LT77 Hard to get 5th - Overhaul

My 50 suffix D LT77 gearbox from my 1986 Defender is very hard to get into 5th unless you have the engine speed just right. Miss it and back to fourth it is and try again.
I got fed up with it so have pulled out the gearbox. Going to have a go at an overhaul myself. Any suggestions what I am looking for that will cause this? Can’t afford an Ashcroft box and don’t want to change parts I don’t need to.

the synchro springs often break they look like a large c shaped spring x 2 ,baulk ring worn ,does it grate ,later baulk rings were coated and this sometimes wears off ,if you can remove rear seal collar and 8 x 10mm bi hex bolts fastening rear casing 2 x 13mm headed bolts inside at top you can remove rear extansion housing without disturbing main gearbox ,put a couple of shorter bolts to hold main box together while you work on 5th gear 5th gear synchro hub is sometimes tight and needs a special puller tool ,coated baulk rings should have 15 thou between them and gear when held on firmly non coated 25 thou

Look on the Ashcrofts site. I believe they say on there.

I tried them. They use to have a technical section but. I could not find it. Dont want to buy one of thier DIY kits for 145 pounds if I only need a few parts. Any further thoughts: it is to be a long. Term fix.

Ashcroft Transmissions - LT77 FAQ's

Ashcroft Transmissions - R380 FAQ's

you can buy whatever you need ,i can tell you how to do it if your interested,i have rebuilt too many to count the hardest part is removing seal collar and 5th synchro hub it is even possible to do when gear box is stiill attached to engine as long as you dont disturb joint between main case and rear brg plate