grim

So ive done some reading and have finally accepted that my syncros are probably bad. My truck will grind when up-shifting to 4th and 5th but id kinda like to understand what the grinding is exactly?

Also, when accelerating, if i bring 3rd up really high befor shifting, then 4th wont grind and same when i go to 5th.

and the other thing i dont understand, is that when im say, driving up a hill in 4th once the load becomes to much itll start to grind and ill have to slow down and put it into 3rd. is that also a symptom of the syncros gone bad?

and finally, i get a weird noise when going slowly in reverse sometimes. im not sure how to describe it. kinda like a really faint scraping or grinding?

brainfade

I hate to say it but it sounds like you have bigger problems than just syncros. Bad syncros would just affect getting into gear, if the trans is making noise under load there are bigger problems. Sounds like time for a tear-down and inspection

maybe368

There is a relatively easy way to check the performance of your synchros. If it is grinding while shifting, try double clutching while shifting. As any old timer knows, you only need the clutch for starting off and, if you double clutch correctly, you can shift like silk. In fact, you don't need the clutch at all once you are rolling. If it doesn't grind when you double clutch, but does when you shift normally, then the synchros are bad. When I was a new firefighter, many moons ago, we had fire trucks with 5 speed non-synchroed transmissions that were called crash boxes. You HAD to double clutch or you weren't going to shift...Mark

grim

ive tried double clutching and im not sure im doing it perfectly but i think pretty good. it doesnt eliminate the grind.

it also doesnt grind all the time it seems, that when i upshift, if im not going fast enough or have enough momentum, it will grind. Or if i hit the gas too heavy goin into the next gear itll grind but letting off will stop it.

Depending on road conditions, i can drive and shift with no grinding.
What would cause a grinding noise when under load at the bottom of a gear only?

GIT-R-DONE

I would pull it apart and find out before I would continue running it as you may cause more damage to it.

Crossy's son

When i double clutch the 93, it will slide right into 2nd, down or up.

Otherwise it won't let you even get near the 2nd gear gate and it'll grind bad.

So you wanna wind it out in 3rd, let off the fuel and push the clutch in, put the trans into neutral,then push clutch again and put it gear you want it should slide in, you wanna do it kinda fast though.

Mark Nixon

Grinding synchros is a symptom of the mainshaft having too much fore-to-aft clearance.
This is indicative of the worst case scenario, the input-to-mainshaft bearing has failed and is allowing the mainshaft gears to "float" and give the synchro assemblies too much clearance, which defeats the sychro rings.

The grinding up hill, with a load in 4th, is likely the mainshaft walking back and forth on the cluster, putting it into 3rd loads the cluster gear and eliminates the mainshaft walking.

This tranny is already in a VERY SEVERE condition!
So severe, I'm surprised you can even SHIFT it at all, but I'll bet it takes some effort, at least.

Mark.

grim

ive never driven one of these trucks befor, but its not that hard to shift into a gear. and it seems to drive pretty good (minus the occasionaly grind)

the grinding also isnt just in 4th it will do it in 5th and very rarely in third under the same conditions.


i also dont know if its related but my vehicle top speed is around 95 km/h would that be cause of tranny problems or is my truck just geared really low?

the PO told me he starts in second gear cause first is realllllly low

grim

anyone have any other tips? or is my trans just totally screwed? based on how well it still drives, it doesnt seem like such a severe condition.

could anything else cause these symptoms or sounds?

sootnsmoke

The only time you ever use first is to maybe get started up a steep hill while towing. Otherwise, I never use 1st gear. It is great for crawling in bumper to bumper traffic at 3 mph. You might just have low 4.10 gears like me. Just look at the rear differential tag/stamp and you will see the gear ratio as either 3.54 or 4.10 (lower option).