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Technical How would you solve this flexplate/starter interference problem?

Discussion in 'The Hokey Ass Message Board' started by Just Gary, May 1, 2021.

  1. When energized, the starter's pinion gear bangs into the side of the flexplate, with a ringing sound, instead of engaging it's ring gear teeth.

    Engine: '58 354 Chrysler truck Hemi. 8-bolt crank flange.
    Trans: 1992 Chevy 700R4.
    Adapter & flexplate: Black Mountain Hemi, since gone out of business.
    Starter: Standard Mopar 2-bolt starter. Checked good at local AutoZone this morning.

    Here's a 3/16" allen wrench between the ring gear teeth & starter shaft.

    As an experiment, I inserted a 0.075" thick flat washer on each starter mounting stud, between the adapter & starter housing. This moved the starter forward, *away* from the flexplate.

    When energized, the pinion just barely engage the ring gear (<25%) but did spin it. It didn't slide back & disengage when de-energized. Shouldn't it have?

    Finally, I removed the washers and left the nuts on the studs, loosely holding the starter in place. I bumped it over- the starter wobbled around, then the pinion fully engaged the ring gear and spun the motor. This tells me that there is *some* starter orientation that allows the gears to mesh correctly. BTW, it still didn't disengage when de-energized.

    At this point, what would you do?:confused:
    Anyone ever shimmed a Mopar starter (like a Chevy)?

    Am trying to post videos of the 3 scenarios above, but the MP4 format isn't being accepted.:rolleyes:
    Last edited: May 1, 2021
    Dino 64 likes this.
  2. Budget36
    Joined: Nov 29, 2014
    Posts: 6,984


    You need to pull, push the pinion gear out and look at the mesh, should be able to get an 1/8in Allen ( what I check Chevy starters with) between the pinion gear and ring gear. Start from there I’d think?
  3. Budget36
    Joined: Nov 29, 2014
    Posts: 6,984


    If not enough clearance, you might be looking at having an offset stud made to rotate it away. Should just need one. Would have to be threaded on both sides
    I’d think.
    Id guess the other option would be to have the adapter slotted the filled/sleeved to move the hole(s) over.
    Last edited: May 1, 2021
  4. 51504bat
    Joined: May 22, 2010
    Posts: 2,932


    You need to post the video to U Tube and then post the link here. I have no idea how to go about doing that but maybe you have a 13 year old relative that can handle it for you?
    vtx1800, VANDENPLAS and Just Gary like this.

  5. More pics:
    20210428_184729~3.jpg 20210428_184742~3.jpg
    Chavezk21 and Dino 64 like this.
  6. Correct number of teeth on the flex plate?
  7. oldiron 440
    Joined: Dec 12, 2018
    Posts: 2,299

    oldiron 440

    I would check the thrust on the crankshaft, see just how much it is moving back and forth. I don't have an old hemi but I've never had to shim a starter on my big blocks in 38 years.
    Just Gary likes this.
  8. triumph 1
    Joined: Feb 9, 2011
    Posts: 581

    triumph 1

    From your pictures it looks like you could probably elongate/slot one of the starter mounting bolt holes to get the proper pinion to ring gear clearance?

    Sent from my iPhone using H.A.M.B.
  9. Corn Fed
    Joined: May 16, 2002
    Posts: 3,001

    Corn Fed

    Does the pitch of the teeth on the custom flexplate have the same pitch as the Mopar flexplate the starter was made for?
  10. TRENDZ
    Joined: Oct 16, 2018
    Posts: 310


    Mopar starters have one oversized hole for some slight adjustment. You could go slightly bigger with both holes and make sure that the big hole that the nose cone goes through has enough clearance to utilize the added “slop”.
    Dino 64 and Just Gary like this.
  11. pirate
    Joined: Jun 29, 2006
    Posts: 664

    from Alabama

    If the number of teeth on flexplate is correct and pitch is correct you may have to put a spacer between end of crankshaft and flex plate. Summit/Jegs and others sell the spacers from about .030 up to about .090. Or you can use them in combination. That is if I understand the problem correctly.
    VANDENPLAS and Just Gary like this.
  12. I’m betting the flex plate is okay,,,,,I think the mounting studs for the starter are ever so slightly off location.
    It wouldn’t take much to cause it to bind .
    Elongate the top hole just a little and see what you have ?
    Should let the pinion swing away a little,,,,and clear the ring gear .

    Hemi Joel and Just Gary like this.
  13. Are you sure you have the right starter?Im not a Mopar guy,but I do know theres 2 different automatics in Mopar world.Could be you need the "other" one....or one from a manual trans.Just a thought.
    Just Gary likes this.
  14. Where have I seen this before ?
  15. Stop using Batt. power to engage the Bendix. Use a pair of offset needle nose pliers and manually do it. You want .020 back lash between the gears. Find out what the Tooth count is on the Flex plate the starter is made for in it's stock application. In other words male sure the 2 items can work together. If the 2 items can work together then decide how you want to move the starter away from the ring gear and once done make some kind of lock pin be it a small dowel pin or a simple bolt threaded into the adapter plat for a dead stop.
    Dino 64, Just Gary and squirrel like this.
  16. squirrel
    Joined: Sep 23, 2004
    Posts: 49,536



    The Mopar starter has that pilot around the end of the the nose cone, which fits into a hole in the transmission case. This is what aligns the starter on a Mopar, the bolt holes are oversize to allow the starter nose to fit into the pilot hole. Since the pilot hole is missing in this conversion, you have to find another way to locate the starter exactly where it needs to be.

