Manual Transmission T56 | T5 | MN12 | Clutches | Hydraulics | Shifters

3rd and 5th gear grind

Thread Tools
 
Search this Thread
 
Old Feb 9, 2016 | 03:21 AM
  #1  
DylOrr's Avatar
Thread Starter
Teching In
iTrader: (1)
 
Joined: Oct 2012
Posts: 15
Likes: 0
Default 3rd and 5th gear grind

I want to start out with the story of this car. I purchased the car with a locked up motor as the guy ran 87 fuel on a 93 tune and it absolutely destroyed it. I got the car back together and the slave was leaking so I just took it to a shop to have a new one put it. When I took it there they put a new master, line, and slave on the car (o'reillys brand). After I got it back it was grinding 3rd at WOT shifts. I asked the previous owner and he said it never did grind on him (I believe him after meeting him and talking with him). So to my stupidity, I changed out the fluid with AC Delco Syncromesh thinking that may fix the problem. IT DIDNT . IT GOT WORSE. It now grinds 3rd and 5th with any pressure shifting. If I granny shift it it seems to be fine. I only put maybe 20 miles on it with the synchromesh and switched it back to regular Dex III and it seems to be doing the same thing. I only drove it about 5 miles after fluid change and parked it because I didn't want to mess anything up any more than it could be. 4th and 6th gear are like butter even at WOT. It has an eBay clutch the PO put in it.

So heres my question. What do I do? Is it possible that the hydraulics on the car are garbage? Is something wrong in the trans? Before I tear too far into it I would like to get a consensus on what people more knowledgeable than myself think. Clutch fluid looks clean. Should I bleed it out good?

Thanks for any input!
Reply
Old Feb 9, 2016 | 05:22 AM
  #2  
Carlos01SS's Avatar
TECH Resident
iTrader: (4)
 
Joined: Apr 2003
Posts: 832
Likes: 2
From: La Mirada, CA.
Default

I had problems like that, I had to wait a good second to go by before I could shift from 2nd to 3rd and 4th to 5th. Downshifting was a no-no if I was doing it fast, or even speed shifting wasn't a good idea.
My factory tranny had 108K miles on it, found out it was the synchro shims, and I needed new 3rd & 4th & 5th forks replaced.
I figured since they dropped the tranny to go for a total rebuild, replacing the factory paper thin synchro shims to carbon fiber(excellent replacement material, far superior to factory synthetic material) and forged shift forks and brass fittings as opposed to plastic.
$3k
worth it though.

This was only because I had to get my synchro shims replaced, hopefully for you this is not the case.
Reply
Old Feb 9, 2016 | 10:19 AM
  #3  
calhoon's Avatar
TECH Fanatic
20 Year Member
iTrader: (6)
 
Joined: Oct 2002
Posts: 1,967
Likes: 4
From: Charlotte metro area
Default

First thing to do is see if the shifter stops are mis adjusted....assuming its an aftermarket shifter. This is supect because you only have two gates( forward) that are problematic. Throw the stops away, they do nothing.

Carlos: There are no shims for the synchros and the paper synchro lining is NOT synthetic, it is an organic material. There is an iron 3/4 shift fork available to replace the OE aluminum part, however forging is NOT part of the recipe and is hardly needed. The aluminum 5/6 fork is not problematic and I have never seen this in alternative material. Brass fork shift pads will wear very fast ( not a good choice over the nylon stockers) . The correct upgrade material is a a bronze alloy, but some just use brass. The best fork pad upgrade material is an engineered bearing-grade plastic , like Vespel.
Reply
Old Feb 9, 2016 | 11:28 AM
  #4  
DylOrr's Avatar
Thread Starter
Teching In
iTrader: (1)
 
Joined: Oct 2012
Posts: 15
Likes: 0
Default

Originally Posted by calhoon
First thing to do is see if the shifter stops are mis adjusted....assuming its an aftermarket shifter. This is supect because you only have two gates( forward) that are problematic. Throw the stops away, they do nothing.

Carlos: There are no shims for the synchros and the paper synchro lining is NOT synthetic, it is an organic material. There is an iron 3/4 shift fork available to replace the OE aluminum part, however forging is NOT part of the recipe and is hardly needed. The aluminum 5/6 fork is not problematic and I have never seen this in alternative material. Brass fork shift pads will wear very fast ( not a good choice over the nylon stockers) . The correct upgrade material is a a bronze alloy, but some just use brass. The best fork pad upgrade material is an engineered bearing-grade plastic , like Vespel.
I'll look into that. This is my first m6. I'm an automatic guy. Are the shifter stops on the shifter itself, like underneath?
Reply
Old Feb 9, 2016 | 12:57 PM
  #5  
DylOrr's Avatar
Thread Starter
Teching In
iTrader: (1)
 
Joined: Oct 2012
Posts: 15
Likes: 0
Default

After looking more into it. I'm almost positive I don't have shifter stops. I believe it is a stock Hurst shifter.
Reply
Old Feb 9, 2016 | 02:29 PM
  #6  
calhoon's Avatar
TECH Fanatic
20 Year Member
iTrader: (6)
 
Joined: Oct 2002
Posts: 1,967
Likes: 4
From: Charlotte metro area
Default

The stops would be at the shifter stem where it comes out of the shifter. Stock and factory Hurst shifters do not have stops. However, if the shifter boot were torn it could allow road debris into the shifter and restrict the lever movement.
Doesn't cost much to look/ check it out.
Reply
Old Feb 9, 2016 | 11:04 PM
  #7  
DylOrr's Avatar
Thread Starter
Teching In
iTrader: (1)
 
Joined: Oct 2012
Posts: 15
Likes: 0
Default

Checked the shifter and all was good. Drove it 30 miles and 3rd gear seems better but 5th and 6th are grinding.
Reply
Old Feb 10, 2016 | 06:47 AM
  #8  
SSSTANG#1's Avatar
TECH Enthusiast
15 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (14)
 
Joined: Oct 2009
Posts: 617
Likes: 6
From: GA
Default

Check disc to flywheel air gap. Needs to be at least .050" for proper disengagement.
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

 Pouria Savadkouei
story-1

Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

 Verdad Gallardo
story-2

7 Most Reliable High-Performance Engines GM Has Ever Built

 Verdad Gallardo
story-3

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-4

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-5

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-6

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-7

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-8

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-9

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo




All times are GMT -5. The time now is 05:16 AM.

story-0
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

Slideshow: We take a close look at the ONE and Artidiag 800BT2 diagnostic tools from Topdon and the reasons to buy one over the other.

By Pouria Savadkouei | 2026-05-28 11:05:11


VIEW MORE
story-1
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.

By Verdad Gallardo | 2026-05-26 18:23:54


VIEW MORE
story-2
7 Most Reliable High-Performance Engines GM Has Ever Built

Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.

By Verdad Gallardo | 2026-05-21 16:45:27


VIEW MORE
story-3
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-4
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-5
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-6
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-7
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-8
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-9
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE