Aaron_M

I just had my whole transmission rebuild and put a new cluth in my car so it should be good but if i downshift to second gear from 3rd or so it will almost grind a little eveytime and im reading stories of people who downshift from 5th to 3rd.I have tried downshifting while reving high and while not and it still grinds!This pisses me off because if i want to race i have to slow down below 20mph before i can downshift into second.Is this normal?I can downshift into 3rd from 5th with no problem unless im going real fast.Please help me on this matter.
Thanks
Aaron

Aaron_M

you can reply if you want to

cdrad51

My tranny is in not too good shape and I can downshift (with some effort) into 1st at 20mph. Grinding while downshifting = syncro gears are worn out, which contradicts the statement that your tranny was just rebuilt. Who rebuilt it?

84stock

iTrader: (5)

Mine was doing the same thing. I drained the oil, put in castrol synthetic and an additive, and wow, what a difference.

Siraniko

iTrader: (13)

True but there are other causes of grinding at high RPM. Check your tranny mount. At high RPM, the engine/tranny will twist towards the passenger side which results in mis-shift. Look at the gear shift at idle. Rev it and you will notice that the shifter will slightly move.

Aaron_M

I think it might be the oil cause it will grind sometimes in the morning just when switching from 1st to 2nd,but if i hold the cluth in longer then it wont.

Steve Shulz

Put some synth in it

Aaron_M

just put that in the transmission or do i have to drain it then change it with synthetic?What kind would you recommend

oni-dori

drain... always drain before you fill.

Siraniko

iTrader: (13)

adjusting the clutch pedal's push rod may cure that problem, assuming that the clutch assembly/hydraulics are in good shape.

BIG J MIXALOT

shiftin's fun

jayroc

You should to learn to double clutch and rev match. It will not grind if you rev match correctly. This is especially handy for getting back into 1st while moving.
Really, though, it shouldn't be doing that if you just got it rebuilt. Try some high quality synthetic like redline, amsoil, or royal purple. I personally don't recommend mobile 1.

Rotofire

what is double clutching? heard it on fast and the furious and i felt bad cuz i didn't know what they where talking about and that's not even an accurate movie.

jayroc

lol. Actually, I think that's the first time I heard it too, but I read a lot since then.
Double clutching allows your engine to match speeds with the transmission and rear end. Smooth downshifts instead of the hard engine braking you would experience without double clutching. It'd take me at least a page to explain how it works, and there are several webpages detailing it already...

yayarx7

If your tranny makes noise you always put the best oil you can afford, then drive it till it breaks. Redline is a good one. Amsoil is well known. I like Mobil one because it is easy to find.

First check your clutch adjustment and bleed the hydraulics to make sure your clutch is fully disengaged when you are shifting.

Double clutching is truly an artform, have driven many a vehicle with syncromeshless transmissions I still do not do it well. I tend to resort to not using the clutch and matching revs. It just comes more naturally to me.

Siraniko

iTrader: (13)

Double clutch if you still have the OEM parts. No need if your using a heavy pressure plate especially with 4 or 6 puck clutch. Once you let go of the pedal, it will immediately engage.

yayarx7

BTW in the movie they were refering to double clutching off the starting line when drag racing. This allows the turbo to spool a bit when lauching, mainly for those big turbos with lotsa lag, and some argue really only applies to awd vehicles.

Steve Shulz

Double clutching is a must for big rigs, clutch in to take out of gear and clutch in to put into next gear. Big rigs dont have synchro meshes so you have to do it. If your synchros are going it will lengthen your tranny. By far rpm matching is the best, I can go through all gears just by rpm reving and not even using the clutch, very precise though sometimes I miss and boy what a noise. At least on the fast-n-furious the RX-7's engine was turning in the right direction (intake to exhaust to rearwheel scene) They must have done their homework on some not all.

nofxpunk_541

double clutching = not needed unless your car was made before 1920...haha, and seeing as how rx7's wernt made until 79, i dont see why we even need to mention it...

