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post #1 of (permalink) Old 11-21-2002, 03:42 PM
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Noisy 4 speed trans. Normal?

85 CJ 7. Just got it running. Trans shifts perfectly but makes lots of noise.
the lower the gear the louder the siren noise is. 4th gear is quiet. The gear oil is full. Is there anything I can do to quiet it down?(Thicker gear grease?) I don't have carpeting so I'm hoping its normal. 128000 miles. Thanks for your anticipated help. Ralph P
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post #2 of (permalink) Old 11-21-2002, 05:45 PM
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Re: Noisy 4 speed trans. Normal?

Most, if not all, 4-speeds that have a granny low use spur-cut gears for low. By their nature they will make a lot of noise.

The intermediate gears on any modern transmission are helical cut, and should be pretty quiet.

Top gear in (as far as I know) all Jeep transmissions is actually a direct connection between input and output shafts, so the gears are just along for the ride, and the box is quiet.

If the noise is excessive, it almost has to be either a bad input gear or cluster gear, or the bearings that support them. In which case, heavier lube will make it quieter, but if it's the bearings that are bad, they will eventually ruin the gears too.
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post #3 of (permalink) Old 11-21-2002, 06:25 PM
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Re: Noisy 4 speed trans. Normal?

Jim Lou is spot on,

My guess would be the input bearing on the tranny.

I thicker thicker oil would probably hurt more than help.

the good news,if you can live with the noise, itll probably run like that for a while IF you keep it full of oil.
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post #4 of (permalink) Old 11-21-2002, 08:49 PM
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Re: Noisy 4 speed trans. Normal?

Another thing that can cause noise in other gears and quiet in 4th is the 4th gear synchro. I got a '85 5.0 Mustang for 50 bucks because the trans screamed in every gear but 4th. Had the trans rebuilt for $350.00 for and sold it for $4000.00.

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