Synchro Issues (1st Gear) E-series Gearbox

Hi Guys
 
Driving my '94 SW20 to the cinemas last night when I noticed that when shifting from 2nd to 1st I get a horrendous crunching unless the engine is idling or very close to it. While I don't have any experience with rebuilding gearboxes or anything I do know enough to be able to assume that my 1st gear synchro is completely shot. Every other gear is fine - both changing up and changing down. I do have the E-series box.
 
My first step is to change the oil - I know that this is only a bandaid but I've got the 200,000km service coming up as my next service so I'm planning on limping it through until everything comes out and I can have a proper look at it.
 
Questions:
- Any recommended oils? I've seen threads recommending a 75w-90 (pretty standard) but some people are swearing you should be looking for a GL4 instead of a GL5. Can anyone confirm or deny this?
- Is replacing a synchro easy enough to attempt to do myself? Or would I be finding more luck getting the guys at R&T to look into it? If that is the case how much could I be expecting to look at $$-wise...
- As far as sourcing Synchro's go, is it easy enough to go through Toyota to buy them individually or should I be looking elsewhere?
- Anything I should be aware of while looking into or performing any of this?
 
Cheers in advance
- Boof

Replacing synchros is not easy with special tools required, including a press etc.
 
GL4 or GL5 ??
Check outhttp://www.widman.biz/uploads/Transaxle_oil.pdf
Several GL4 oils are available but you'll have to search for them 'cos they're not stocked at places like Supercheap.
 
I personally have had very good results over a long period using Amsoil Manual Trasnsmission and Transaxle oil SAE 75W-90 GL4 (Amsoil product code MTG-01)  
 
Another good read:
(Toyota E code gearbox)
http://www.roadandtrack.net.au/index.php/techno/toyota
 
 

Go GL4 as recommended & it should get better. 3rd synchro is the most common to wear first.

dasic1
Once moving you shouldn't need to jam it in first unless you stop

Motorkhanas can be very demanding on 1st gear depending on the course.