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Drivetrain: HOW TO Fix Linkage Roll Pin on Transmission

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Drivetrain: HOW TO Fix Linkage Roll Pin on Transmission

Old 03-26-2009, 08:28 AM
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I have a set of roll pin punches from working on my AR15. Although I am not that confident of a roll pin in the shifter linkage application. Why didn't they use a stronger design, like a Grade 5 bolt perhaps? This $0.99 rollpin can cause a $2000 transaxle to blow up.
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Old 03-26-2009, 10:05 AM
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I tried using bolts. Every one of them bent, resulting in a really sloppy shifter with a lot of play/ You need something that can give a little. The tension/roll pin works perfectly for this. Plus would you rather damage your trans or break roll pins?
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Old 03-26-2009, 11:06 AM
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The way I understand it, breaking the roll pin can/will result in a damaged transaxle. I would rather use a captured device (pin, rod, bolt, or otherwise similar design) that wouldn't bend/break under those conditions.

Out of curiosity: What type of bolt did you use? Grade 5? Grade 8? Did you make sure that all of the loads were placed on the unthreaded portion of the bolt? An alternative might just be an unthreaded rod with the ends threaded to accept locking nuts and washers. It seems to me that the roll pin is there to both secure and locate the linkage assembly. I am not sure why GM didn't beef up this design, but perhaps I am missing something.
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Old 03-26-2009, 11:17 AM
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Originally Posted by metroplex View Post
I have a set of roll pin punches from working on my AR15. Although I am not that confident of a roll pin in the shifter linkage application. Why didn't they use a stronger design, like a Grade 5 bolt perhaps? This $0.99 rollpin can cause a $2000 transaxle to blow up.
Uh, no it can't. The reason they use a $0.99 roll pin is for it to break before you blow up a $2000 transaxle. It's the giving part of the system for when you are slamming gears. Which would you rather happen, break a $0.99 roll pin, or have a really strong bolt in there and **** up your shift forks or break something internally when the bolt doesn't give like a roll pin does?

Originally Posted by RedlineBrian View Post
I tried using bolts. Every one of them bent, resulting in a really sloppy shifter with a lot of play/ You need something that can give a little. The tension/roll pin works perfectly for this. Plus would you rather damage your trans or break roll pins?
bingo, this guy hit it on the nail.

Last edited by ralliartist; 03-26-2009 at 11:17 AM. Reason: Automerged Doublepost
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Old 03-26-2009, 11:17 AM
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darn it! u beat me to it!

the reason GM didn't beef up the pin is because if they did.... further damage would occur in the tranny, for example.... the stock clutch would probably burn out faster. breaking this roll pin will not result in damaging the transaxle, breaking this roll pin will simply result in a broken roll pin and then you'll have an extremely sloppy shifter "box" and you not be able to get the car in gear. it's actually a simple fix and replacing a .99 cent roll pin is alot better than having to replace a $2k tranny
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Old 03-26-2009, 11:20 AM
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Originally Posted by metroplex View Post
The way I understand it, breaking the roll pin can/will result in a damaged transaxle. I would rather use a captured device (pin, rod, bolt, or otherwise similar design) that wouldn't bend/break under those conditions.

Out of curiosity: What type of bolt did you use? Grade 5? Grade 8? Did you make sure that all of the loads were placed on the unthreaded portion of the bolt? An alternative might just be an unthreaded rod with the ends threaded to accept locking nuts and washers. It seems to me that the roll pin is there to both secure and locate the linkage assembly. I am not sure why GM didn't beef up this design, but perhaps I am missing something.
then you understand it wrong. Breaking the roll pin, PREVENTS the transaxle from being damaged. Using something that doesn't break or bend would cause something internally to break instead of a roll pin.

Personally, I used a grade 8 aircraft bolt in my linkages. I know that I'm at a higher risk now of breaking my transmission or causing severe damage. But I'd rather not be replacing roll pins every couple weeks. If I were to damage the transmission, I'd just replace it with a stronger one.

Originally Posted by rallycobalt06 View Post
darn it! u beat me to it!

the reason GM didn't beef up the pin is because if they did.... further damage would occur in the tranny, for example.... the stock clutch would probably burn out faster. breaking this roll pin will not result in damaging the transaxle, breaking this roll pin will simply result in a broken roll pin and then you'll have an extremely sloppy shifter "box" and you not be able to get the car in gear. it's actually a simple fix and replacing a .99 cent roll pin is alot better than having to replace a $2k tranny
I'm ralliartist and I approve this message. lol

Last edited by ralliartist; 03-26-2009 at 11:20 AM. Reason: Automerged Doublepost
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Old 03-26-2009, 11:25 AM
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oh a sidenote... very good how to man, i used this a month ago. my roll pin was in 3 pieces, when it happened i was freaking out because i thought my tranny blew but then after talking to a few members they said it sounds like a broken roll pin. i was like... then i did the almighty "search" and found this great how-to
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Old 03-26-2009, 11:29 AM
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What you guys said makes absolutely no sense. Traditional RWD transmissions have a direct shifter attached to the gearbox (e.g. 01-04 Mustang GT with TR-3650). As long as you don't act like an idiot and hamfist the shifter without letting the synchros do their job, nothing bad will happen. You could shift normally for 100k miles and nothing would go wrong. The linkages used on later transmissions add a lot of slop and even cause missed shifts due to the movement of the engine/transmission. The linkages on the FWD cars are the worst for this because of all the slop in the different joints/components used in the linkage assembly.

