AA Style Propeller Mount Advice (1 Viewer)

[ijonesinsp]

Has anyone ever had any experiences with this style of transfer case mount causing excessive stress to the original housing? I have heard there have been issues now and again with the aluminum housing, but I need to have some kind of mount in the rear to minimize the side to side movement. I will be running a 350 Chevy with a mild cam, SM420 and original 4 speed transfer case with the t-case saver plate. I am just considering what other options I would have for a rear crossmember if I didn't go this route. I will have the two motor mounts on the engine and two on the bell housing as well. Sample picture:

 

[B y r o n]

Been running one for years. Originally it was factory 3 SPD behind built 350, installed in the mid 80's. When I upgraded the trans to NV4500 I also added case saver parts on the transfer case. Everything is still in one piece and no issues.

 

[4x4veteran]

Similar story as Byron, installed in 84, still using, no issues.

 

[ijonesinsp]

Thanks for your input! Much appreciated.

 

[peesalot]

I have your same exact set up for 20 + years. FWIW setting all 6 is tricky. The mid mounts on the bell housing will work loose periodically and if the rear bushings are not right or fail it can cause the ears on the bell house to break, not the end of the world. Set the motor, bolt everything up out back use washers/spacers to get the right height on the propeller mount for your shifter and e-barke clearance on skid plate, then set the bell house mounts with appropriate washers/spacers. You dont want the bell house mounts to high thats why set the rear first. use studs at rear of tcase with loc-tite. Look at the tcase side of the AA prop mount where the rear cone is. There is a weep hole on the OEM cone cover that is not mimicked on the AA mount. That causes oil build up in the cone and subsequent leaking. Take a dremmel and re create that oil passage you see on the OEM cone cover. When you get it all up in there leave the prop mount wings unbolted, slide onto studs with a good, even coat of grey gasket maker/silicone on a clean/dry tcase, dont use so much it blocks the oil passage you created, let it set up, mount prop mount to tcase, tighten, then see where the wings line up, raise or lower tcase to clear shifter and skid, high as you can, the driver side nut or bolt head will be stuffed up against body support, its tight but doable, set bushings with spacers so tcase is at the desired height. FWIW you will want to trim the pass side frame tab for the propeller mount off right at the edge of big hole, this will let you install and remove tcase much easier, ask me how I know. It is important to mount to tcase first then wings and the weep hole is important IMO. After all that you move onto bell house mounts, I bolt the tabs to the bell house then stack a bushing, if the stock bushing is too tall cut to fit, if to short add washers. Let all the weight rest on the rear propeller mounts when setting the bell house mounts.

 

[ijonesinsp]

I have your same exact set up for 20 + years. FWIW setting all 6 is tricky. The mid mounts on the bell housing will work loose periodically and if the rear bushings are not right or fail it can cause the ears on the bell house to break, not the end of the world. Set the motor, bolt everything up out back use washers/spacers to get the right height on the propeller mount for your shifter and e-barke clearance on skid plate, then set the bell house mounts with appropriate washers/spacers. You dont want the bell house mounts to high thats why set the rear first. use studs at rear of tcase with loc-tite. Look at the tcase side of the AA prop mount where the rear cone is. There is a weep hole on the OEM cone cover that is not mimicked on the AA mount. That causes oil build up in the cone and subsequent leaking. Take a dremmel and re create that oil passage you see on the OEM cone cover. When you get it all up in there leave the prop mount wings unbolted, slide onto studs with a good, even coat of grey gasket maker/silicone on a clean/dry tcase, dont use so much it blocks the oil passage you created, let it set up, mount prop mount to tcase, tighten, then see where the wings line up, raise or lower tcase to clear shifter and skid, high as you can, the driver side nut or bolt head will be stuffed up against body support, its tight but doable, set bushings with spacers so tcase is at the desired height. FWIW you will want to trim the pass side frame tab for the propeller mount off right at the edge of big hole, this will let you install and remove tcase much easier, ask me how I know. It is important to mount to tcase first then wings and the weep hole is important IMO. After all that you move onto bell house mounts, I bolt the tabs to the bell house then stack a bushing, if the stock bushing is too tall cut to fit, if to short add washers. Let all the weight rest on the rear propeller mounts when setting the bell house mounts.

Great advice, thanks. Would you mind posting a picture of trimming the passenger side frame tab? I'm having a little trouble envisioning what your describing.

 

[peesalot]

Once you place the frame side tab on pass side, the horizontal part of tab, or shelf if you will, protrudes from frame toward center and has a large hole which the bushing has a shouldered index part that fits in big hole, the remaining portion of tab that extends beyond hole toward center needs to be removed, I left a thin , 1/8 " , portion, you could even cut into the hole a bit. It allows you to push/pull the tcase on and off the trans outputshaft without cussing.

 

[ijonesinsp]

Once you place the frame side tab on pass side, the horizontal part of tab, or shelf if you will, protrudes from frame toward center and has a large hole which the bushing has a shouldered index part that fits in big hole, the remaining portion of tab that extends beyond hole toward center needs to be removed, I left a thin , 1/8 " , portion, you could even cut into the hole a bit. It allows you to push/pull the tcase on and off the trans outputshaft without cussing.

Gotcha

 

[Downey]

Know that using this mount does not stress the transfer-case, the case keeps it's strength, the mount keeps it's strength, then when you bolt the two together they support each other making each other stronger- - -very simple engineering theory.

 

[pb4ugo]

Yrs ago when I ran a sbc, stk 4speed/tcase I split several stk tcases in 1/2. None of them were becuase of the propeller crossmember. It has more to do with the offset rear output. I would support the driveline from the frt and rear propeller crossmember. I think a 3rd support in the center could put the drivetrain in a bind. Imo, It would be hard to get even support thru out all 3 mounts.

 

[ijonesinsp]

Yrs ago when I ran a sbc, stk 4speed/tcase I split several stk tcases in 1/2. None of them were becuase of the propeller crossmember. It has more to do with the offset rear output. I would support the driveline from the frt and rear propeller crossmember. I think a 3rd support in the center could put the drivetrain in a bind. Imo, It would be hard to get even support thru out all 3 mounts.

Yea from what I understand, it’s the offset output causing heavy lateral deflection under load that stresses the case. I think between not allowing it to move by using the propeller mount and the case saver bracing the torsional stresses, it should be a pretty solid setup. The engine I’m putting in is no heavy hitter, but it will have a good amount of low end torque. Thanks again for all the input guys.

Ian

 

[Downey]

Do not 3 point motor mount (engine/bellhousing/transfer-case), your hot riveted frame is way too flexible and will rip out some of that motor mounting when you get into off camber off road terrain.

 

[JohnnyC]

@Downey is the one that knows

early 70's downey one:

 

[peesalot]

Downey is correct, mounting all three points tight will cause failure somewhere, I learned this and luckily only lost 1 of the two bolt journals on the bell house on pass side. I now have the bellhouse mounts on soft bushings and they dont rest on them they sort of hover and it does let the frame twist without breaking more mount points so far.

 

[ijonesinsp]

Downey is correct, mounting all three points tight will cause failure somewhere, I learned this and luckily only lost 1 of the two bolt journals on the bell house on pass side. I now have the bellhouse mounts on soft bushings and they dont rest on them they sort of hover and it does let the frame twist without breaking more mount points so far.

Just as an insurance policy then? If they're not tight, I don't understand why you would still use them.

 

[peesalot]

Right, too lazy to remove them, might be sorry and crack bell hse someday but I've put it to some good stress and I'm afraid to look now.

 

[Downey]

Correct, the cases of damaged motor mounts I've heard of were at the center (bellhousing) motor mounts.