Transmission mount confusion

[MileHiSS]

Work continues on my 62 Biscayne restoration, and in reading the AIM I find a conflict on the transmission mount.

My plan was to install the crossmember in the upper set of holes per Section 2 sheet 2.00

Section 313 Sheet 3.00 makes note that the "Transmission mounting crossmemeber to be assembled in lower holes"

Which is correct? What am I missing here?
http://pic20.picturetrail.com/VOL97/466970/8521984/227530737.jpg
http://pic20.picturetrail.com/VOL97/466970/8521984/235212571.jpg

[W Head]

What type of transmission are you installing, 4-speed, p/g, tubo 350, ect.????

W Head

59 El Camino 348-3,2s
59 Impala 409-2,4s

[MileHiSS]

I'm going to use a non stock Muncie M-22

On further reading

Section 685 sheet 100...... lower holes for a 4 speed (Borg Warner? pre Muncie)

Now I'm really confused:dunno

[oldskydog]

It is confusing the way it is shown. I don't have a 62 AIM but checking the 61 and 64 shows that the upper holes are for the standard 3 speed trans and the lower holes are for powerglide, overdrive and 4 speed. This can be confirmed in the service manual under transmission installion procedures.:scratch

[Ronnie Russell]

This is a funny subject. I have always used the lower holes. A buddy e-mailed me a page from GM assembly manual that states upper for 4 speed. Which GM book do you believe??:rofl :rofl Personally, I would use the lowers, but I guess you can't go wrong!!!

[jester]

I would measure the degree angle of the trans to front shaft. what ever combo left me with the closet to the specks in the manual would be my choose. Just my thoughts.:rofl :rofl

[58impala]

I agree with jester...........the reason for the two sets of holes is to bring the driveshaft angles into specs with the different OEM transmissions. Check the shop manual for details on how to adjust these angles (three adjustment points). Pick the correct hole for the least amount of shims for the correct angle. Otherwise you will have vibration at varing speeds and U joints wont last very long. If you don't have a shop manual contact "Inland Empire Drivelines" and ask for a free brochure on how to correctly adjust driveline angles.

[oldskydog]

Like Jim says, it is for the driveshaft angle-and the factory did part of the work for you. In the 64 AIM( I think it's in section 9) there is a diagram and chart showing the driveshaft angle and shimming procedure specifying that the distance you are trying to achieve between the driveshaft centerline and the transmission support is 2.38" on the 3 speed and 3.38" on the PG, and OD. If you think about the difference the length of the transmission makes in the angle it makes sense. There is a note that the upper holes are used for all but the powerglide and overdrive and the lower holes are for all but the 3 spd. The 4 speed is not mentioned but it is about the same length as the overdrive while the 3 speed is a shorty. Also in the RPO for the 4 speed option it specifies that the lower holes are used. Again in the Service Manual transmission installation procedures it specifies the proper hole to use for each transmission.
The upper or lower holes are a starting point for the driveline angle shimming and is obviously based on the length of the transmission.

[MileHiSS]

Well, thanks, I'm going for the lower mount. I have to shorten my driveshaft before I can check my pinion and driveshaft angles.

[jim_ss409]

It's been a while since I did mine but I'm with the other guys, I'm almost positive that you use the lower set of holes. I'll poke my head under the car to double check tomorow.
By the way, the frame looks great!:beerbang