From an engineer's perspective, the rollpin is there to keep the linkages attached to whatever mechanism goes into the gearbox. It would make sense to actually use a stronger Grade 8 bolt/rod with an unthreaded section directly inside the linkage to prevent flexing and slop. I could see a number of ways the slop/flexing could contribute to transaxle damage akin to improper shifting (jamming the linkage or not letting it slide into place properly). The rollpin isn't there to prevent damage to the transaxle, GM probably used those rollpins to save a few pennies on the MU3/F35 and then deny warranty since many of you race your cars.
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Old 03-26-2009, 11:34 AM
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traditional RWD transmissions? that has nothing to do with what we are talking about here, so bringing that up makes absolutely no sense. RWD trannys & FWD trannys are 2 completely different styles.

i understand what your saying about using a stronger bolt.... but strengthening the bolt would cause the next thing in line to give way... and thats tranny internals. like we said... replacing a .99 cent roll pin is way better than replacing a $2k tranny.

now if you were to look at the hardcore race Cobalts out there (time attack, dragsters, etc.) they probably did come out with some type of bolt to slip in there, but that's for hardcore race applications. my stock roll pin held up for 40k miles, i'm sure the one i replaced it with will hold for another 40k. i actually did "upgrade" my roll pin though, i pressed in 2 smaller pins. i'm curious to see how that'll hold up.
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Old 03-26-2009, 11:43 AM
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Originally Posted by rallycobalt06 View Post
traditional RWD transmissions? that has nothing to do with what we are talking about here, so bringing that up makes absolutely no sense. RWD trannys & FWD trannys are 2 completely different styles.

i understand what your saying about using a stronger bolt.... but strengthening the bolt would cause the next thing in line to give way... and thats tranny internals. like we said... replacing a .99 cent roll pin is way better than replacing a $2k tranny.
With respect, before I get flamed, the reason I brought up a RWD gearbox is because the shifter is directly attached to the gearbox on some models. A FWD gearbox/transaxle is essentially the SAME, except your shifter is remotely attached - but it still has to interface with the gearbox at some point. A Corvette would be an example a remotely mounted RWD transaxle application (similar to a FWD application like the Cobalt) - again, the same concept applies. Instead of the shifter being directly attached, you work through several linkages. It only makes sense to eliminate as much slop as possible to give you precise control over the internals.

However, strengthening the bolt should NOT cause the next thing in line to give away because there is no reason to do so. If the shifter is designed properly, the reduction of flexing in the linkage at the gearbox would result in more precise shifting and less potential for damage to the synchros or other internal components.

Maybe I am explaining it wrong, but imagine yourself not pushing the shifter all the way through each position on the gates. That would result in transmission damage in the long-term since you're not engaging it properly before releasing the clutch. Added flex from a bent/broken rollpin would allow that to happen and result in transmission damage since you are relying on the linkage for precise shifting - yet it's not giving you that due to all that slop.

FWIW, I don't buy the idea that the F35/MU3 is a gearbox that needs to have linkages break to provide sloppy shifting, so I am going to borrow the Chiltons/Haynes manual and see if I can get a diagram of the F35 internals as well as look at the shifter assembly.

The reason I am curious about this is because the problem still exists on 08-09 SS/TC's and I have one on order.
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Old 03-26-2009, 11:52 AM
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i understand what your saying..... and i'll admit.... having this roll pin really sucks in a few weeks i'll be upgrading my clutch & flywheel, i'd like to find out if there is a bolt that i can put in there that'll last.... basically forever. it's really hard to say tho why GM didn't "bulletproof" that part of the tranny. what really sucks is that it's not covered under the powertrain warranty
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Old 03-26-2009, 02:08 PM
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GM has been using this transmission since 1984 in the Saab 9000 (according to GM). The 9-3 and 9-5 also used the same transmission. Does anyone know if those vehicles had the roll pin issues as well?
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Old 03-26-2009, 02:17 PM
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I don't think it is a roll pin issue, per se. It's a wear item resulting from shifting with more force÷time than the synchros can deal with, repeatedly. Looking at the roll-pin, vs bolt/dowel/stud debate: Looks like manufacturers choose the pin due to it's constant outward pressure (until they fail). A perfectly fitted stud with washers and lock nuts would accomplish the same task, albeit they wouldn't break as easily (if that is or is not something you prefer).
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Old 03-26-2009, 03:15 PM
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What kind of roll pins has everyone tried?