    We can't see the gear mesh in any of your photos, either. How about if you do like he suggested, pull the starter drive out to engage the teeth, then take a picture from the perspective of this one, so we can see how the teeth mesh? Then we might be able to offer an opinion about whether it's too tight, or too loose.

    I like the idea of using a dowel to locate the starter, although it's not going to work when you have to replace the starter eventually.

    Last edited: May 2, 2021
    Dino 64, Hemi Joel and Just Gary like this.
  17. PROGRESS!:)

    I followed @triumph 1 , @TRENDZ , @Desoto291Hemi and @squirrel 's advice, grinding out one side of a starter mounting hole ~1/8" with a demmel.


    After. The duct tape was to keep dust out of the solenoid:

    Then I mounted the starter & bumped it over. The pinion teeth *fully meshed* with the ring gear & spun it, but still didn't retract.

    Also, the gap between the pinion & ring teeth was still too small to squeeze a paperclip between 'em.

    I had to quit for dinner but tomorrow will grind the hole a little bigger so the teeth mesh with a paperclip size gap between 'em.

    Thanks everyone for your ideas.
    Having to modify a stock part to work with a custom part is truly annoying, but I guess sometimes that's just what ya gotta do.:rolleyes:
  18. Aint it annoying how often parts don't work as designed? Looks like you have this problem on the run at least
  19. X-cpe
    Joined: Mar 9, 2018
    Posts: 1,218


    Most parts work as designed, we're just habitual un-designers.
  20. I had 3 different parts store starters for the 283 in my 39 (bell housing mount not block mount) that either would not bot up or did exaclty this. I eventually rebuilt an original GM starter from a 65 chevy pickup and it worked perfect. i would look at getting another starter from Mopar. some of this stuff that we get now is just absolute junk.
    Just Gary likes this.
  21. You're getting there. The root cause was your pinion gear on starter was not spaced out far enough. Your grinding helped, and now it engages, but is too tight for the disengagement. Can you offset the lower hole as well? I can;pt see how that mounts in your pics. Or grind a little more on the top hole. Goal is to move the pinion out way from the flexplate a bit more.
    wfo guy, Tickety Boo, Dino 64 and 2 others like this.
  22. X-cpe
    Joined: Mar 9, 2018
    Posts: 1,218


    Maybe when you get the hole egged out to where it works right you could make a bushing and epoxy to in the hole so the starter doesn't move.
    73RR, osage orange and Just Gary like this.

    After a little more grinding in both holes, l mounted the starter & bumped it over. The teeth are fully meshed & spin the flexplate but they still don't *disengage*.

    Shouldn't they??:confused:

    A paperclip slides easily between the teeth tips & roots:
    20210503_142201~2.jpg 20210503_142119~2.jpg
  24. Of course the solenoid retracts the pinion if the engine starts running.
    But if it *doesn't* start running (like in this case) is it normal for them to remain meshed?:confused::confused:

    I can easily disengage them by pushing/prying the pinion with a screwdriver.

    Or is the solenoid faulty? The AutoZone tester claimed that was included in their starter test.o_O
    Last edited: May 3, 2021
  25. I don’t think a paper clip is enough clearance,,,,,,it will fit at the bottom of the tooth basically .
    Try a little more,,,,,,then when it works,,,,,measure your clearance .
    Can you use a tool of some kind and make it retract,,,,,you are getting close I believe .

    Just Gary likes this.
  26. Find out what tooth count is correct for that Starter Bendix. You can have the same dia. ring gear with a different tooth count. The other option is to make sure you have some backlash between the gears when fully engaged. My guess is that the 2 items are not a matched set.
    Dino 64 and Just Gary like this.
  27. 10 tooth starter. 131 tooth flexplate, 13" diameter.
    Dino 64 likes this.
  28. 73RR
    Joined: Jan 29, 2007
    Posts: 6,602


    The Mopar ring gear would either be 130 or 146 tooth so your 131, although a bit odd, should work.
    I might suggest that you also try a Dakota starter. If nothing else, they are a bunch lighter/smaller.
  29. Something there just don't add up. After dinner I'll go open up my new kit and count up what mine has and get back to ya.
    Dino 64 likes this.
  30. blue 49
    Joined: Dec 24, 2006
    Posts: 1,426

    blue 49
    from Iowa

    I had a Chevy rebuilt starter that the pinion wouldn't return all the way on its own. Turned out the slug in the solenoid didn't have enough clearance and spring couldn't push it back.

    Just Gary likes this.

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