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Possible clutch pilot bearing, but on the NV4500 more likely too much endplay on the mainshaft. Lets the input shaft run off axis, which causes clutch drag and premature bearing wear. Also may have cooked the synchro lining material on R-1-2 (glazed over). That reduces the friciton coefficient which causes delayed synchro lockup. If the tranny will go into other gears at a stop (standstill) OK, I would suspect synchro lining wear/failure. If hard to shift into any gear, then other problems. Don't try downshifting into 2/1 grs at too high speeds. It kill the synchro linings, even though they are double sided on those gears. Reverse was always hard or impossible to catch on my 4500 until I rebuilt it. Try letting off the brake slightly (roll just a bit) as you shift into 1st or R to see if it helps ease the synchro stop ring into lockup.

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[quote author=dewclaw link=board=13;threadid=5551;start=0#48845 date=1033781676]<br>...<br>Now I dont know much about friction coeficients. [undecided]<br>Guess you mean insufficient friction of the synchro surfaces?<br><br>And the end-play, do you speak of &quot;up and down&quot; (verticle) play on the shaft -or- &quot;in and out&quot; (horizontal) play ?<br><br>One more item . I bought this truck used a while back. Im reasonably sure that the tranny gear lube ( synthetic 80w90 )<br>has never been changed. I have been meaning to change it , but something else around the house always seem to have a higher priority.<br>Nonetheless , if the lube is breking down , would this possibly be contributing to my problems .<br><br>[/quote]<br>Yes, the friction surface(s) of the synchro rings/stoprings. Just like brake linings; if overheated they will glaze over and holding power is greatly reduced.<br><br>Endplay: I mean fore/aft thrust. The factory calls for .002-.006 endplay on the main and countershafts (personally believe there should be none). There should be ZERO up-down/radial play on the input gear. If not, you are wearing out the pilot bearing in the flywheel as well as the input gear/mainshaft pilot bearing and thrust bearing.<br><br>Dodge/GM (NVG is a joint GM/ChryCo corp) call for their own synthetic gear oil which is a GL-4, NOT GL-5 (common) lube. My local dealers were getting $22-$28/Qt. for the stuff. GL-5 will supposedly attack the synchro linings and/or stop rings (have seen NO evidence of such on mine). I had to go into my 4500 so often, I just started running regular ol' 75W90 stuff. It's harder to shift when cold of course, but fine when warm. Don't recommend mixing synthetic/non-synthetics as can cause seal failures w/some types of seals (been there). <br><br>If you drain a small amount of oil out and it looks really dark, your synchro linings are probably worn. <br><br>Regards &amp; good Luck!<br>-Scott A.