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hardsteppa

RB25DET gearbox rebuild issue, 4th gear locked

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so have finally finished putting the box back together, but now it's all assembled and housings are back on, I have an issue where it's locked in 4th gear constantly and will only turn by hand in 4th or neutral, but the whole shaft turns in neutral, not just one end. It selects all gears fine but won't turn in any other gear. Before I put the housings back on I confirmed all gears select and shift as they should and all turn accordingly with the gear selected, but once the front housing is back on, it locks up. I stripped it back down to make sure hadn't made any error in reassembly and the syncros bearings etc all sitting as they should, and everything was fine but as soon as the front housing went back on, it locks up again. I haven't filled it with any fluid yet so I'm thinking maybe is there too much friction on the 4th syncro when it's dry? (although I did put a little grease on it on it when reassembling for the 2nd time, hasn't made any difference). 

This box was a 2nd-hander off gumtree so I never actually used it myself to know of any issue with it prior. At a standstill with it now so, ideas are welcome.

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Definitely sounds like 4th synchro is not letting go. Usually some oil squirted there fixes it and sounds like you're onto it being a dry problem. Have seen that happen on our boxes, and have had calls about boxes doing that with new sychros we have supplied.

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Thank you once again for your help. I was going to give it a part-fill before putting it back in the car and give it a thorough turning over to get oil over everything; hopefull does the trick.

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and, yep :) good as gold now it has some oil in it. 

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tenor.gif

Thought so new kid 😄 good stuff 😊

Squirt some actual oil around the sychros next time you do a box and I bet it'll never happen again to you.

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Hey mate on a more serious note, please tell me you used Threebond 1207C sealant on the bottom three front cover bolts and NOT threadlocker (or even worse nothing) ? Had to pull my dog box out of my 32 on the weekend, after the one box we didn't do ourselves that we had Neat Gearboxes do for us, pissed oil out of the front cover. Noticed a slight drip under bellhousing and though fcuk, they didn't did they ? Found this as expected....

 

 

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WP_20191012_17_16_51_Pro.jpgPretty annoying to pull a box out to reseal 3 bolts, but Sam was very apologetic after I showed him the stuff up. We didn't check front cover before install, but why would we. It was done by a place that knows what they're doing so it can happen to anyone. It is in the Nissan manual after all...

Check, check, check

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