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Technical Chevy Styleline Transmission mounting height in relation to frame

Discussion in 'The Hokey Ass Message Board' started by Devin, Jul 29, 2016.

  1. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    I'm in the process of dialing in my engine and transmission mounts and in order to get the proper tail shaft angle I need to raise the transmission tail shaft so that its center is 1.5" above the top of the frame rail. Even at this height the angle is 4* and dropping below I'm at 8*+. This seems high to me. Can I expect to have interference with the floor at this height. Any other 49-54 Chevy owners encounter this? For the record the engine is a GMC 270 with a Saginaw 4 speed. Thanks. ImageUploadedByH.A.M.B.1469770499.165798.jpg
     
  2. aaggie
    Joined: Nov 21, 2009
    Posts: 2,531

    aaggie
    ALLIANCE MEMBER

    You will need to do something to lower the tailshaft, probably make a new cross member or cut out the center and make a new center section. As it sits it looks like it would hit the back of the floor tunnel and the shifter will probably be under the front of the seat. If you plan on using the factory pedals you will need to have them in place before deciding where to cut the cross member.
     
  3. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Thank you. I think I need to build new motor mounts on the frame to drop the engine down in front for a less severe angle. I will most likely be using a firewall pedal set up for exhaust clearance reasons.
     
  4. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    56sedandelivery
    Member Emeritus

    Member drew1988 just went through this with his 50 4 door sedan to V-8/auto swap. He may be able to answer your questions. Send him a PM. What complicates things with the 49-54 transmission cross-member, is that it is RAISED in the center; most cross-members are DROPPED in the center. I am Butch/56sedandelivery.
     

  5. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Hey Butch, thanks for the tip. I will reach out to Drew. What's weird is that my crank centerline and engine position are in sync with measurements provided to me by Flux Capacitor. In order to get an appropriate driveline angle I have to significantly raise the tranmission tail shaft. I'll figure this out but it's weird.
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 50,199

    squirrel
    Member

    I'm kind of confused...what angle are you trying to get the crank centerline at? 4 degrees nose high, relative to the frame? the pic looks like you need to drop the back quite a bit, to me.
     
  7. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,232

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    First place I would start is getting my chassis set on stands at the desired ride angle. Level, nose up or nose down......whatever you have in mind for the finished product. Then set the engine/trans to the desired centerline angle, in relation to the ground, and build mounts accordingly. And, as has been already stated, the stock Chevy crossmember is not friendly to power train swaps. It may have to go, or at the very least, be modified.

    Ray
     
  8. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Sorry for the lack of clarity guys. The angle is being set at ride height and measurements are being taken in relation to the level ground. I am ditching the stock crossmember. I'll do my best to take some better photos tomorrow. Thanks all for the insight.
     
  9. 49ratfink
    Joined: Feb 8, 2004
    Posts: 18,125

    49ratfink
    Member
    from California

    I'd like to help, but I can only look at your avatar picture so much before I need to turn away and look at another thread.
     
    bobss396 likes this.
  10. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Hey man it's how I am on the inside that counts!
     
    49ratfink, spooler41 and Hnstray like this.
  11. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,558

    Johnny Gee
    Member
    from Downey, Ca

    Not understanding why you need your output shaft 1 1/2" above the frame ? Explain please. Is your 270 mounted exactly as it should be ? If so your tail needs to come down until it's 3 to 4 degrees below level and not above as your photo makes it seem to be. If you can more pics from further away with the floor in it would help.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 50,199

    squirrel
    Member

    I don't see any need to set the engine angle relative to level ground....I set it relative to the frame. The design of the car was such that the engine would clear the frame crossmember, and the floor pan, with the nose of the engine up a few degrees (3-4 usually) relative to the frame.

    There are other ways to do it...but I like to keep things "as designed", unless there's a good reason to change it. The guys who designed these cars did know what they were doing, for the most part.
     
  13. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,232

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Your could set engine angle either way...In reference to the frame or reference to the ground. In most OEM installations, that is one and the same as the majority of production vehicles are designed to set about level at normal ride height.

    However, the engine/trans can be at most any angle as long as things affected by that angle are taken into account, i.e., driveline, carburetors, etc. I just think that if I was building a chassis with a 'rake' I'd set the engine/trans angle in relation to level ground, at least in initial mock up.

    The pinion height doesn't vary with chassis position (raked or level), though it would with rear tire diameter. As long as pinion angle is correct for drivetrain position, you can choose whatever suits you best.

    Ray
     
  14. flux capacitor
    Joined: Sep 18, 2014
    Posts: 676

    flux capacitor
    Member

    Devin, At final ride heigth, square with the world, I stabbed the 235 n Saginaw into the emptiness & positioned the engine to its original exact stock position "based on what seemed like 200 chassis measurements" that I'd took before oem removal. Now it's back 1/4 from stock. Luckily I had the body back in place at this time. I first built the transmission crossmember & lastly used the engine "side mounts" which unfortunately the Jimmy lacks" & altered the width of the new side mounts allowing me to adjust engines tilt till it hit the 4 degree mark, all based on the original gm position. I know those oem crossmembers shape well & it was best for my app to see it go. The stock member is just bassackwards of what it needed to be. I wonder if a measurement or two from the front frame horn to the end of the tail shaft & then a heigth from bottom of frame to the tail shafts center would help you determine floor board clearance? I percieve the gmc's centerline as compared to the chevy's a good way to compare resting heigth. I know you said it's slightly larger in many demensions than a 235. Even though that beast of a 6 is bulkier , based on centerline comparisons one could see if it's clear the floor's tranny tunnel? I think so. Ive soo little room to spare above the tranny. Let me know if you need any more measurements or pics. Flux. image.jpeg
     
    Last edited: Jul 30, 2016
  15. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    The only reason why the output shaft is 1.5" above the rails is because that is where it is angled down 4 degrees. If I drop it lower the angle is significantly greater. My engine is mounted fairly low as it is. I really do want the shaft to be below the rails. I'm going to build new frame mounts for the engine to see if I can drop it another inch or so.
     
