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jdt10768

4-speed Transmission compatibility late to early

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1970 4-speed 2002 vin 1674882: My transmission is a bit crunchy when shifting into different gears. Unless I'm at the perfect speed / rpm it grinds a bit going into the next gear. Maybe that's normal, but I don't think it should be. It doesn't jump out of gear, just a little grinding.

My question: Is a later model (1974) 4-speed transmission a direct fit replacement for the existing early model 1970 4-speed trans?

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yes, although the shifter will be a tad different.  If you get the chance, run the shifter mechanism that comes with the later trans. 

 

-selector rod joint

-selector rod

-shift lever

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If you get the chance, run the shifter mechanism that comes with the earlier trans. 

 

Andrew and I disagree about this.  But that's ok.  He's wrong. ;)

 

Opinions aside, with a 1970, you run a chance of having the old style synchros.

They shift great, but not for long. They will make you a better driver.  The later style

shift more smoothly.  And last a lot longer.

 

The one other thing to think about- if you're graunching all shifts, you might have clutch trouble.

Or clutch hydraulic problems.

If it's just not going cleanly into 2nd, it's most likely the trans.

Either way, you'll have it apart, and clutches don't cost all that much.

 

t

 

 

  • Haha 1

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Thanks guys, I always like several opinions and your disagreement makes me smile - maybe more of a smirk

 

Truly, the situation is not that bad. And if I concentrate on making clean shifts I can do better. But there are times when I just expect it to shift cleanly, and it doesn't - maybe because I'm in a hurry or at wrong RPM etc

All shifts are not graunchy, just sometimes. And it's not horrible grinding, but just a quick feedback from the trans of an unclean shift 

 

I'll just try harder to shift at the right time / RPM 

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Have you tried fresh fluid?

 

t

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+1 for Toby....I have found that if you mix dexron ATF and GL-4 in a 50/50 blend it seem to work very well when the trans is cold and hot.  It also helps with shifting and cleaning out the box.  I was taught this, by the late Peter Delott.  my humbling $.02 cents worth.

Matt

 

To check your clutch hydraulics.... while stopped in neutral, press the clutch, shift into a gear, and hold for a little while, if the rpm's begin to drop without releasing the clutch pedal.  Then faulty clutch system.

Edited by Schnellvintage
additional info

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Coupla things...I've had very good experience with using RedLine MTL in both my '02s--the '69 with those fragile but oh-so-smooth Porsche type synchros, and the '73 with the much more robust but notchier Borg-Warner synchros.  

 

The Red Line made that 2nd gear downshift on the '69 much smoother (although mine has nearly no grinding after 49 years because I've babied it since new, knowing its fragility from the get go), and it took all the notchiness out of the 73's shifting.  

 

2 hours ago, Schnellvintage said:

To check your clutch hydraulics.... while stopped in neutral, press the clutch, shift into a gear, and hold for a little while, if the rpm's begin to drop without releasing the clutch pedal.  Then faulty clutch system.

Just want to be sure you know that Schnellvintage is saying that failing this test means you have a problem with your clutch hydraulics, not the clutch itself...

 

mike

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Thank you Mike, correct! Sorry I had 3 Manhattans (Bullet bourbon 🥃). When I posted last night.
Matt


Sent from my iPhone using Tapatalk

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1 hour ago, Schnellvintage said:

Sorry I had 3 Manhattans (Bullet bourbon 🥃). When I posted last night

Were these single cherry or two cherry?

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