Rear Trans mount stripped bolt holes

89 RT4WD, 6-Spd Manual trans
The day I bought my car, I was doing my usual routine of looking over everything before i bought it. I had the engine running and the hood up, and gave it some throttle to listen for funny sounds. Sounded great, but i noticed the engine rocked quite a bit. I realized i could grab the intake manifold and rock the engine a bit, forwards and back. closer inspection revealed that the rear mount on the transmission seemed to be loose or worn out.

So a few days later, I have the car at home, and I start checkin it out. The bolts that hold the mount to the trans casing seemed to be loose. Unfortunately, when I tried to tighten them, they just kept spinning. I haven't pulled them out yet, but from my experience, when threads are stripped, it's usually the internal threads, not the bolt itself. I know that another RT trans wil be very hard to find, so I need to work with what I have.

I need some advice on thread repair.

I will probably first try to clean up the threads with a tap and use a clean set of the original size bolts. But I know this probably won't work.

I could try to re-tap the holes a bit bigger , and find oversized bolts... maybe. That seems like a lot of searching, and trial and error.

I have heard of thread repair kits, such of Helicoil, but have never used them, and don't know much about them. I researched a little bit, enough to know what a Helicoil is and how it works.

Have any of you used Helicoils in the past? Do you have any sort of feedback? Would this solution be sturdy enough to hold up to the rear trans mount, or is there a better alternative?
Thanks!

Comments

  • RTiAWDRTiAWD Band Wagon
    Ive use helicoils to repair valve cover bolt holes that were stripped in Detroit diesels and they seen to do just fine.
  • bam-bambam-bam Council Member
    Helicoils or other thread repair sleeves will work well there. Make sure to get deep ones (long threads). I have had to do this to one of my d-series boxes.
  • Thanks a bunch. I'm gonna look into this as a solution, now that I know it seems to be reliable.
  • JakerJaker familEE
    I used Helicoils to repair one of those exact holes on my transmission. I didn't get the long inserts, but was able to stack 2 of them to get the full thread repair, and then just trimmed the top one to get it flush. So far, so good.
  • danzdanz Wagonist
    helicoil, or if you are lucky, you can use bell housing bolts which are about 1cm longer, which MIGHT just bite into some threads a little deeper in the hole.

    ive had to do that a time or two... rookies strip those out like theres no tomorrow...
  • I'm starting to think the guy I got this car from maybe didn't know quite what he was doing. I have found several stripped bolts, broken bolts, loose bolts, and when he replaced the head gasket he set the timing belt wrong.
  • turbo_tegturbo_teg Council Member
    ya those 3 bolts are in a bad spot they just sit there and collect water. i cringe everytime i remove them from an ef and i try to anti-seize them when i put them back in if i remember. helicoil for sure.
  • Another question. If you use a Helicoil and you have to remove the bolts in the future, will the holes still be in a good usable condition, or will you need to use a new Helicoil to repair again? Basically, is this a one-time fix or a permanent fix?
  • danzdanz Wagonist
    i helicoiled one of the M8 bolts that holds the distributor on... ive taken that bolt out MANY times and its still a great thread.

    a helicoil is basically a coiled piece of alloy. it should be just as strong as the original thread.
  • If its I high load bolt I use a Time Sert, the Bolt hole is a 12mmX1.25 for reference


    Here's more info on Time Surts..

    http://www.timesert.com/html/mtrcsert.html
  • danzdanz Wagonist
    VIPwryann wrote:
    If its I high load bolt I use a Time Sert, the Bolt hole is a 12mmX1.25 for reference


    Here's more info on Time Surts..

    http://www.timesert.com/html/mtrcsert.html


    no doubt the time cert is a better option than a helicoil. but you pay for that.
  • JakerJaker familEE
    Helicoils are designed to be a permanent fix. Cannondale uses them for the bolt hole that holds the front wheel on my mountain bike fork. I have removed the front wheel at least a couple dozen times.

    However, as has already been mentioned, Timesert is a refined improved version of the Helicoil. And as someone has also mentioned, they are more expensive.
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