bwillcutt Posted March 24, 2012 Share Posted March 24, 2012 hello have a spicer 1420 transmission its a 5&4 air shift all in one box the problem i have is when you shift the air shift part it grinds a little it completes the shift fine it just grinds shifting up or down doesn"t seem to matter what gear in the main or what position on the air shift just wondered if anyone has any ideas its in a 1981 autocar thanks ben Quote Link to comment https://www.bigmacktrucks.com/topic/24079-spicer-sst1420-3a-transmission/ Share on other sites More sharing options...
smorse54 Posted March 24, 2012 Share Posted March 24, 2012 Hi,had the same transmission in a 1979 RWL770LST. Did the same thing, never was able to make it smooth. Finally replaced it with an RTO14613 Fuller after 500K miles of being pissed.The dealers said it was normal. Good luck,Steve Quote Link to comment https://www.bigmacktrucks.com/topic/24079-spicer-sst1420-3a-transmission/#findComment-109935 Share on other sites More sharing options...
theakerstwo Posted March 24, 2012 Share Posted March 24, 2012 I guess you are using the clutch to shift the rear box ant you? Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/24079-spicer-sst1420-3a-transmission/#findComment-109942 Share on other sites More sharing options...
bwillcutt Posted March 24, 2012 Author Share Posted March 24, 2012 yes i bump the clutch to shift it up or down it shifts great it just grinds a little i"m used of the fullers and they shift so smooth haven"t had much experience with this old spicer Quote Link to comment https://www.bigmacktrucks.com/topic/24079-spicer-sst1420-3a-transmission/#findComment-109943 Share on other sites More sharing options...
theakerstwo Posted March 24, 2012 Share Posted March 24, 2012 When that trans was around i know a few guys that had them and i have worked on them and drove them some.If the driver is used to trhem thay shift with out grinding but only thing drivers didnt like was having to cltch on ever shift. Also check the grease and it should have a light weight grease. If its got gear end grease it will not last because it has neeedle brgs and the heavy grease would also make it harder to shift.Make sure the air pressure is up on it. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/24079-spicer-sst1420-3a-transmission/#findComment-109945 Share on other sites More sharing options...
bwillcutt Posted March 25, 2012 Author Share Posted March 25, 2012 i'm not sure whats in it for oil but looks pretty light may even be synethic looks clean no smell Quote Link to comment https://www.bigmacktrucks.com/topic/24079-spicer-sst1420-3a-transmission/#findComment-109996 Share on other sites More sharing options...
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