Changing mainshaft length on 4 speeds, 48-77, bearing retainer plate screw removal

[docmel]

I got a smoking deal on a 1977 4 speed with a ratchet top. Of course the mainshaft in the '77 is the longer length for electric starter. I'm running a set up, '60 Pan, kick only. I have heard/read, that changing out the mainshaft for the shorter shaft, (AKA before HD had electric starts on BT's), is a direct swap of mainshafts only. I can confirm its true. Took about one hour. All gaskets/seals are interchangable as well. I wanted a short shaft tranny to avoid the clutter of a starter and bearing support for an open primary belt

Hardest part was the mainshaft bearing retainer plate on the kicker side, held on by 4 flatside screws. They have a habit if freezing in place, hard to remove. Of course penetrating oil is the key here. Once you get the kicker cover off, and the tranny top off and the counter gear cluster removed, sit the tranny on the kicker side end. Look inside the case and you can see the screw holes from the opposite side of the screw heads. Spray there, let gravity work it. In about an 2 hours I then could remove them. Tap them with a screw driver in the screw heads, not real hard, do it multiple times with each.......Be patient here, if you bugger these slot heads up, you have allot of work ahead

USE a factory manual when taking apart/reassembling the tranny. The pics and setups described inside really pay off

[CTNewman]

Impact screwdriver is a useful tool there. Just don't go ham and wail on it too hard.

[sidewindersigns]

I got a smoking deal on a 1977 4 speed with a ratchet top. Of course the mainshaft in the '77 is the longer length for electric starter. I'm running a set up, '60 Pan, kick only. I have heard/read, that changing out the mainshaft for the shorter shaft, (AKA before HD had electric starts on BT's), is a direct swap of mainshafts only. I can confirm its true. Took about one hour. All gaskets/seals are interchangable as well. I wanted a short shaft tranny to avoid the clutter of a starter and bearing support for an open primary belt

Hardest part was the mainshaft bearing retainer plate on the kicker side, held on by 4 flatside screws. They have a habit if freezing in place, hard to remove. Of course penetrating oil is the key here. Once you get the kicker cover off, and the tranny top off and the counter gear cluster removed, sit the tranny on the kicker side end. Look inside the case and you can see the screw holes from the opposite side of the screw heads. Spray there, let gravity work it. In about an 2 hours I then could remove them. Tap them with a screw driver in the screw heads, not real hard, do it multiple times with each.......Be patient here, if you bugger these slot heads up, you have allot of work ahead

USE a factory manual when taking apart/reassembling the tranny. The pics and setups described inside really pay off

I guess I don't see what the problem is with using the longer main shaft with a clutch setup that doesn't have a starter ring and just leaving off the starter? Why should you need to change the shaft?

[docmel]

I guess I don't see what the problem is with using the longer main shaft with a clutch setup that doesn't have a starter ring and just leaving off the starter? Why should you need to change the shaft?

The 65 to later BTs had a longer mainshaft (1/4" longer) for a few reasons.

You know the pre - 65, thin tin inner primary cover? That had to be changed for the 65 - later with electric start: The 65 - later inner primary cover had to be thicker to mount the selenoid, starter, as well as a inner primary cover mounted bearing support so that the longer mainshaft could take the stress.

So the 65 - later now had two mainshaft bearing supports: One inside the tranny case and one outside of the tranny, mounted inside the inner primary cover itself. There is your reason for the extra mainshaft length.

Even if I removed all starter related stuff, but kept the longer/later shaft, I would still have the run an external bearing support, more clutter than I would like, but easy enough if that was the case

The real issue is that with kick only, open belt, the tranny would sit to far to the left with the longer mainshaft, so the belt would not line up.

[toast]

This seems to be the place to ask... been hesitating on pulling the trigger on a transmission and primary for my 69 genny.

What I want to do is: kick only, enclosed belt primary (vented). Which shaft length ratchet top and inner/outer primary do I need to match this all up to a 1.5" belt?

[Dragstews]

To add a bit more tech to this thread ....

The 36 to 54 used a 1" tapper keyed motor sprocket shaft, in 55 that was changed to a 1-1/4 splined shaft, but keeping the same aliment from trans to motor...
In 65 (To 69) a ele. starrter was added which required a bit more room. 3/8" was added to both the motor and trans mainshaft.
Then in 1970 the alternator was added.... More room was needed to make that work... Again the motor sprocket shaft and trans mainshaft got longer...

For a little more info about the mainshafts is the rear belt drive models of the later runs for the Shovels... It's the grand-daddy of all the mainshafts... It's even longer than the 70-up chain drive models...



_________________________________________________

Been hesitating on pulling the trigger on a transmission and primary for my 69 genny.

What I want to do is: kick only, enclosed belt primary (vented). Which shaft length ratchet top and inner/outer primary do I need to match this all up to a 1.5" belt?

There are a few ways you can go about doing this....

One is to keep the OG inner primary for 65-69 ....





And use block-off plates for the ele. starter holes...

The other way is a bit more trick...



