Swapping the SM465 for a Car style 4 speed

[794spdcustom]

Good Morning all;

I have a 79 big ten custom with the 465 Muncie 4 speed. I am going to swap out for a car style 4 speed for more cruising functionality and fun factor. I will be rebuilding the stock tired 350 with a goal of right around 300 HP. I'm sure this has been done many times and was hoping to gather some info before moving forward to hopefully avoid missing anything important.

I have a Saginaw four speed from probably a late 70,s early 80's Camaro I believe which is in really nice condition, and was more in my price range than the Muncie's and T-10S So my questions would be:
1) Will the crossmember fit the different style Transmission?
2) Will the existing driveshaft be the right size/length?
3) I have heard the tunnels are fairly easily replace as they bolted in? This was the first I had heard of this.
4) Will the clutch linkage be the same/useable?

Any other pertinent info on doing this swap would be greatly appreciated.

Many Thanks

Brad

 

[DoubleDingo]

I would discourage you from doing the swap to non-truck transmission. But it is your truck. Something to keep in mind is the rear end gear ratio. If it is too high, taking off in 1st will need a lot of clutch slipping to get it going. You won't be able to haul stuff like you can with the SM465. You won't gain any miles per gallon benefit, as each transmission will be 1:1 in 4th gear. I may be wrong here, but I don't think there is a cross member on the back of the SM465. Then again, I have never owned a 2wd square with the SM465, only 4x4. I do know the older vehicles just let the transmission hang off the bellhousing with the transmission mount, and the cross member was only for e-brake. The driveshaft will need to be altered and you'll need a yoke for the Saginaw 4 speed. The tunnel will be just fine to clear the Saginaw, but I don't know if you'll have shifter issues with the hump being higher. Clutch and linkage is for the clutch, not the transmission.

If it were me, I would leave it alone, as the SM465 is a great transmission, and to me, shifts just fine.

 

[794spdcustom]

Double Dingo;

Thanks for the input, The truck is as much for cruising as it is for any type of work detail. I find the only thing about it that bothers me is the 465. Its cumbersome and really just a three speed with an unusable first gear unless your pulling stumps or something similar. I believe this truck has 3:08 s out back with an open diff.
I have a buddy whos put the same tranny (saginaw)in place of an auto and just loves it. I knew there would be some issues or extra work to do which I am prepared to do. Having said that the tunnel seems to be quite different from the 465 (top loader tranny) to the saginaw, muncie and T-10 so I was hoping to change that in hopes of making it at least look stockish.

The 465 is a tough transmission but horrible for every day driving IMO, but I appreciate your input.

 

[idahovette]

The high tunnel. the drive shaft, and shifter placement will be the biggest points, I think. The crossmember will need to be relocated, but this isn't gonna be rocket science for any of this??

 

[SquareRoot]

Put in a nv3500, then you got overdrive too boot. No matter what combination you end up with youre milage is gonna still suck. It is what it is.

 

[Nonstop]

You will also need the bellhousing. The 465 has a larger register for the input bearing retainer.

 

[DoubleDingo]

Double Dingo;

Thanks for the input, The truck is as much for cruising as it is for any type of work detail. I find the only thing about it that bothers me is the 465. Its cumbersome and really just a three speed with an unusable first gear unless your pulling stumps or something similar. I believe this truck has 3:08 s out back with an open diff.
I have a buddy whos put the same tranny (saginaw)in place of an auto and just loves it. I knew there would be some issues or extra work to do which I am prepared to do. Having said that the tunnel seems to be quite different from the 465 (top loader tranny) to the saginaw, muncie and T-10 so I was hoping to change that in hopes of making it at least look stockish.

The 465 is a tough transmission but horrible for every day driving IMO, but I appreciate your input.

Just be aware you'll be doing a gear change too. 3.08 with the high 1st gear ratio of those 4 speeds, and you'll be slipping the clutch big time at each stop. The tunnels are higher for the heavy duty 4 speeds, as compared to the automatics or 3 speeds. Personally I like the heavy duty 4 speeds, you have your normal driving gears (2nd-3rd-4th) with one less shift than a 4 speed, and your stump pulling 1st gear as well.