ZachstylezRX7

Keyword : Needed.
I don't NEED to change my oil either. **** my car will still run...
Fact of the matter is, double clutching DOES put less stress on your synchros. Even though the synchros are made just for the purpose, you will see longer tranny life if you double clutch.
Not necessary at all, like you said, but there is a purpose to double clutching, however i personally don't do it unless i am on country roads.

As for the FnF comment about double clutching for the turbo to spool up:
I actually never thought of that, but i honestly think you are giving the movie too much credit. I believe Vin's line was:
"Granny shiftin' and not double clutchin' like ya should."
I think this refers to the shifting aspect of double clutching.
I agree though, that the makers of the movie wouldn't look like such quite the jack asses if they were talking about the starting line concept.

Zachstylez

813KR$

I think if your trans was just rebuilt, you should have NO grinding while changing gears. The gears will grind only if your synchro's are worn out or gone! ! ! Been their, done that !

10,000

Does your tranny have ANY leaks? You may have no oil in the tranny. You should double check.

Aaron_M

i dont know how to double clutch,It sounds like your saying push in cluth to take out of gear,Let go of clutch,Push clutch back in while shifting into gear.im sure it works but how is that any different then just holding in the clutch and putting it in gear?But anyways,How do you check the transmission fluid level on a manual?I have looked everywhere in the manual and i cant find a damn thing about checking the transmission fluid on a manual.The way i usually shift is while holding in the clutch im also pressing the gas shifting into gear then letting off the clutch.Btw when the transmission was rebuild i think i forgot to mention the clutch was replaced so it should be fine.

LongDuck

Since you asked about the 'famed' double-clutching; this is a line out of a movie that has nothing to do with your RX-7 unless you've replaced your tranny with a racing box that has straight-cut gears instead of helical cut gears and syncronizers...

Double-clutching is only used by truck drivers whose gearboxes have straight-cut gears because they can handle a higher torque load than helical cut. When you think of straight- vs. helical-cut gears, think of the pinion gear your starter which is straight cut. For helical, think of the blades on pencil sharpener (the kind with the handle that you crank as you sharpen).

Double-clutching is simply letting the clutch out between gears to keep the transmission spinning at an RPM that will help straight-cut gears mesh better when you put it into the next gear. IT HAS NOTHING TO DO WITH GOING FAST. It's a line from a movie, which was written by a liberal, know-nothing, idiot.

Your RX-7 tranny has helical cut gears because they're quieter, they don't have to handle high torque loads, they're easier to shift, and because synchronizers make it simple. Synchro's (as they're called) are brass rings on the input and output shafts that gradually allow the gears to engage. As the synchro's wear out, the angle of the brass ring extensions gets smaller and smaller, making the shift require more energy from you, the driver.

Eventually, when the synchro's are worn down to nothing, you'll have to RPM-match to get the tranny to shift without grinding. This is where you hold the clutch in (or not, if you're skilled) and 'blip' the throttle to get RPM's up to where your engine *will* be when you complete the shift (for downshifting). On upshifting, everyone RPM-matches to a degree, even if you're not thinking about it.

Let's dispel the myth about 'double-clutching' being faster, because it's not.

To check your tranny fluid level, there are 2 bolts on the tranny, one on the bottom, and one on the left side. The bottom is the drain, and the left is the 'fill' hole. Be sure to take out the Fill bolt FIRST - because if it's seized, and you drain, you're going to have a hard time getting fresh fluid in there, huh? Once you have it drained and flushed, replace the drain bolt, then add through the Fill bolt until fluid comes out the Fill hole with the car on an even and level surface. Replace Fill bolt. You're done.

Good luck, and "...if you can't find'em, grind'em!"

Nick-7

To double clutch:
1) Depress clutch
2) Shift to Neutral
3) Let go of clutch
4) Rev motor to proper rpm (takes practice)
5) Depress clutch
6) Shift to next lowest gear
7) Let go of clutch

This is all done very quickly, practice it slowly until you get the hang of it. I think it is fun and I don't even think about doing it any more. You are now on your way to silky smooth double clutch downshifts.