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Solid Transmisstion Mount??

5K views 21 replies 10 participants last post by  ITSA 91 
#1 · (Edited)
I'm working on the Mustang today. I have the motor where it needs to be with the motor plate attached. I didn't like how high up the transmission mount pushed the transmission into the transmission tunnel. I've made a solid transmission mount that will attach the transmission to the transmission cross member. It seems like it will work fine but I'm a bit worried about having no flex what so ever without a rubber or polyeurethane bushing. Does anybody see or know of a reason why I should not use a solid transmission mount bushing?
 
#2 ·
Don't ever use a solid tranny mount bushing almost a garauntee to crack the trans case.

Chris their should be a short one and a tall one I believe the difference is stick or automatic.

But the trans will be a super tight fit on these cars you will need 90* fitting coming out of the tranny for the lines and always install the lines before final engine and trans installation.
 
#4 ·
10-4. I'll use it today just for the mock up. I'll look into what Summit & Jegs have as an alternative. The stock one that I bought from Autozone was just too tall and the top of the trans was just too close to the trans tunnel. I'll see if I can get a shorter one. I'm glad I posted this question. I had a feeling that was the answer I was going to get.
 
#7 ·
You have to see what your driveshaft angle is, and if the intake manifold carb flange is level and let those determine which mount you use. Placement in the tunnel is a non issue compared to those. But do not use a solid trans mount with a motor plate.
 
#8 · (Edited)
Thanks Clay.. That helps. I can see why you would need to fab a trans tunnel. That great big C6 in there is tight. The whole thing came about when I could not get the trans cross member bolted in when the trans was about an 1/8 of an inch away from the top of the trans tunnel. So I made a transmission mount bushing that lowered the trans away from the trans tunnel about a 1/2 inch. It was obviously touching up top somewhere and it would not allow me to get the bolts started for the trans cross member. After I put the solid mount in that I made I got the transmission cross member bolted in with no more problems. I checked all around and seemed to have clearance everywhere. I however knew that the solid mount was a bad idea. That is why I asked before I tried to run it down the track. I'll have to see if I can get a shorter transmission bushing. I had a stock one ($15 bucks from Autozone) that I was trying to use to mock the engine up so I could get the motor plate mounts weleded in. I did get the motor plate mounts in and welded and everything bolts up real nice now. I'll just have to get a new transmission bushing.

As for the driveshaft angle and levelness of the carb flange.... I have no idea what the drive shaft angle will be. I still have to measure for the driveshaft and order it (I'm going to get a Strange chromemoly unit). I can do that now that I have the motor & trans in where they will go. The carb flange definitely tilts down toward the back. The motor plate that I have sits the motor lower in the engine compartment and I have the rear of the transmission just about as high in the tunnel as I can get it without it touching and rubbing stuff. Im not sure how I could get the carb flange completely level. That almost looks like an impossible mission to me. There is always going to be some tilt to it. With the motor lower & the rear of the trans as high as it will go I'm thinking that is going to have to do. Your thoughts on this??
 
#10 · (Edited)
#11 ·
I have a stock style rear suspension car (however there are no more stock parts other than the rear spings but those are brand new). The trans cross member bushings are rubber. I bought the FoMoCo adjustable transmission cross member that you have to weld the bushing mounts in place when you get them where you want them.

I'll read the article Clay thanks.

I know you want the carb as close to level as possible but I just don't see how that can happen in this car. Lots of guys have to have the same issue with this as me and I'm betting they didn't do as through a job as you have by replacing the whole trans tunnel. And when I think about it with all the off road Jeep people that tilt their motors to all angles and even the drag race wheel standers they sure don't keep their carb level when they are doing that stuff and they don't seem to cut out because of fuel starvation. So I'm a little fuzzy on why the carb has to be perfectly level. The only real reason I can think of to keep it level all the time is the oil pickup in the pan. You don't want to get a big gulp of air in the oil pan pick up or have the oil run away from where the pick up is. But even with that being the case I have a oil pan with a rear sump so all of the oil will be running towards where the pick up is. I'm sure this thing is going to pull the front wheels but I don't know how high. But again that is controllable. I'll start off slow and work up... If anybody has any thoughts on this Foxbody carb level thing let me know please... I'm all for learning. I'm just not sure why it has to be perfectly level.
 
#12 ·
I have always set my engines at -4*, every stock engine mounting I have measured was also -4*. I have also found that quite a few intakes have a +4* built into them which sets the carb level. I read that this helps oil drainback and have always done it.
 
#16 ·
There is no magical "one size fits all" engine height/engine angle/driveshaft angle/slip yoke angle/pinion angle profile that will work with every car combo. "Drag race only" cars generally can use a different driveline angle profile than a car that only sees street/highway use.

"Street/highway" driven cars. For long U-joint service life under the never ending/constant/repeated partial loading-unloading "hammering" a street driven car's driveline sees for 1000's & 1000's of miles, both front & rear U-joints need a few things to help them live........

1 - Both U-joints need to be operating in "phase" with each other (being at/as close to "equal but opposing operating angles" as possible).

2 - Both U-joint's operating angles them selves need to be at least enough to (A) insure enough cap/needle-bearing rotation & self lubrication during use. But (B) not be at too much of an excessive operating angle where the U-joints are operating at/close to being in a bind at a given driveshaft RPM range.

This generally means that this "repeating partial loading" profile has (A) the pinion's centerline pointing at the same/similar angle as the crankshaft centerline (in relation to the ground), while at the same time the pinion height off the ground vs the crank height off the ground has enough difference that it gives you equal but opposing U-joint operating angles (or interference angles if you want) at both U-joints. The actual U-joint operating angles needed really depend on the rear suspension type used. A rear suspension that has limited pinion/housing upward rotation potential (like say a 4-link with stiff bushings) could get away with somewhere around -2.0* operating angle between the driveshaft & the pinion, and around +2.0* operating angle between the driveshaft & the slip yoke. Having "equal but opposing" U-joint operating angles on a car with a lot of pinion rotation potential (like say a leafspring car without a traction device) can sometimes be a can of worms to deal with. On one hand the leafspring's increased possible pinion rotation can sometimes call for more U-joint operating angle (at the pinion). But putting the same increased operating angle at the slip yoke U-joint (to stay in phase) can sometimes cause it's own problems.




"Drag race only" purpose built cars driveline profile (ladder bar & 4-link). Generally speaking on a drag only car you are less worried about a U-joint's "long service life" over 1000's of miles & more worried about reducing U-joint friction under heavy launch loading. So in this application they are looked at more as a periodic replacement maintenance item. As you build the car (while sitting at the proposed ride height) you in effect mount the engine/trans in the chassis so it's crank centerline points directly at the pinion's centerline & the pinion's centerline points directly at the crank centerline. This in effect gives you front & rear initial mock-up U-joint operating/interference angles of 0.0 degrees at both U-joints. Then after the car is finished & on the ground you adjust in a small amount of downward operating angle back at the pinion U-joint. So in the end (with say a 4-link) you might end up with only around -1.0* (one degree) operating angle back at the pinion, and only around +0.5* (a half a degree) operating angle at the slip yoke U-joint. The theory is that under heavy launch loading the pinion will rotate upward a small given amount (under load) making both U-joints operate at as close to 0.0* as possible (again under load) for the least possible amount of frictional losses through the driveline.
 
#18 ·
I appreciate the post. It helps. I'm going to try to get the angles as close as possible. The rear upper & lower control arms are adjustable so I'll be able to chase it around a bit. I'm also going with solid u-joints. I'm not sure how to mount the alternator with the motor plate so at least for now it will be a track only car.
 
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