Help with Mr Gasket 7667 3-Speed Shifter Rebuild

[dbrannon79]

Hey guys, working on my son's 68 Chevy C10. the 3 speed manual trans has a Mr Gasket brand part number 7667 floor shifter installed. these are NLA as far as I can tell. replacing it with a Hurst equivalent is expensive. The shifter has gotten sloppy and the center arm locating pin will slip between the two shift lever arms unless you hold pressure left or right on the shifter during every movement. I am thinking that there are some sort of shims or bushing inside it that might need to be replaced. wondering if anyone has some experience with them.

I found a couple of youtube videos that explain how to install and adjust the linkage, they do a good job showing how the shifter works, I will look for them and post the links.

 

[dbrannon79]

Here is the install video. it's a good detailed one. starting at time stamp 20:53 shows in detail how it works with the center locating pin. the locating pin is supposed to stay in the 2-3 shift lever and can be pushed over to the 1-R lever which is under spring action. on this one the spring is intact and works, but when you are in 1st and let go of the shifter there is enough slop that allows the locating pin to come out of the 1-R lever where when you go to shift into 2nd the lever will stay in 1st and try to jam gears. only way to avoid this is you have to reapply pressure on the shifter to the left and hunt for the pin to fall back into the 1-R lever before following the H pattern into 2nd..

I can reach underneath and move both of the levers side to side some which is enough play I think that is allowing the locating pin to come out while in gear.


starting at time stamp 20:53 shows in detail how it works with the center locating pin.

 

[MrMarty51]

I thinking a nice four speed transmission with overdrive would do this truck a lot of good.

 

[dbrannon79]

Agreed! The PO gave him a (can't remember if 4 or 5 speed) getrag trans for it (looks alot like an NV3500). But to install that, we would need to shorten the driveshaft. He just wants to get it to the point he can learn to drive stick. I told him he can drive it as is now, just keep a hammer in the tool box for the gears and lets get out there and grind some gears LOL.

I will post some photos of it maybe we can truly identify what it is

 

[dbrannon79]

I just went out and got the cast numbers off the trans he gave him. GM 23049844 on the bell housing and GM 23049617 main body. according to the innerweb the 23049844 is a getrag 5 speed NV3500. grabbed a pipe I had to fit over the shifter knub and went through each gear turning the input shaft by hand. it's indeed a 5 speed trans.

the left bottom bolt hole is broken off the bell housing but I think I can still run it as it is like that. still has a little area for a flat washer to grab hold of if I place something on the broken area with the same thickness.

Hmmm... wonder what else he would need for the swap from the three speed. wonder if the clutch has the same center splines to fit the input shaft and if the fork will work with the linkage without needing to convert to hydraulic. we have the cross member. also does the driveshaft use the same splined yolk for the output shaft even though it will need to be shortened.

it uses a electronic speed sensor where the 3 speed has a cable driven speedo. he would need something to convert the speedo to electronic or the sensor spot to use a cable. maybe we should jump to do the trans swap vs trying to fix the shifter on the 3 speed?

 

[dbrannon79]

He would be going from ...

SM-326 1st=3.50, 2nd=1.89, 3rd=1.00
to
NV3500 1st=4.02, 2nd=2.32, 3rd=1.40, 4th=1.00, 5th=0.73

I have no idea what the rear end gears are, I would assume they are 4:10 or 4:11 gears. what do they normally come with in these trucks? C10 single cab with 8 ft bed and 250 l6 engine.

much smoother takeoff and overdrive. I would be jealous LOL

 

[dbrannon79]

Well after doing some reading, a hydraulic slave and master would be needed and remove the manual clutch linkage. that might be a no go. 1 he wants to keep it as original as possible and 2, it might prove to be more trouble than I want to dive into right now. there are kits available, but they are expensive and involve cutting holes in the firewall and then some.

So.... back to trying to fix the sloppy shifter and maybe later looking for a different trans that can use the factory mechanical clutch. something that would be more of a direct swap that a lot of aftermarket modifications. I'm sure I could figure out a way to do a hydraulic clutch swap and use the z bar for the master cylinder with a remote fluid res or a bracket to use some of the linkage keeping from cutting into the firewall. even if I do the swap, it will also come down to part store available parts and trying to match a slave and master that works together too.