Doug Nash 4+1 hard to shift when hot

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Re: Doug Nash 4+1 hard to shift when hot

Post by Baprace » Sat Jul 18, 2015 7:35 am

GuysMonteSS wrote:I don't know if there is a splined shaft under the dash or not.
I do know that the firewall does flex when the clutch pedal is pushed.
Also the bracket on the frame that holds the Z bar bends a bit.
But it does this all the time...
Maybe the flexing gets worse as it gets hotter,but it only does it sometimes.
Guy
You have your answer in the firewall flex, fix that and your issues will be gone.

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Re: Doug Nash 4+1 hard to shift when hot

Post by BCjohnny » Sat Jul 18, 2015 12:07 pm

Unless the driven plate has started to delaminate/warp, I'd say the release bearing is too far from the pressure plate, as advised. You'll have just enough total travel when cold, diminishing to not nearly enough due to overall thermal growth when hot. It's not a hot issues, it's a cold one.

The proper fix is to assess PP/TB clearance and correct. The short fix is to reduce the leverage rate of the linkages to gain more throw. How acceptably heavy the latter makes the pedal become might persuade you to choose the former.

[Edit: It is possible that the PP is not retracting 'squarely'. Pretty rare though with quality components.]
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Re: Doug Nash 4+1 hard to shift when hot

Post by sidestep » Sat Jul 18, 2015 12:22 pm

I agree 1/4-1/2 at the throw out bearing is too much. With an enclosed bellhousing the way I set the free play is pretty simple and reliable, but applies to mechanical linkage only.

With z bar attached at frame pivot and thru firewall Rod bolted to the top of the z bar, pushrod attached to fork side only, I pull fork with throw out bearing up against pp fingers, run the adjuster nut up to the hole in the bottom arm of z bar, than back it off half to one diameter of the hole itself and cotter in place. Some gm manuals from the mid to late 50's describe this as the correct procedure to set free play. I don't take it as gospel as there are other places in the system that can be manipulated but it does give a good baseline to start from.

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Re: Doug Nash 4+1 hard to shift when hot

Post by sidestep » Sat Jul 18, 2015 12:34 pm

I should have also said that when using that method it will show you right away if you have the right length throw out bearing, if your up against the finger and there's no thread left to reach the z bar it becomes apparent real quick.

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Re: Doug Nash 4+1 hard to shift when hot

Post by GuysMonteSS » Sat Jul 18, 2015 3:38 pm

sidestep wrote:I should have also said that when using that method it will show you right away if you have the right length throw out bearing, if your up against the finger and there's no thread left to reach the z bar it becomes apparent real quick.
This could also be the problem.
I am almost out of threads on the adjusting rod.
Although there might be enough to reduce the 1/4-1/2 clearance a bit...
Guy
'86 Monte SS,513 BBC,AFR heads,Bullet solid roller cam,Doug Nash 4+1 5 speed,Hurst Inline Shifter,Ford 9 inch Rearend.

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Re: Doug Nash 4+1 hard to shift when hot

Post by GuysMonteSS » Sat Jul 18, 2015 3:44 pm

Just had a quick look on Summit Racing.
The TOB I use now has a total length of 1.288 inches.
Hays shows another part # that has a total length of 1.475 inches.
Could this be the root cause of my troubles ??
If so,it would be a fairly easy fix.
Guy
'86 Monte SS,513 BBC,AFR heads,Bullet solid roller cam,Doug Nash 4+1 5 speed,Hurst Inline Shifter,Ford 9 inch Rearend.

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Re: Doug Nash 4+1 hard to shift when hot

Post by GuysMonteSS » Fri Aug 21, 2015 3:23 pm

Just wanted to give you guys an update.
I got a tall Hays TOB as well as a new Lakewood adjustable pivot ball.
The old pivot ball had been welded in so I cut it out cleaned the threads and put the new one in.
The new TOB is a bit taller and it is also bigger in diameter where it meets the pressure plate.
Now the clutch is easier to push and it goes into gear much easier,no more grinding in reverse.
I gave it a good workout today for several hours in and around town and a bunch of spirited back road driving and I gave the clutch and shifter a real good workout.
It shifted real nice and it put the fun back into my summer hot rod.
Before there was almost no adjustment left in the clutch fork pushrod and now there is lots,maybe as much as 4 inches +.
I lined up the clutch fork geometry "by eye" so it might not be 100 % ideal but it is hands down better than before.
There is still the flex issue in the firewall and "Z" Bar but that will have to wait for another time.
It would be easier to address those issues if the engine were out of the car.
Thanks for all the help.
Guy
'86 Monte SS,513 BBC,AFR heads,Bullet solid roller cam,Doug Nash 4+1 5 speed,Hurst Inline Shifter,Ford 9 inch Rearend.

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Re: Doug Nash 4+1 hard to shift when hot

Post by ChevyEFI » Mon Aug 24, 2015 6:44 pm

Instead of the cut and welded fork, next time you have it apart,

Swap out the Lakewood 15000 for a 15015. You can then use a straight fork, and the linkage will line right up.

If you were running a 153 flywheel, you could do this with an 82 Camaro or 84-88 Vette bellhousing.

G-body linkage is bad enough; toss the dog-leg fork any time you can!

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Re: Doug Nash 4+1 hard to shift when hot

Post by sidestep » Mon Aug 24, 2015 8:47 pm

This is really good information, thanks for sharing

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Re: Doug Nash 4+1 hard to shift when hot

Post by autogear » Tue Aug 25, 2015 9:14 am

Glad to see you got it squared away. Don't wait forever to fix that firewall flex either. I had a customer with an early nova with a similar problem to yours; he had sent his shifter out to a rebuild specialist, tried different Z bars and clutches. It was simply a misadjusted clutch. I kept telling him this and he kept telling me he had adjusted it (I suppose properly is a different story LOL)

Good on you to get the bellhousing aligned and take a systematic approach to this. Sounds like a bitchin' ride; Got pics?

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Re: Doug Nash 4+1 hard to shift when hot

Post by GuysMonteSS » Tue Aug 25, 2015 4:22 pm

Here's a few pictures;
Image
Image
Image
The firewall flex is on my "to do" list.
It's good to know there are other options with bellhousings and clutch fork's but everything is working real good now so I will probably leave it |as is".
I sure am glad that I fixed this issue.
It was getting so I hated driving my car,now I love it :D
Thanks to everybody here for all the help !!
Guy
'86 Monte SS,513 BBC,AFR heads,Bullet solid roller cam,Doug Nash 4+1 5 speed,Hurst Inline Shifter,Ford 9 inch Rearend.

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