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#1
11-06-2023, 09:54 AM
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M/T popping out of gear
What would cause a Muncie transmission to pop out of gear (1st) on hard acceleration? This has happened before, but at light cruising speed.
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LIFT HEAVY, LIFE IS TOO SHORT TO BE SMALL! |
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#2
11-06-2023, 10:45 AM
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Usually linkage adjustment
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#3
11-06-2023, 11:29 AM
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I know little about four speed transmissions but my brother had this same issue many years ago. The trans guy said it was a worn gear assembly. He replaced that and the problem went away. I found it odd the first gear would wear out.
Hopefully you get a better answer from someone more knowledgeable. |
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#4
11-06-2023, 11:36 AM
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Check Trans to bellhousing bolts. My old Impala loosened up and did that. Bad pilot bushing also can be a culprit.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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#5
11-06-2023, 12:09 PM
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Many years ago I had this problem and by replacing the synchro assemble and brass blocker rings fixed it.
Stan
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
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#6
11-06-2023, 12:40 PM
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Quote:
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
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#7
11-06-2023, 01:02 PM
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Thanks, I’ll crawl under there and see if anything looks out of place. Although the trans was rebuilt about 15 years ago, there can’t be 5k miles on it.
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LIFT HEAVY, LIFE IS TOO SHORT TO BE SMALL! |
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#8
11-06-2023, 01:22 PM
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Out of adjustment would be the quickest fix, also could be broken snap ring causing the mainsheet to move.
And as someone else mentioned, worn gear assembly. The little teeth on first gear that the synchro ring lines up with could be worn to a point where they won't help to keep shift hub engaged.
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64 Lemans hardtop 4spd, buckets |
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#9
11-07-2023, 08:44 AM
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All of the reasons stated so far can cause the issue. In addition to the ones listed there is also the possibility of the shift keys (or dogs to some) being worn.
The most common result I have ran into is the synchro teeth on the gear and slider. The synchronizer’s will give a grind or rumble feel/noise during the shift if they are worn or cracked. If it pops out after the shift is made and the shift was smooth, I would direct my attention to the synchro teeth on the gear and slider. There is a slight back cut on the teeth to hold the gear to slider connection together. Once this back cut becomes parallel or worse it will pop out of gear. I typically see the issue in 4th as the on off torque wears this location the worst in conjunction with the way the input shaft to main shaft alignment relies on the pilot/front/mid plate bearings along with the tail shaft bushing whereas all the other gears / sliders ride on the main shaft. |
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#10
11-07-2023, 09:12 AM
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Synchronizer is what came to my mind first. Maybe check motor and trans mounts. Loose shifter, or shift arm, bolts?
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