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Dogbone Preloading - or - Hey hand me that calibrated Newton thingy by Rsvl-Rider
Started on: 07-16-2014 03:08 AM
Replies: 4 (145 views)
Last post by: Rsvl-Rider on 07-16-2014 12:39 PM
Rsvl-Rider
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Report this Post07-16-2014 03:08 AM Click Here to See the Profile for Rsvl-RiderSend a Private Message to Rsvl-RiderEdit/Delete MessageReply w/QuoteDirect Link to This Post

I've been trying for some time to solve my transmission "clunk when shifting into drive" problem. I posted the question here a couple of times and got lots of helpful suggestions and opinions. Actually I learned quite a bit about my car as a result. Other posters with the same problem just live with it in frustration and others reported successful resolutions using a variety of methods that had worked for them. Install the poly dogbone, install the solid dogbone, remove the poly dogbone and go back to the original bushing, elongated mounting bolt holes, bad CV joints, worn out engine mounts, tranny mounts, wheel bearings and brake calipers to name a few.

Several responders advocated "preloading" the engine position and suggested various methods for accomplishing this before tightening the dogbone attaching bolts. I found numerous references to this in my search of the archives. None of the research that I could find contained a reference for this practice or any authoritative source for "how much" or "how far" but the process generally falls into one of two possible methods. One is to put a come-along strap over the engine and ratchet it rearward until the dogbone bolts will slide in. The other seems to involve manipulating the throttle and the gear shift in such a way as to induce a torque-twist in the desired direction and then quickly tightening down the bolts. Seemed kinda iffy and arbitrary to me. It felt anecdotal and unsupported. But it kept coming up. So I scoured my Haynes manual but could find no reference other than simply..."install the strut mounting bolts and tighten them to the specified torque".

But then came my Eureka moment! In the GM Service Manual for the 88 Pontiac Fiero. I found it! There it was in black and white. On page 6A2-8, Figure 5, in the Note at the bottom of the page.

It reads..."Note: to position strut in support, push engine rearward with a horizontal load of 200-250 Newtons. Load is applied on a line directly through center of support slots. Tighten bolt with load applied".

Finally, the authoritative basis for the preload suggestions. The answer to my problems. The end to my frustrations. So hand me that calibrated Newton thingy out of my tool box and let me get on with my life.....


------------------------

No, I haven't tried it yet. I think I might need one of those giant chalkboards like you see in universities, and someone smarter than me to stand in front of it and scribble equations all over it.

Actually I'll probably snug it up with a strap, and then put one more click on the ratchet than it probably needs ('cause it's in my nature to do so), tighten that sucker down, and then finally just "Let It Be".

For those of you interested in Newton units check this link...

http://en.wikipedia.org/wiki/Newton_%28unit%29

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tesmith66
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Report this Post07-16-2014 07:06 AM Click Here to See the Profile for tesmith66Send a Private Message to tesmith66Edit/Delete MessageReply w/QuoteDirect Link to This Post
I never have understood why GM just didn't bolt these drive trains in instead of letting them flop all over the place. When I swapped in the DOHC, I put it on 4 real motor mounts. No dogbones, no struts, no worries.

And no need for a calibrated Newton thingy.
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Kevin87FieroGT
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Report this Post07-16-2014 09:13 AM Click Here to See the Profile for Kevin87FieroGTSend a Private Message to Kevin87FieroGTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Had to check it out. 200 newtons = 44.96 pounds. Really not that many pounds.

All good info. Thanks for spotting that in the service manual!
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Blacktree
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Report this Post07-16-2014 12:06 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yeah, you can convert to pounds and use your bathroom scale, in a pinch. BTW, 200-250 Newtons converts to approximately 45-55 pounds.

I didn't read the other thread. But have you checked the lower engine mount? If that mount is bad, then messing with your dogbone will be a waste of time.

And last but not least, why did you start another thread on the same subject? Your other thread is still on the first page.

[This message has been edited by Blacktree (edited 07-16-2014).]

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Rsvl-Rider
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Report this Post07-16-2014 12:39 PM Click Here to See the Profile for Rsvl-RiderSend a Private Message to Rsvl-RiderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Blacktree:

Yeah, you can convert to pounds and use your bathroom scale, in a pinch. BTW, 200-250 Newtons converts to approximately 45-55 pounds.

I didn't read the other thread. But have you checked the lower engine mount? If that mount is bad, then messing with your dogbone will be a waste of time.

And last but not least, why did you start another thread on the same subject? Your other thread is still on the first page.



I can't begin to imagine how I would use a bathroom scale to accomplish that procedure.

I had all the mounts checked by a transmission shop. They were all good.

I started a new thread because the other thread and title has been hashed and rehashed and so sometimes people don't "read the other thread". Since there was new and authoritative info to make available I thought a new thread with a dogbone preload specific, and easily searched, title would be a better way to do that. Apart from that... I thought I could have some fun with the title. OK?

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