Hey, my situation is this. My car will grind from 1st to 2nd, and 2nd to 3rd if I shift fast. I believe my synchros are worn. If that is true, where can I get replacement synchros? Or even, where can I get a good rebuilt at in Southern California?

 

My car seems to grind like yours but only when the engine isnt warmed up yet. After a warmup it shifts perfectly, is that normal?

thewird

 

If it's grinding up top near redline, you might be able to get away with new tranny fluid. I recommend Neo.

If it's grinding anywhere from 2-5k rpm range, than you syncros are definitey shot or on it's way out.

 

Liem, it grinds only when I rev high. Usually when I'm driving towards redline.

 

I went to the dealer, and new synchros are 350 for a set I think, but I kind of want a low mileage tranny if the problem persist.

 

Do I have a syncro problem if it only grinds when cold?

thewird

 

I don't think so. Your problem just might be your oil. I'm going to change mine as soon as possible. When was the last time you change yours?

 

The low mileage tranny is attractive, but unfortunately there is a chance it will not work. I'll explain:

Worn synchros are *usually* the item blamed for rough shifting and clunky engagement. These parts are indeed the most influential, but 3 other things also have a major effect - wear on the gear teeth, wear on the clutch sleeve teeth, and choice of gear oil.

Using a true GL-4 gear oil (Redline MT-90 75w-90 stands out) is the best oil choice for synchros that aren't gripping well. The least effective gear oil for the synchros is a thicker, GL-5 or racing type gear oil, since their additives interfere with the grip of the synchros. If you don't get a non-GL-5 rated GL-4 oil, I at least recommend making sure the GL-5 you buy claims to be "yellow metal-" or synchro- friendly. Cold weather also causes these symptoms because the oil is thick until it warms up. If the cold weather is the big problem, go with a thinner oil, or simply take a moment and move the shifter more deliberately into each gear. (If you're already running a 75w-90, just slow down the shifts).

Second and third, the gear teeth and clutch sleeve teeth are the parts you feel and hear go 'clunk' when you get a rough shift. If you're getting this at high rpms, you'll round the sharp edges of these teeth and visibly distort their shape. So even if you replace the synchros, if these parts are damaged it still won't shift like new. Usually the more the synchros are worn the more these parts are worn too. These so-called 'hard parts' usually don't get replaced in a rebuild because of the cost - it adds a couple grand to a rebuild to change these parts, and in fact just doing the hub/sleeve/gear for say, 2nd gear, will cost $500.

So a low mileage tranny gets you all different synchros and all different hard parts. If it's a good one, you're getting a helluva deal. If it's been ragged on, it may not be any better than the one you have. I suggest that if you possibly can, go to the tranny importer, remove the lower cover, and inspect the tranny you're interested in. Sharp synchro teeth and sharp gear teeth are what you want.

Dave

 

how about grinding sound.. but very mild... on 2nd gear and 4th gear ? while 1 3 5 has no sound at all ?

 

JEFFF NOOOOOOOO!!!

put some neo in there and see what all goes down! i had the same problem, but neo did the trick :-D

 

http://www.bakerprecision.com/neogear.htm

Make sure you purchase 75W90 HD Competition Gear Oil. Since your down there changing the tranny oil, you might as well change diff oil too. One gallon is enough to complete both jobs.

 

usually the hubs do not wear near as fast as the syncros since the syncros are a much softer material, you REALLY need to mash on a tranny to beat up on those parts.

 

Yes, they are harder, but many, many transmissions I've opened up have significantly rounded hard teeth. They'll engage, but feel kinda clunky.

Dave

 

Ive noticed a very similar problem in mine, the car will grind something serious when i first start it cold.. and after about 5 minutes (or until warm) the grind goes away..

ill have to check the oil.. as this is the first time the car has seen the cold weather.. is there anything else i can check besides the oil that is a 'quick fix'? ive looked at used trannies too, but now im thinking twice

 

Also, try shifting slower. Like, when you pass through neutral, hesitate for a split second, then go into the next gear.

 

So you guys recommend NEO 75W90RHD Competition Gear Oil for the Tranny and NEO 75W90 HD Competition Gear Oil for the Diff? Am I understanding this correctly? If so, is this for any application or just for worn sync?

 

When I shift slow, it doesn't happen. The oil I used before was Royal Purple 75W90 gear oil. I guess I'll give neo or the other one, redline it was? a chance. I hope it fixes it. Freaking car! I just bought 2 gallons of Evans NPG+, 2 gallons os Sierra to flush the system out before I use NPG+, a GReddy radiator cap, and that cool yellow no spill cooling system burping thing. Now I'm going to have to buy freaking gear oil. When does it stop! haha! It's all good.

 

I don't think the neo or redline will be any better than the RP. These are all top-shelf gear oils.

Shifting slower is about the only thing you can do aside from change out the synchros.

Dave

 

Roger