68 C10 Muncie M20 Project

[68 C10 Driver]

Ok, I know there are threads on here regarding Muncie 4 Speeds in Pre-72 C10s, but those all tend to go off tangent into folks suggesting going with a T10 or a S10 5 Speed.

Here is what I need help with. I already have the M20. I have the reverse switch set up and I have an aluminum bellhousing to go with the M20. What I need to know is who has done this and can you share any photos showing what you have done (i.e. issues with driveshafts, yokes, speedometer cables, etc.)

I plan on converting to a hydraulic clutch that will utilize a slave piston. I have seen the hydraulic throw-out bearings, but I think for now I will use the slave piston and standard throw-out bearing fork. I hate having to deal with stretched out cables and I think the hydraulic clutch will make it easier for my wife to drive the truck if need be.

I also plan on using a rear transmission support. I know some on the forum have stated that just letting it hang off the bellhousing is ok, but by going to the aluminum car bellhousing that isn't supported like the old one was, the rear tranny support just makes sense and will help stabilize things better.

Pictures will be a huge help if you have them. Especially showing a measurement from the firewall/floor seam to the opening for the shifter.

Speaking of shifter, I will be using a Hurst Competition Plus shifter with the shifter control made for a bench seat. Please see the attached photo.

[68 C10 Driver]

As my truck cab is currently set-up, the opening for the shifter is 10 1/4 inches from the firewall/floor seam. Attached photo is a look at how it is currently placed.

Just FYI, this truck looked to have what was a Muncie 3 speed, so I don't know if thinks will line-up just right, or if I need to correct things. The old transmission was old, it was a modification that my late father-in-law did when he switched from the column shift 25-30 years ago. I will retain the floor shift in his honor, just working to figure it all out. I have also attached photos of the old 3 speed with the Dexion shifter supports...really jury rigged, I want to do things right.

[firedemon]

thats not jury rigged thats the way those crappy conversion shifters came .dont throw it away theyre getting harder to find someone will buy it

[Grumpy old man]

This thread may help . What side is your speedometer on your tail shaft ? I'm using the early tailshaft with the speedometer on the drivers side and using a 70 inch metal cased cable from Classic , Also the truck shifter .

https://67-72chevytrucks.com/vboard/...d.php?t=814944

[68 C10 Driver]

The speedometer is on the passenger side of the transmission which will mean I will have to use a longer speedometer cable. I will probably see if I can find one about 84 inches or so to accommodate the bend needed to connect it with out binding it.

[Grumpy old man]

Consider watching all the Muncie videos on the 5speeds.com site , There is a lot of info there on the Driven brand gear oil comparison and magnetic plugs . I'm using the Driven gear oil in mine and in my Posi rear differential with additive ,

[68 C10 Driver]

Originally Posted by Grumpy old man

Consider watching all the Muncie videos on the 5speeds.com site , There is a lot of info there on the Driven brand gear oil comparison and magnetic plugs . I'm using the Driven gear oil in mine and in my Posi rear differential with additive ,

Have you been happy with this brand? What is the viscosity? How is the transmission noise?

Sorry for all the questions. I was going to go with any GL-4 85w90, but I am very open to recommendations, especially from those who are recommending what they are using and not just read about.

Thanks!!

[Bobbysgmc]

Use old school 85-90w.The newer gear lube will eat up your brass synchro's.Doing my swap next weekend weather permitting.Went with the M22 Rockcrusher with the correct gear ratio for 3.08 rear end.My shifter handle looks a lot like yours except home made.Good luck.

[68 C10 Driver]

Originally Posted by Bobbysgmc

Use old school 85-90w.The newer gear lube will eat up your brass synchro's.Doing my swap next weekend weather permitting.Went with the M22 Rockcrusher with the correct gear ratio for 3.08 rear end.My shifter handle looks a lot like yours except home made.Good luck.

Does there need to be an zinc additive put in along with the 85-90W?

Thanks for the input.

[68 C10 Driver]

Grumpy Old Man, I am with you on these trucks. I read one of your posts on Muncie Conversions (28 Nov 2020) about your philosophy in how you built your C10; I am trying to put mine together using parts that would have been available back in the day. To me, the whole point in having something like a 1968 C10 is the experience. I like having a vehicle I can work on without the aid of a $4000 laptop. To me the fun is being to show my kids (or those I would see at car shows) what the technology was "back in the day". If i want a vehicle that drives and runs like a new car/truck, I would buy a new car/truck.

It is the satisfaction of bringing back a piece of history, and since this truck has been in the family for quite a long time it definitely has some history.

[Furno68C20]

How about this gear oil

https://www.napaonline.com/en/p/FCA65205
Posted via Mobile Device

[Bobbysgmc]

I got my gear oil from Summit,made especially for older transmissions.

[Grumpy old man]

https://www.youtube.com/watch?v=Z7Np...4umMc&index=21
watch this video , Paul actually wrote the book on Muncie transmissions .


Description
The most basic gear oil offered by Driven, GL-4 protects yellow metals and provides proper synchronization to prevent clashing in synochronized manual transmissions. Containing high-quality base oils for high shear race protection and extended change intervals, it is recommended for any race or street performance application where GL-4 gear oil is required. Viscosity typcial of 80W-90.

[68 C10 Driver]

Originally Posted by Grumpy old man

https://www.youtube.com/watch?v=Z7Np...4umMc&index=21
watch this video , Paul actually wrote the book on Muncie transmissions .

Thanks! I will watch this first chance.

[68 C10 Driver]

Originally Posted by Furno68C20

How about this gear oil

https://www.napaonline.com/en/p/FCA65205
Posted via Mobile Device

Thanks, I appreciate the input!

[68 C10 Driver]

Originally Posted by Bobbysgmc

I got my gear oil from Summit,made especially for older transmissions.

I love this forum, I can't thank you all enough for the advice and willingness to help me on this project.