Which overdrive transmission would be easier to install?

[vetnat]

Hi. Trans would be going into a 1961 c10, hopefully behind a 292 eventually, but currently behind a 235. I think the 7 bolt side cover Saginaw O/D is a more desirable transmission, but would a 4 bolt side cover Muncie O/D transmission be an easier fit, since it more closely resembles the three speed trans that is there now? From searches, it appears some people did not have to modify their shift linkages, drive shaft, etc, and some people did. Would either O/D transmission require some modifications, or are they bolt in? Looking at a 7 bolt Saginaw O/D, from a 1968 Chevelle apparently. Thanks.

[Chevy Fleetside]

I put a 3 speed OD in my 65. The trans is 5 1/2" longer then the 3 speed so I had to have the drive shaft shortened. All I had to use was my old side cover from my original trans so no mods on shift linkage.

[vetnat]

OK, worked a 14 hour day, then got called back in to work for an emergency at 2AM, and I'm now sitting up at 4AM too wired to sleep. So, I'm saying my mental capacity isn't much right now

So, I am thinking of buying a 7 bolt overdrive transmission (Saginaw) supposedly out of a 1968 Chevelle. From what I can tell, a 7 bolt trans should be a bolt in replacement for the 4 bolt Muncie currently in my truck. So, does it follow that a 7 bolt overdrive trans will also be a bolt in replacement? And being that the trans is from a car, does that complicate things? I've read that some rear mounting holes are not tapped on the car trans, sounds like not a big deal. But I also read that the front bearing retainer is different sizes between car and truck transmissions. Does this require any mods? These overdrive transmissions are not cheap, so I'm trying to make sure the one I'm looking at will work before I pull the trigger. Thanks again.

[geezer#99]

I don’t recall any o/d tranny from a 68 Chevelle.
You got a link or picture of one.
Only 7 bolt cover would be a full synchro 3
speed.
Educate me!

[61K10]

Good trans. Will bolt right up to your bell-housing. Bearing retainer is the same if from a car and a 67 tk. I think 68 up tks had the bigger bearing retainer. Drive shaft will need to be shortened as the trans is longer. (same length as the 4bolt o/d) the d/s yoke will need to be changed to a fine spline one. Same as late t350 trans. the shifting linkage will need some work. Try doing a search as some have done this swap.

[ray_mcavoy]

We swapped a 3-speed OD trans into Dad's 66 last winter. The old 3-speed we took out was the non-synchro 1st with the 4-bolt side cover and the OD trans that went in was the full-synchro with the 7-bolt side cover. And everything that 61K10 listed is correct.

The trans we swapped into Dad's truck originally came from a car so the two lower mounting ears (that attach it to the bellhousing) were not threaded like they are on a truck trans. We simply used a couple of longer bolts (with nuts inside the bellhousing and accessible with the lower inspection plate removed) to deal with that minor issue.

The two shift levers (on the side of the trans) are different for car vs. truck applications too. So we swapped those out with some levers that came off a 67-72 style truck that originally had the 7-bolt side cover 3-speed. That allowed the existing 2nd/3rd shift linkage rod to be re-used without any modifications. But the 1st/rev lever is farther back on the 7-bolt side cover so I had to cut and weld an extension into the 1st/rev linkage rod like Sizemore 65 shows in this post --> http://www.67-72chevytrucks.com/vboa...d.php?t=711857 That 1st/rev linkage rod also had to be re-bent slightly to keep it from hitting the outer end of the clutch fork.

[vetnat]

Thanks so much for the replies everyone. I'm trying to make a deal while totally fried from the hours at work, so I really appreciate not having to "try" and think the details through by myself. These suckers aren't cheap, but the deal I'm trying to get through isn't bad. Its from a junkyard, talked to the guy today, he said he actually didn't know what kind of car its out of, they bought it in a lot of assorted parts. 1968 passenger car is the best he could come up with. I'll post pics soon. He sent me some more pics today. Turns out the solenoid (or is it the governor?, too fried to figure it out right now), is totally coated in silicone, so I'm guessing there was a leak So, I will assume that piece is non-functional, and I will have to source another. Trans is in Minnesota, but the shipping charges are quite reasonable.

[vetnat]

So far I'm understanding that the 4 bolt and the 7 bolt overdrive transmissions are the same length, so both require shortening of the existing driveshaft. I've never done any driveshaft work before. Easy enough to do with 1 person? Anybody have a ballpark figure for the cost? Can this be done at a machine shop, or does it have to be done at a driveline shop?