  16. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    This makes sense. I will see what the engine ange is in relation to the frame.
     
  17. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Hello Flux, my crank centerline height in the front is right on with the measurements you sent me. Also the valve cover above frame rail is about the same. If you could provide a measurement from the frame bottom to throu tout shaft centerline I would really appreciate it. Thanks!
     
  18. Post a picture of your front mounts, definitely looks like the front of the engine has to drop. I know you had another thread going on the build.
     
  19. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Alright guys. Here's som pics I just took. I took my measurements Based off the angle of the crossmember and the flattest part of the front frame my engine is angled back another 3.5 degrees which is 7 degrees against level ground. The tailshaft is still around a little over an ice oboe the top of the frame rails. My biggest concern is being able to phase the tailshaft and pinion angles. Right now the pinion is tacked on in at 0.5 up in relation to the ground. Is the trans/ pinion angles phased based on actual angles to the ground or the frame angle? I know this has been gone over a million times but I'm a little confused now. Thanks for all the help so far. ImageUploadedByH.A.M.B.1469914379.568425.jpg ImageUploadedByH.A.M.B.1469914390.538324.jpg ImageUploadedByH.A.M.B.1469914411.866400.jpg
     
  20. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Going to drop the engine further this week. Will post results.
     
  21. squirrel
    Joined: Sep 23, 2004
    Posts: 50,199

    squirrel
    Member

    Like I said before, I ignore the ground when setting up the engine and rearend angles.

    I also like to have the floor and firewall in place, etc so I know that everything is going to clear. Making engine/trans mounts without ALL the parts in position, is asking for redo work.
     
    49ratfink likes this.
  22. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,232

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I think I see what at least part of your problem may be.......the oil pan is deep sump the entire length of it. Most pans have a deep area and a shallow area, usually depending on where the oil pump is located. The GMC, being designed as a hard working truck engine, and benefiting from a generous oil supply, has a full length sump. That could be altered at the front, thereby allowing you to lower the engine/trans several inches. With that done, I think you would have the alignment you are looking for.

    Ray
     
    Last edited: Jul 30, 2016
    6inarow and squirrel like this.
  23. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    We all use different ways to easily understand things.

    My clearest way (for me) to see if I have something way wrong, because I was under the car measuring off the tail and pinion yoke...and if I get befuddled with a poor view..

    I get along the car or chassis and if the front of the motor is up X degrees, the pinion needs to also be up the same X degrees. Then a 2 joint driveshaft will have matching joint angles.

    When I'm under the car with the machinists level I have, if I go off the trans, I need to reverse that reading for the pinion with this type of tool. Not good if you are tired and can't really see the actual tilts of both
     
  24. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    I've got some work to do! Everyone has made some very strong points. My firewall and floor are rusted to hell so I can work around this somewhat when I rebuild. Based on measurements off a stock car I should be clear of the firewall but will have to move the radiator forward slightly. I have 2" of clearance between the oil pan and crossmember so the engine will be dropped further and I may even section the oil pan but was hoping to avoid this. I will reference all angles against the frame and provide detailed info what I do to solve the problem in hopes that this can help someone else. I appreciate the advice!
     
  25. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,558

    Johnny Gee
    Member
    from Downey, Ca

    Here's to money shot Jim I was referring to. With all aspect's in vision now, engine & trans, frame and ground, the illusion that the engine and trans is tail up (very first picture) is absent now. The illusion came from the frames rails because they narrow towards the front. Now I can diffidently say OP is doing just fine. :) [​IMG]
     
    Last edited: Jul 31, 2016
  26. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Thanks Johnny G! I started making new frame mounts which will drop the engine in front about 1.25". I'll see if that helps. ImageUploadedByH.A.M.B.1469993817.593291.jpg ImageUploadedByH.A.M.B.1469993829.046382.jpg
     
  27. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    They will be getting gussets, I ran out of time.
     
  28. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,558

    Johnny Gee
    Member
    from Downey, Ca

    The only other thing that I can see that other haven't pointed out or you haven't mentioned is your clutch linkage. If your going with the o.e. mechanical watch for the link bar not being to much out of line. Because when it's badly out of line (horizontally), it'll place odd forces on the fork which will then transfer over to how easily the throw out bearing will slide on the bearing retainer. [​IMG]
     
  29. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,091

    gimpyshotrods
    ALLIANCE MEMBER

    I would drop that to 1", which will probably end up being 1/2" after the mounts settle.

    I have not yet done a MII front with an L6 in, a '47-'54 car. I have done it in a '47-'54 pickup, and that required that the front engine mount be raised to clear the crossmember.

    To keep the transmission under the stock floor, you might have to notch the crossmember.

    My best recollection from modifying the stock transmission crossmember to accept a TH350 or 700R4 put the tailshaft roughly dead half-way up the height of the frame rail. In other words, way lower than where you have it.

    I am a wiz an measuring stuff, especially in the abstract. If you have the body nearby, I can walk you through figuring how to get it all to fit under the stock floor.

    Or, better still, I will be at Sears Point this afternoon for drag racing. If you want some help, send me a PM. Either way, I am not possibly more than 45-minutes away from you.
     
  30. 6inarow
    Joined: Jan 24, 2007
    Posts: 2,330

    6inarow
    Member

    228/248 oil pan might help too
     
    Hnstray likes this.

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