Synchro tolerances and overdrive installation

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   I have recently had my transmission out to fix bad synchros. I now have it all back together with new Crown parts. The blocking rings still seem too loose to me. Can some of you pros look at this and tell me if this is acceptable, and if it is not, how do I fix it?
2nd part of this question has to do with the overdrive. I have a big hole transfer case with a large rear bearing retainer/adapter. The bearing was loose in this adapter so I sent it back to Herm and he sent me another one that is tight. Now when I bolt the bowl gear for the overdrive onto the transmission output shaft, the "stick out" past the transfer case is .700. Herm's instructions say the stick out should be .667. I've taken all the shims out from behind the bowl gear, so now I don't know how to get the gear further into the case.

I'm tying these two questions together because I wondered if I pull it all out again and put some shims behind the rear bearing, if that would move the mainshaft forward enough to tighten up the blocking rings and at the same time take care of my out of spec bowl gear stick out?

Here's the video of the sychros.

Edited by smfulle - 03 Dec. 2016 at 9:27pm

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smfulle Members Profile Send Private Message Find Members Posts Add to Buddy List Member Sponsor Member Joined: 16 Sep. 2010 Location: Ogden, Utah Status: Offline Points: 6141	Post Options Post Reply Quote smfulle Report Post Thanks(0) Quote Reply Topic: Synchro tolerances and overdrive installation Posted: 03 Dec. 2016 at 4:48pm
	I have recently had my transmission out to fix bad synchros. I now have it all back together with new Crown parts. The blocking rings still seem too loose to me. Can some of you pros look at this and tell me if this is acceptable, and if it is not, how do I fix it? 2nd part of this question has to do with the overdrive. I have a big hole transfer case with a large rear bearing retainer/adapter. The bearing was loose in this adapter so I sent it back to Herm and he sent me another one that is tight. Now when I bolt the bowl gear for the overdrive onto the transmission output shaft, the "stick out" past the transfer case is .700. Herm's instructions say the stick out should be .667. I've taken all the shims out from behind the bowl gear, so now I don't know how to get the gear further into the case. I'm tying these two questions together because I wondered if I pull it all out again and put some shims behind the rear bearing, if that would move the mainshaft forward enough to tighten up the blocking rings and at the same time take care of my out of spec bowl gear stick out? Here's the video of the sychros. Edited by smfulle - 03 Dec. 2016 at 9:27pm
	Stan 48 CJ2A (Grampa's Jeep) 59 Chevy 1/2 ton Grampa's Jeep Build Thread

Joe Friday Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group Sponsor Member x 2 Joined: 26 Dec. 2010 Location: Jeep Central Status: Offline Points: 3654	Post Options Post Reply Quote Joe Friday Report Post Thanks(0) Quote Reply Posted: 03 Dec. 2016 at 8:52pm
	Well isn't that just peachy. I just lost my response to your note... So to recap, I think your nearing adapter is not seated. If it is, the synchro clearance is controlled by snap ring thickness and/or shims between the mainshaft and the rear bearing. You can cause the same symptom if the gasket between the trans and T-case is too thick. I have the OE snap ring assortment and may have either OE synchros or an NOS synchro hub assy. I won't be home till next friday to check.

smfulle Members Profile Send Private Message Find Members Posts Add to Buddy List Member Sponsor Member Joined: 16 Sep. 2010 Location: Ogden, Utah Status: Offline Points: 6141	Post Options Post Reply Quote smfulle Report Post Thanks(0) Quote Reply Posted: 03 Dec. 2016 at 10:17pm
	Just to be clear, those blocking rings should NOT be that loose, correct? How tight should they be? I've reread all the rebuild guides and found only one mention in passing that the writer "thought" there should be a .010 gap between the ring and the gear face, but no source is given. I have way more than .010. I think I would be happy with snug nut not binding. Joe, I'm pretty sure that the bearing adapter is seated, but I've been wrong in the past. What snap ring would change the distance on between the blocking ring and the gear? Are we talking about the snap ring on the front bearing? Where does one find proper shims to go between the rear bearing and the shaft. I have the shims that Herm had under the overdrive bowl gear. I think they should fit, but if I shim the main shaft forward to tighten up the synchros then I may need more shims to move the bowl gear back.
	Stan 48 CJ2A (Grampa's Jeep) 59 Chevy 1/2 ton Grampa's Jeep Build Thread

Oilleaker1 Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 06 Sep. 2011 Location: Black Hills, SD Status: Offline Points: 4412	Post Options Post Reply Quote Oilleaker1 Report Post Thanks(0) Quote Reply Posted: 03 Dec. 2016 at 11:09pm
	The Synchros look a touch loose to me Stan. Mainshaft endfloat is controlled by the rear bearing and it's play between the balls and the race , the mainshaft spacer between the bearing and the shoulder on the mainshaft , 2nd gear overall length, the synchro hub OAL, and the snapring on the front of the synchro assembly. Then you may have wear on the cone part of 2nd gear and 3rd gear( main drive gear.) If you put the synchro blocking ring on those two mentioned gears, there should be a gap between it and the blocking ring. If it fits too close on the cone part of the gears either the brass or gear is worn too much. The input or main drive gear will only go rearwards until the large snapring contacts the case. If the nose or throwout bearing slider does not bolt up tight against the snapring and the whole thing moves forward, that will increase the synchro gap up front. So, how much end float does a dial gauge show you have with the transfercase bolted up tight and the rear gear installed on the mainshaft? As Mr. Friday says, even too thick of a rear gasket will effect end float. It's a touchy item. The rear main bearing can move between the cases in the machined pockets. I've installed a shim between the case and rear main bearing on some of mine to stop this. I've also installed a longer mainshaft spacer. All will reduce the endfloat and move the mainshaft forward which tightens the clearance at the synchro assembly. ( by the way, I got my lockers figured out, Thanks) John PS, a shim between the mainshaft spacer and rear main bearing can also tighten things up.
	Green Disease, Jeeps, Old Iron!

TERRY Members Profile Send Private Message Find Members Posts Add to Buddy List Member Sponsor Member Joined: 22 May 2007 Location: BOULDER COLORADO Status: Offline Points: 3400	Post Options Post Reply Quote TERRY Report Post Thanks(0) Quote Reply Posted: 03 Dec. 2016 at 11:52pm
	Loosen the mainshaft nut holding the TC input gear and tap the mainshaft forward so you can see if any clearance is present between the bearing spacer and rear bearing.
	BOULDER 48 2A