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Lash Russell Member 
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Hello all, After I did a five speed (Getrag) conversion I started running with 75-90 weight lube but found the shift up to second could be a little crunchy at times. I am now trying 20-50 and shift up to 2nd is fine but down to first requires incredible timing to get right without grinding. 20-50, I'm sure to nobody's surprise, is a little louder. Has anybody had good luck with different weights/synthetics/additives etc in keeping the Getrag happy with a long life? Thanks, Lash |
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Brett Gibson JH5 20497 Member
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Synthetic 75-90 works well in my 5 speed box. |
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Greg Fletcher Administrator 
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Ditto what Brett said. The 20W 50 engine oil is fine for the thrasher 4 speed (it's recommended for that), but I would never use that in the Getrag. Parts for those are unobtainium now and you will benefit from a high quality, synthetic GEAR oil of the recommend weight. |
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Lash Russell Member
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Thanks Brett and Greg, This makes sense and I'll switch out to the synthetic 75-90. The reason I even tried the 20-50 was from a service bulliten that mentioned 20-50 was safe but loud, glad I asked. Lash |
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Lash Russell Member
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UPDATE, Mobil 1 Synthetic 75-90 put in, works great. A little quieter than 20-50 and able to manage all gears "crunchless" as long as I'm not too agressive. Lash |
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UKJames Member
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Reading this old post- I've got a 4 speed with a slight crunch into 4th- The box was refurbed recently but the previous owner installed, so not sure what oil he used. Sounds like the synchro might be slipping because the oil weight is wrong? Has anyone got a recommendation on the best make and weight of oil for the 4 speed box? Thanks- Jim |
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dbeliveau74 Member 
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Above Greg states: Ditto what Brett said. The 20W 50 engine oil is fine for the thrasher 4 speed (it's recommended for that), but I would never use that in the Getrag. Parts for those are unobtainium now and you will benefit from a high quality, synthetic GEAR oil of the recommend weight. |
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