 

[Ricko1966]

I bought a truck as a 17 year old kid. 1970 4x4 but running 2wd with a muncie 4speed from a car and no transfer case. 350, double humps, ..510 x 292 cam, a torker, Holley and headers.That truck was a blast to drive.

If memory serves me right the Saginaw 4speed shifter bolted to the tail shaft housing with a 3 bolt bracket make a riser for the bracket out of a piece of plate aluminum or steel.Depending on how you make the bracket you can come up, forward back or even right to left.Saginaw 4speed should be same length and spline as th350 3/4 inch shorter than 700r4 so grab cross member and drive shaft for a th350 square, 700 would work but just not as right. Bellbhousing clutch and flywheel from the Camaro This is all from memory so do some checking, but pretty sure this is right. Also the. Saginaws had grooves cut in the main shaft to identify 1st gear ratio not all had the same 1st gear.If you dump the clutch on that Saginaw very often you will need another Saginaw.

 

[bucket]

I've got a Saginaw 4 speed that I want to use in my truck too. It's a 2wd shortbed and I don't use it for hauling or towing. Just a fun street cruiser with a big block. I know for sure it would be a lot of fun, at least for a little while until it breaks.

I thought there was an aftermarket input bearing retainer available to fit the larger opening of a truck bellhousing? Does anybody know what I'm talking about?

 

[idahovette]

Somebody, I can't recall who, makes a circular adapter so you can use the bigger opening pickup bellhousing. I'll see if I can find it in my files, tomorrow(today?) Also,, I really don't think you would have to change gearing, about 70 percent of most 4 speed cars, Chevelles, Novas, Camaros, etc all had 3.08 or 3.31-3.36 gears from the factory. Not a lot of clutch problems that I remember. You can't beat on a Saginaw like you can a Muncie or Borg, but it will hold up if you are kinda careful!! @Ricko1966 is right about the shifter, you can fab a lever to work for it.

 

[75gmck25]

I had a ‘69 Torino Cobra (428 CJ engine) and with the 2.32 low 4 speed and F70-14 tires (about 26” diameter) they recommended 3.91 gears for the street. With the 351 engine in the GT they used the 2.78 low gear 4 speed to improve off the line performance.

Based on that very small data point, you will need lower gears if you want snappy performance on the street with a car 4 speed in your truck. And you would want a Saginaw with a low 1st gear ( some apparently go as low as 3.50) if you can find one.

Bruce

 

[idahovette]

Advance Adapter has a bushing (reducer) # 716078. $26.20 in Summit ads.

 

[DoubleDingo]

Somebody, I can't recall who, makes a circular adapter so you can use the bigger opening pickup bellhousing. I'll see if I can find it in my files, tomorrow(today?) Also,, I really don't think you would have to change gearing, about 70 percent of most 4 speed cars, Chevelles, Novas, Camaros, etc all had 3.08 or 3.31-3.36 gears from the factory. Not a lot of clutch problems that I remember. You can't beat on a Saginaw like you can a Muncie or Borg, but it will hold up if you are kinda careful!! @Ricko1966 is right about the shifter, you can fab a lever to work for it.

I believe those had first gears, and 2nd-3rd gear sets to match the rear end gears. I have seen the info, but I cannot recall where I saw it.

 

[DoubleDingo]

I had a ‘69 Torino Cobra (428 CJ engine) and with the 2.32 low 4 speed and F70-14 tires (about 26” diameter) they recommended 3.91 gears for the street. With the 351 engine in the GT they used the 2.78 low gear 4 speed to improve off the line performance.

Based on that very small data point, you will need lower gears if you want snappy performance on the street with a car 4 speed in your truck. And you would want a Saginaw with a low 1st gear ( some apparently go as low as 3.50) if you can find one.

Bruce

....if you can find one...that is the kicker.

 

[Ricko1966]

Also the. Saginaws had grooves cut in the main shaft to identify 1st gear ratio not all had the same 1st gear.If you dump the clutch on that Saginaw very often you will need another Saginaw.

4 different 1st gear ratios available. No groove is like 2.5 first 1 groove like 2.85 first 2 groove like 3.11 1st 3 groove was like 3.5 first. For low horsepower junk I used to look for 2 grooves I don't remember this ratios for sure but I know I'm close