Chrome steel inner primary cover for Big Twin models.
Fits: FL 1965-1969

And run a tin outer cover of your liking...

[inkaddict92]

So let me get this straight. I have a 79' shovelhead engine, 1980 cowpie tranny, and a custom frame built with pan specs to run a mechanical brake. For me to get everything to line up I would just have to swap the mainshaft to an earlier 1937-64 shaft?

[docmel]

So let me get this straight. I have a 79' shovelhead engine, 1980 cowpie tranny, and a custom frame built with pan specs to run a mechanical brake. For me to get everything to line up I would just have to swap the mainshaft to an earlier 1937-64 shaft?

Man, years (decades) ago I was a master at this. For example, I have run BT evos in pan rigid frames, with after '65 trannies, with a short mainshaft installed so i could run a KS start only and open belt drives with no internal primary for cleaner look. Changing out mainshafts was the way to go, dependent on what year tranny I had laying around at the time that I could use

When the BT evo first came out, there was allot of folks, at least in my crowd, that wanted to run the new evos in shovel or pan frames that were available at the time. At that time, folks wanted EVO BTs because frankly, you didnt need to do much wrenching, and one could jam 500 miles one way to a party on a friday, and come back on a Sunday w/o any real worries. Believe it or not, at that time, except for a certain percentage of us, the whole nostalgia thing with pans and shovels wasn't all that big during that time.

I would take shovel or pan frames, clearance the rear rocker box area, and bolt a BT evo motor right in, and take whatever tranny I had and switched out the mainshaft if all i wanted was a kick start and open belt drive

Ok, back to your question: There is no doubt that I have taken a cow top, (made for an e start), and converted it over to a short shaft and KS only, by changing over to a pre 65 main shaft. But there are some other issues that I remember: Ok, so: Regardless if it was a Pan, Shovel or EVO BT motor

1. I did run into some tranny top clearance issues on some OEM frames, as far as the clearance between the top of the tranny and the stock oil tank. It depended what year/model frame it was. On chopper frames, I dont beleive I ever had an issue with oil tank clearance

2. The cow tops had some weird and small internal variants thru the years. I wish i could say that all years of them would only require swapping out the mainshaft and new set of gaskets. But i cant for say sure






shovels and pans werent

[inkaddict92]

Thanks a lot for the info Doc and Dragstews !

I've got my 1980 4 speed completely stripped to the case right now and I'm at the stage where I just need to order the parts for the rebuild. The kicker side including the cover itself were all definitely a pain in the ass to take a part. Kicker gears were jammed in there because of a bushing that was destroyed, but I was able to get it all out with a small gear puller. The stuck oil slinger also messed with the kicker cover clearance, so I had to pull each stud out to remove the cover.

Just curious too, isn't the clutch pushrod longer for the newer 4 speeds as well as having a different oil slinger? None of this is affected in the mainshaft swap?

[docmel]

If you are talking the oil slinger in the kick cover: There are two types of TO bearing in the KS cover for the older trannies, to include yours. The old "Bell" type, and the newer "snowflake" wafer. Both CAN work with the same oil slinger, but I have found that some aftermarket kick covers will not clear the bell type TO bearings. As far as the clutch PR goes, yes, be sure you get the right length. I have taken the longer style and just turned it down on one end to work. The od is the the same, so no probs there

[docmel]

If you are talking the oil slinger in the kick cover: There are two types of TO bearing in the KS cover for the older trannies, to include yours. The old "Bell" type, and the newer "snowflake" wafer. Both CAN work with the same oil slinger, but I have found that some aftermarket kick covers will not clear the bell type TO bearings. As far as the clutch PR goes, yes, be sure you get the right length. I have taken the longer style and just turned it down on one end to work. The od is the the same, so no probs there

Sorry, my bad: The older bell shaped TO bearing doesnt need the slinger: The bell design serves as a slinger. You need the slinger for the newer wafer style TO bearing

[inkaddict92]

Sorry, my bad: The older bell shaped TO bearing doesnt need the slinger: The bell design serves as a slinger. You need the slinger for the newer wafer style TO bearing

Alright thanks I was actually wondering this because when I took apart the 1980 tranny I bought, it had the earlier bell style bearing in there and now I realize that's why I had such a problem removing the kicker cover due to clearance with that bearing.

[docmel]

Yeah, good point. The old style bell type bearing is an odd fit when trying to put the kicker cover back on the tranny, even with the proper OEM kicker cover. It has to fit just right on the end of the pushrod, while at the same time sliding the slot on the bell into the clutch finger release thingy. And its a tight fit in there with TO bearing, just as you are describing

There are allot of folks the get the newer wafer style (me included), to replace the bell type TO. Its allot easier to get the kicker cover back on, more clearance, and you dont have to finagle the fit

[inkaddict92]

yeah, I ordered all the parts today and made sure I got the newer wafer style part and shorter pushrod to account for the shorter mainshaft. This thread helped out a lot because I was literally scratching my head staring at my tranny torn down to the case wondering about that mainshaft swap. Thanks a lot doc