1st gear bad synchros?

Hey y’all, I’ve been having some trouble shifting into first gear in my 1998 Tacoma 3.4 4x4.
So, when I come to a complete stop like at a red light and then go to shift into first it is quite difficult to put it in gear, really have to force it. Other times in the same scenario, it shifts into first like butter. I have adjusted the clutch pedal, replaced oil with Redline MT90(seemed to help a little), replaced slave cylinder, had new OEM clutch installed & the transmission rebuilt roughly a year and a half ago. Replaced the shifter seat and bushing. And this problem still occurs. It’s really frustrating. The only thing that seems to be left is the synchros. Maybe the master cylinder but I’ve tried double clutching and that doesn’t seem to help. Have you had any experience with this problem? What was your solution?
Thanks
-Kyle

 

If you have your foot off the brake pedal and sit in first for 10/15 seconds, will the truck start to creep forward on it's own? If you hold the clutch pedal for 10 seconds before engaging first does your issue still occur? Or if you see brake fluid under the dash from the master cylinder on the clutch pedal?

Another idea that's a little edgier would be to get under the truck and find a view into the bell housing at the transmission input shaft from either an inspection plug or possibly around the release fork and safely with the park brake firmly on, have someone in the vehicle with it running and have them sink the clutch and try to engage first. See if when it's difficult to shift the transmission input shaft is also spinning full speed or if it's at a full stop.

The 3 possibilities I can think of in order of likely hood is that
A.) the master cylinder is failing and not fully disengaging the clutch
B.)the transmission input shaft spline has a rough spot on it that's preventing proper clutch disengagement
C.) there is actually an issue with the transmission.

Whats the warranty on your transmission rebuild?

 

This is somewhat of a common problem for first gens.
I had this problem, but after replacing the shifter seat and bushing it cleaned it up so that first was a lot less problematic. It still isn't as smooth as the other gears but doesnt hang up and feel like I'm going to bend something trying to force it in.

Two things that did help when I was having those problems were:
At a stop when you are ready to go, clutch in, shift to second, then to first and then come out of the clutch. Seems to line things up.
Also, I found that when it was sticking and not wanting to go into first, pushing the shifter harder was worse, if I gently like only used finger tips to shift into first instead of full palm it found its way into first easier. Seemed like something with pushing with my entire palm on the shifter pushed things out of alignment enough for it to not want to go in.

 

While ive got a v6, i had a 3rz w59 and both transmissions seem to have a tendency to "lock out" of first and reverse more than other MTs ive driven. Like Rucas said, going to 2nd before 1st and 4th before reverse is a muscle memory ive developed to get into those gears easier

 

shifter seat bushing and Redline MT90 transmission fluid did wonders for making 1st easier to engage in my truck

 

Yeah, the synchros don’t really wear out on Aisin Trans. Most rebuilds only replace bearing. So I would ask the builder if they swapped them out with OEM.

As mentioned, after new shifter seat, I use Marlin Crawler, I’d lean towards over machined flywheel, master or slave.