent as the fork moves back and forth. You CAN place the ball and spring into the hole, press down on the spring with your finger, and feel the detent as the fork moves into position.

As I suspected, replacing the balls and springs should solve your problem.

Best

Mark A.
 
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i actually found some springs today. stangely, though there was only one spring under the tower, there were three balls. hard to imagine someone thinking it would be ok to assemble the tranny without these parts. anyway, this weekend i will re-assemble and see how it operates. keeping my fingers crossed. i'll post with updates.
 
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problem solved. it was the missing springs. put in the new ones, bolted it back together and it works fine.

thanks for all the help:beer:
 

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