Guide bolts

[Doug&Deb]

I’m going to be pulling my M6 trans out of my Coronet. I understand the need for guide bolts for proper alignment. Can anyone tell me how long they need to be. I’m guessing slightly longer than the input shaft. If anyone has already done this I’d appreciate the help.

[Sam Buchanan]

7 minutes ago, Doug&Deb said:

I’m going to be pulling my M6 trans out of my Coronet. I understand the need for guide bolts for proper alignment. Can anyone tell me how long they need to be. I’m guessing slightly longer than the input shaft. If anyone has already done this I’d appreciate the help.

 

I don't know your transmission will compare with the one in my P15 but this is what works in my case. You can determine the length of the pins while you still have the trans in the car. See how long they can be without running into clearance problems and go from there. These are pretty much the maximum length that allows me to remove them once the trans is in place.

 

 

 

Edited April 15, 2023 by Sam Buchanan

[Doug&Deb]

Thanks Sam. I’ll take some measurements and go from there.

[Dodgeb4ya]

The dealerships used Miller Tool guide studs.

They are plenty long @ 3" .

Taperered at the ends and slotted to install and remove.

[soth122003]

Seems to me the big reason for the guides was to help line up the splines on the shaft with the clutch disc and to line up the shaft end with the pilot bearing without wresting with the tranny forever to get it installed. That being said 3-4 inches for the guide bolts should be a good length with out running into any clearance problems.

 

Joe Lee

[Dodgeb4ya]

I only use them on the M5/M6 heavy  transmissions.

[Sam Buchanan]

I use them because I'm afraid I might distort the clutch disc if the input shaft doesn't go in straight. They also hold the trans pretty much in alignment if the clutch disc needs to be fudged to get the splines to line up (I don't have the correct spline alignment tool).

[Doug&Deb]

For me it’s important that I not crack the carbon seal on the fluid coupling. Fortunately I work at a machine shop so we have plenty of bolts to modify.

[Dan Hiebert]

I imagine a transmission jack helps immensely, but I don't have one, so I made my own guide studs.   I measured how long the shoulder had to be to clear the transmission mounting holes and still provide enough room to allow for the input shaft and enough space to be able to pull them out when the tranny is set.  The shoulders happen to be 3" like the Miller Tool guide studs.  I ground a taper on the end but no slots or anything, I only finger tighten them in, and if need be, a pliers will loosen them up enough to pull out with ease.  It just so happens that those studs I made about 30 years ago also work on the several Fords I've worked on, and our Terraplane.

[Sam Buchanan]

Just for grins I measured the pins I made, was wondering how they compared to the genuine Miller pins. I ground flats so a 3/8" wrench could be used in case they tightened up with the trans slid into place. One of the long pins works best with the oil fill plug removed and the short one is the top driver bolt.

 

 

 

Just to show what shade-tree fiddlin' can do here the very crude cradle I use on the floor jack. This sorry looking contraption is strapped to the transmission and it usually works fine for lowering and raising the trans without a lot of drama or effort.

 

 

[greg g]

Looks very much like the one I cobbled up.

[Young Ed]

5 hours ago, Sam Buchanan said:

Just for grins I measured the pins I made, was wondering how they compared to the genuine Miller pins. I ground flats so a 3/8" wrench could be used in case they tightened up with the trans slid into place. One of the long pins works best with the oil fill plug removed and the short one is the top driver bolt.

 

 

 

Just to show what shade-tree fiddlin' can do here the very crude cradle I use on the floor jack. This sorry looking contraption is strapped to the transmission and it usually works fine for lowering and raising the trans without a lot of drama or effort.

 

 

I made a similar one out of steel from an old bed frame