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Discussion Starter #1
Think I might have messed up the transmission mount height in doing the engine/transmission swap -- from the original 305/TH350 to LT1/4L60E ('84 El Camino). It wore out the bushing in the transmission and left a matching wear groove in the front yoke. I replaced the yoke and bushing and rear seal a couple thousand miles ago and wondering why it wore like that. Should the front U-Joint be straight, and the rear have the rear axle angled down just slightly from straight? I have poly rear control arm bushings in boxed control arms if that makes a difference in the rear U-joint angle.

Thanks for the help.
 

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The angle of the transmission should be on the same plane as the pinion on the rear end, within 2 or 3 degrees......
One of those plastic protractors from a home building supply place works good for this. With the drive shaft off, check the angle of the flange on the rear end. You need the 90 degree angle to that, to compare with the angle of the transmission. The bottom of the starter on the engine is a good place to find the angle of the trans (and engine). Within 2 to 3 degrees difference is desired, between the transmission and the rear end pinion, which you measured on the pinion flange.

Making the trans tail shaft higher or lower with the mounting at the cross member is one way. If it's a radical angle, adjustable upper control arms on the rear end can be used to make the trans & rear on the same plane.
Hope this helps some.....
 

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i took an old trans yoke and had the u joint bosses milled flat just for checking trans angle. which tail housing do you have. i used the one without the mount and always had an angle issue,i couldnt get the trans low enough so i went to the b body tail housing that has the mount on it and a 200r4 crossmember and it got it low enough to get the angle where i needed it. you need a angle change from the trans to drive shaft and from driveshaft to pinion yoke to stop u joint wear and vibration. you should have between 2 and 4 degrees.both ends should have the same angle change. they make mount shims and adjustable upper arms to set it right
 

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Discussion Starter #4
Both ends should have the same angle change -- that's the info I needed to work the issue. I have a protractor that can read the angles, but needed to what they should be. Thanx
When I did the swap I was fighting clearance between the forward yoke and the floor/tunnel brace that goes under it, so I probably have the trans mount shimmed too high. Took me till now to think about how to measure the U-Joint angles.
 

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Think I might have messed up the transmission mount height in doing the engine/transmission swap -- from the original 305/TH350 to LT1/4L60E ('84 El Camino). It wore out the bushing in the transmission and left a matching wear groove in the front yoke. I replaced the yoke and bushing and rear seal a couple thousand miles ago and wondering why it wore like that. Should the front U-Joint be straight, and the rear have the rear axle angled down just slightly from straight? I have poly rear control arm bushings in boxed control arms if that makes a difference in the rear U-joint angle.

Thanks for the help.
One simple way to check, IF you haven't changed your rearend: remove the carb and put a level on the intake. It should read level. That would put about 3-4* down on the back of the tranny for the 3-4* up on the rearend. That makes them match.
 

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the drive shaft safty strap will need to be reshaped to clear that interferance is common in a unmodified strap with a 700/4l60/e trans. a lot of people just take it off .modify it or shim it down away from the yoke.you really want it there
 

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Discussion Starter #9
Yeah, I've been running without that strap since the swap. Guess I'll get some flat stock and make one to fit.
 

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The strap you guys are talking about........never heard of that. clue me in !!:smileyb:


Safety hoop. Keeps the prop shaft off the ground in case a U-joint or yoke fails. Even though Mythbusters busted the myth that a broken driveshaft can flip a car.

Also, I reserve the right to be 100% wrong, I'm not an axle specialist.
 

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So much for Mythbusters, I have been in one that flipped when the front of the driveshaft hit the pavement.
 

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I get infuriated with their methods. Then they have the nerve to call themselves "experts" in the disclaimer at the beginning of the show. :let_it_all_out:
 

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Yep so much for that myth. I served as an expert witness in a multi million dollar case involving a Ford f250 that dropped a front joint coming off a ramp on I-75 (just south of Tampa) and left the driver a paraplegic from the truck flipping many times. Long story short is the grease that comes in a new U-joint is only a preservative to keep it from rusting during its shelf life. Joint must be lubed during install.
 

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The story

I was helping my brothers friend do some work on his IH Scout. Kind of like this one only without the roll bar.


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On a test ride with him driving, his girl friend in the middle and me on the right side.(no seat belts in it) A lift kit had been added, not quite correctly. The rear housing turned in the spring clamps and pulled the drive shaft out of the transfer case. The shaft dug in and flipped the truck to the left towards on coming traffic. It ended up partially in the ditch, upside down on the other side of the road. Kind of like this.


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As it flipped it dropped me out on the pavement and cleared me. Traffic had room to stop. He and the gf were underneath it. She came crawling out but the windshield frame had folded back and had him pinned across his chest. As fuel is leaking out, I am asking the gathering crowd for a jack to get the pressure off him. The fire dept showed up quickly and used the "jaws" to jack it up enough to slide him out. No fire (thank you Lord) and no serious injury.
 

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Don't EVER believe a vehicle can't jack-knife when the front of the drive shaft drops down and makes contact with the roadway. That's why the safety device was/is installed - to hold the drive shaft up while the vehicle cruises to a stop - no drive shaft and no forward movement.:poke:
 

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as i said you really want it there.every sanctioning body requires them in competition cars and your h or x pipe doesnt count as one either
 
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