My truck is a 1961, so the front bearing retainer should be same size as a car trans. Non-tapped holes for mounting, sounds easy to overcome. Need a different yoke, but sounds like a common one.

And then can likely use some shift linkage rods off a 67up truck with the 7 bolt trans, and some mods to existing rod. Clutch fork is on passenger side in my truck, so shouldn't be interference there. This is such a fantastic help! Thanks again.

[vetnat]

Ok, trying to read for comprehension Looks like shift levers need to be from a 67up truck, and I can reuse my current shift rods, with some mods.

[vetnat]

Some pics of the trans.

[vetnat]

If I instead found a 4 bolt O/D trans, I guess I could reuse my current side cover and shift levers. Something to think about.

So, other than the fact that the 7 bolt is a full synchro, and the 4 bolt has non-synchro 1st gear (which I hear doesn't matter much with the O/D), are they otherwise pretty equal in "desirability"?

[CRUZN66]

Originally Posted by vetnat

If I instead found a 4 bolt O/D trans, I guess I could reuse my current side cover and shift levers. Something to think about.

So, other than the fact that the 7 bolt is a full synchro, and the 4 bolt has non-synchro 1st gear (which I hear doesn't matter much with the O/D), are they otherwise pretty equal in "desirability"?

Word of caution, first I bought a used muncie 319 (4 bolt) from a shop in Kansas City for $675 and thought it was a good deal. WRONG, ended up being the only parts that were good was the case and the shop would not stand behind it RIPPED OFF!

So then I found out about Gary Bernard of AAAA Transmissions in Fort Worth, TX and called him and we chatted. He ended up building me one from scratch out of all the parts he has accumulated over the years then shipped it to me. It works like a champ and bolted straight in with the existing linkage, just wish I would have got a hold of Gary first would have saved a bunch of $$$$$.

Rope

[61K10]

Don't know what all the silicone is about. Maybe water was getting in it. It has a yoke already stuck in it. For the drive shaft if you could find one out of a power-glide (auto trans) it might be the right length?

[ray_mcavoy]

Originally Posted by vetnat

So far I'm understanding that the 4 bolt and the 7 bolt overdrive transmissions are the same length, so both require shortening of the existing driveshaft. I've never done any driveshaft work before. Easy enough to do with 1 person? Anybody have a ballpark figure for the cost? Can this be done at a machine shop, or does it have to be done at a driveline shop?

Yes, both the 4-bolt & 7-bolt overdrive transmissions are the same length. I believe the non-overdrive 7-bolt 3-speeds are the same length too. Most of the 4-bolt 3-speeds are shorter but I think there were a few applications that used a long tailshaft. If yours is the long tail version, there is a good chance you will be able to re-use the existing driveshaft.

Dad had a local driveline shop make a completely new driveshaft for his truck (shortbed with a 1-piece shaft). I don't recall the exact price but think it was under $200.

Originally Posted by vetnat

And then can likely use some shift linkage rods off a 67up truck with the 7 bolt trans, and some mods to existing rod. Clutch fork is on passenger side in my truck, so shouldn't be interference there.

The parts you need off a 67up truck are the two shift levers (not rods) that bolt to the shafts on the side of the trans. I think some 67 (and possibly 68) trucks were still using the 4-bolt side cover 3-speeds so your best bet for finding the ones off a 7-bolt side cover trans would be in the 69-72 year range. Don't even bother looking at the 73-up trucks ... the 3-speed shift levers in those are different and won't work (they look similar to the car ones).

I forgot about your clutch being hydraulic with the fork on the passenger side ... that should eliminate any clearance issues there. So the only modification would be welding an extension into the 1st/rev rod so it reaches the location that's farther back on the 7-bolt trans.

Originally Posted by vetnat

He sent me some more pics today. Turns out the solenoid (or is it the governor?, too fried to figure it out right now), is totally coated in silicone, so I'm guessing there was a leak So, I will assume that piece is non-functional, and I will have to source another.

Yes, looking at your pics, that is the solenoid that someone coated with silicone. Kind of makes you wonder if (like 61K10 said) they had issues with water getting inside so hopefully the innards aren't all rusty & corroded.

The solenoids are different for the overdrives with the 4-bolt vs. 7-bolt side cover. The solenoid used in the 7-bolt trans has a longer shaft and from what I have seen, replacements are very hard to find. So if the seller can test it and verify that it still works, that would be a plus.