I found these at McMaster:

95765A417
420 SS Extra Strength Coiled Spring Pin 3/16" Diameter, 1" Length
In stock at $7.26 per Pack
This product is sold in Packs of 10

4500 lb double shear strength, Rockwell hardness C46
Suggest hole size is 0.185"-0.192"

Has anyone measured the ID of the linkage assembly hole?
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Old 03-26-2009, 03:21 PM
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the pin size is 3/16"x1"........i think, it's in the first post. i just bought a little pack of roll pins from AutoZone, cost $2.99, it had the roll pin i needed and like i said, i put 2 smaller ones inside it to see if that would help

Last edited by rallycobalt06; 03-26-2009 at 03:39 PM.
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Old 03-26-2009, 03:31 PM
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www.mcmaster.com
95765A417

3/16" OD, 1" overall length, heavy-duty (30% stronger than regular steel), and it is a coiled pin, think of it has being 1 sheet of spring steel wrapped as an eggroll.

I noticed a lot of people just used the cheap stuff they buy at the counter. The quality and strength could vary greatly.
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Old 03-26-2009, 03:42 PM
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Originally Posted by metroplex View Post
www.mcmaster.com
95765A417

3/16" OD, 1" overall length, heavy-duty (30% stronger than regular steel), and it is a coiled pin, think of it has being 1 sheet of spring steel wrapped as an eggroll.

I noticed a lot of people just used the cheap stuff they buy at the counter. The quality and strength could vary greatly.
dude.... that's a great find! i'm seriously considering picking up a pack. and then when the tranny shop is doing my clutch/flywheel i'll have them slip this in
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Old 03-26-2009, 03:49 PM
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Originally Posted by metroplex View Post
With respect, before I get flamed, the reason I brought up a RWD gearbox is because the shifter is directly attached to the gearbox on some models. A FWD gearbox/transaxle is essentially the SAME, except your shifter is remotely attached - but it still has to interface with the gearbox at some point. A Corvette would be an example a remotely mounted RWD transaxle application (similar to a FWD application like the Cobalt) - again, the same concept applies. Instead of the shifter being directly attached, you work through several linkages. It only makes sense to eliminate as much slop as possible to give you precise control over the internals.

However, strengthening the bolt should NOT cause the next thing in line to give away because there is no reason to do so. If the shifter is designed properly, the reduction of flexing in the linkage at the gearbox would result in more precise shifting and less potential for damage to the synchros or other internal components.

Maybe I am explaining it wrong, but imagine yourself not pushing the shifter all the way through each position on the gates. That would result in transmission damage in the long-term since you're not engaging it properly before releasing the clutch. Added flex from a bent/broken rollpin would allow that to happen and result in transmission damage since you are relying on the linkage for precise shifting - yet it's not giving you that due to all that slop.

FWIW, I don't buy the idea that the F35/MU3 is a gearbox that needs to have linkages break to provide sloppy shifting, so I am going to borrow the Chiltons/Haynes manual and see if I can get a diagram of the F35 internals as well as look at the shifter assembly.

The reason I am curious about this is because the problem still exists on 08-09 SS/TC's and I have one on order.
ok, just to enlighten everyone, WHEN the correct size roll pin is in place and not stretched or broken, the shifter will be nice, firm, and stiff and shift without any problems. It is when the driver shifts very aggressively that it stretches/breaks the roll pin and you have to replace it. This allows your synchros to stay alive and well, and let that little "easily" and "cheap" replaceable roll pin take the beating.

Does that make sense? It shouldn't be sloppy at all when the correct roll pin is used.
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Old 03-26-2009, 03:51 PM
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Originally Posted by rallycobalt06 View Post
the pin size is 3/16"x1"........i think, it's in the first post. i just bought a little pack of roll pins from AutoZone, cost $2.99, it had the roll pin i needed and like i said, i put 2 smaller ones inside it to see if that would help
this is a really smart idea. And this is actually recommended if you drive aggressively (race).

But, I used a 3/16"thick x 1 3/4" long Grade 8 Aircraft Bolt and it will not break. But, I do risk breaking the trans.

Last edited by ralliartist; 03-26-2009 at 04:54 PM.
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Old 03-26-2009, 03:51 PM
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makes sense to me
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Old 03-26-2009, 03:59 PM
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Originally Posted by ralliartist View Post
this is a really smart idea. And this is actually recommended if you drive aggressively (race).

But, I used a 3/16" 1 3/4" Grade 8 Aircraft Bolt and it will not break. But, I do risk breaking the trans.
ok so what i did will be fine then..... that's a relief
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Old 03-27-2009, 07:02 AM
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The closest match to a cap screw (bolt) I could find on McMaster:
94081A153

10-24 thread (0.190" OD), 2" long, made of titanium. It is not rated for any SAE Grade, but the min. tensile strength is 50,000 psi (I found a Grade 8 bolt was rated for 150,000 psi). The cost is $4.72 per bolt.

Be aware that the threaded portion of any screw/bolt is the weakest link. It is best to use an unthreaded pin/rod and just thread it at the end where you need to use a nut/cap to capture the pin/rod.
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Old 04-04-2009, 07:29 PM
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Bump for any news about roll pin fixes.
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Old 04-04-2009, 08:35 PM
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what do you mean any news?
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Old 04-05-2009, 07:32 AM
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Has anyone tried a proper roll pin fix instead of the chinese pot metal stuff they find at Autozone or Home Despot?
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