The old “popping out of 2nd” song and dance

1950 - 1952, M38, questions, discussions, regarding anything related to the M38.
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wc56daveyboy
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The old “popping out of 2nd” song and dance

Post by wc56daveyboy » Mon Feb 01, 2021 2:57 am

So.. recently inspected transmission and transfer
Case before installing. Transmission internals looked fantastic. Was visually inspected and checked before installing in the jeep.
Nothing looked or felt worn.

Now that it’s running about during my “debugging” phase I noticed it jumps out of gear on a downhill coast in 2nd gear.

I do not relish the thought of removal again so I’m looking for answers before removing from jeep

Searching for answers on this site brought up this:
Generally 3 things cause the synchro to pop out. Worn or damaged synchro, Worn shaft bearings and/or pilot bearings and of course not being fully positioned correctly by worn or improperly installed shifter fork.
The last comment is what I wish to explore further before I tear this transmission out.

In the case of this transmission, I wish to note that action of the shifter Tower / assembly.

From neutral to say 1st or reverse, there seems to be a long “throw” and a very positive engagement

2nd however seems like a very short “throw” into place from
Neutral.

Is this an indicator of a shift tower problem that can be adjusted somehow?

Or is this a sign of internal wear of gears or syncros indication perhaps something was missed upon inspection


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Re: The old “popping out of 2nd” song and dance

Post by mdainsd » Mon Feb 01, 2021 4:15 am

I do not think so. The long throw in 1st and reverse for that matter is because in those cases you are moving gears their full width to engage or disengage. 2nd and 3rd however require much less movement, only the width of the synchroniser ring, so less lever movement.
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Re: The old “popping out of 2nd” song and dance

Post by wc56daveyboy » Mon Feb 01, 2021 4:46 am

So perhaps the shifter tower operation, as I described it, is normal?

I got another T-90 in the shop

It’s a civy t90 so the shifter is different.
But i think they interchange.??

I guess I could try a swap of shift towers and see
If there is any difference

If not I guess there was something missed in the transmission somewhere when inspected

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Re: The old “popping out of 2nd” song and dance

Post by Joe Gopan » Mon Feb 01, 2021 5:47 am

Second Gear Bushing is most common cause, the gear rocks back and forth on the shaft and the play accumulates every time you accelerate or decelerate in second gear. Best not use 2nd for compression braking, it is murder on the Jeep 2nd hear. Too muh play kicks it out of second on deceleration.
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Re: The old “popping out of 2nd” song and dance

Post by wc56daveyboy » Mon Feb 01, 2021 5:51 am

Thanks Joel
Best not use 2nd for compression braking, it is murder on the Jeep 2nd hear.
Really? Would have never guessed using 2nd gear like described caused that much damage.

In fact, in the hills around here I’m seldom
Out of 2nd!!

No hopes for an easy fix with the shift tower being the blame then ya think?
Ughhhh

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Re: The old “popping out of 2nd” song and dance

Post by Joe Gopan » Mon Feb 01, 2021 11:13 am

Learn to use the brake Pedal. Worn second bushing is chronic with Jeeps that down shifted into 2nd for slowing, showing off, etc. My M-38A1 has 70+ Miles, and is tight as new in 2nd. Have done dozens of T-90's with worn 2nd Gear Bushing over past 60 year tears or so and used to salvage the2nd gears by installing new bushings. Am lucky as OEM parts were available back then.
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Re: The old “popping out of 2nd” song and dance

Post by Joe Gopan » Fri Feb 05, 2021 4:50 am

Civilian Y-90 is the same as GI, the covers have the same internal parts. GI M-38/M-38A1 is made to allow the shift cane to be removed by removing the screw on cap. on the shifting cover. Civilian Cover fits the GI and vice versa.
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Re: The old “popping out of 2nd” song and dance

Post by wc56daveyboy » Fri Feb 05, 2021 5:05 am

Thanks Joel.
Haven’t looked into this further.

But I now have options

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Re: The old “popping out of 2nd” song and dance

Post by dpcd67 » Fri Feb 05, 2021 7:02 am

I've had jeeps like that; you just hold the shift lever with your right hand and steer with the left. Until you either get around to fixing it or you sell the jeep.
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Re: The old “popping out of 2nd” song and dance

Post by Joe Gopan » Fri Feb 05, 2021 8:40 am

The worn 2nd Gear Bushing play will allow the 2nd gear to nudge the synchro blocking ring which will cause it to shift to neutral. JEEPs require frequent monitoring of lubricant levels due to constant lubricant seepage. They are not like your cars which can get by with less frequent fluid level attention.
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HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: The old “popping out of 2nd” song and dance

Post by Sasquatch » Mon Feb 08, 2021 7:46 pm

Before you pull the transmission, remove the shift tower and replace the pins holding the shift forks to the shifting shafts. Roll pins are available at any good hardware store. If that does not solve the problem, then you have the fun of pulling the transmission for “renewal”.


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