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Thread: 5 Speed gearbox flaw repair

  1. #1
    Senior Member DMC-81's Avatar
    Join Date:  Apr 2014

    Location:  Florida

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    5 Speed gearbox flaw repair

    Hi there,

    I recently learned about one of the flaws in our 5-speed manual gearbox when the secondary shaft nut bored through the rear cover and dumped the gear oil out on the ground.
    image.jpg

    After taking my first ride of shame back home, I was able to repair it without removing the gearbox, and I'll post my adventure in this thread. But after the repair, I am guessing that the second gear rollpin had been bent or sheared in the event, as I recall it went into second hard when the nut backed off. After the repair, second gear engages normally, but now it sometimes pops out and I have a slight gear grinding noise when I'm not in second gear. I parked the car right away after diagnosing, but now I'll have to take the gearbox out to repair it.

    Looking on the bright side, I'll be able to address other things like the rear main seal, the pilot bearing, check/replace the clutch, replace the axle boots and lip seals etc. Again, I'll post my work in this thread.

    I have yet to remove the gearbox, but I have some questions for the community in advance :

    1) Please share any special considerations/advice on removing the gearbox. I have and will follow the Workshop Manual, have watched the Wheeler Dealer episode, and I know to support the drive axles when removing them.

    2) Who carries/ stocks a reinforced second gear rollpin?

    3) Are there any other rollpins that I should replace with the reinforced version?

    4) Assuming I have damage to the gears for second gear, who has stock?

    5) What are your opinions on who carries a good quality rear main seal (with the ribs) pilot bearing, etc.

    Thanks a bunch.
    Dana

    1981 DeLorean DMC-12 (5 Speed, Gas Flap, Black Interior, Windshield Antenna, Dark Gray)
    Restored as "mostly correct, but with flaws corrected". Pictures and comments of my restoration are in the albums section on my profile.
    1985 Chevrolet Corvette, Z51, 4+3 manual
    2006 Dodge Magnum R/T (D/D)
    2010 Camaro SS (Transformers Edition)

  2. #2
    EFI'd dn010's Avatar
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    Location:  Florida: Pinellas County

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    My VIN:    5003 Never placed Concourse

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    5 Speed gearbox flaw repair

    Looks like the nut broke free from the shaft on you. I have removed and rebuilt the transmission on my car many times, familiarize yourself with the manual for removal and you'll be fine and check things off as you go, it is easy to forget about the back up wiring. If you need a clutch, now is the time as well. I was able to do this on the floor with a notched piece of 4x4 on a floor jack. If you have a lift, even better...

    I don't have any advice past #1, I would love to work on mine at the same time, I have an annoying grind every time I shift into second I'd love to get rid of! I can tell you I got all my transmission gut parts from Rob Grady more than a decade ago, give him a shout.


    Sent from my iPhone using Tapatalk
    Last edited by dn010; 12-01-2016 at 09:32 PM.
    -----Dan B.

  3. #3
    Senior Member
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    8,569

    My VIN:    10757 1st place Concourse 1998

    The roll pin is not necessarily bent. When replacing the roll pin there is no "strengthened" roll pin but what we do now is after replacing the roll pin we put a smaller one inside the replaced roll pin. That makes it stronger. All of the vendors should have the regular pin and the smaller one. What bends the roll pin is forcing shifts, usually because of a problem in the clutch hydraulics. When removing the transaxle remove the oil BEFORE taking it out. Getting those little covers off of the bell housing is a pain in the a--. Support the motor after taking the transaxle out. Internal parts like gears for the transaxle are hard to get and expensive but you should not need any. All of the vendors can get quality parts but in some cases you may want good, used ones and not all vendors have that. Before removing the transaxle try Redline MT-90 and recheck your linkage adjustments.
    David Teitelbaum

  4. #4
    Senior Member
    Join Date:  Sep 2014

    Location:  West Sayville, N.Y.

    Posts:    1,350

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    Club(s):   (AZ-D) (DMA) (DOA) (DCUK)

    Quote Originally Posted by DMC-81 View Post
    Hi there,

    I recently learned about one of the flaws in our 5-speed manual gearbox when the secondary shaft nut bored through the rear cover and dumped the gear oil out on the ground.
    image.jpg

    After taking my first ride of shame back home, I was able to repair it without removing the gearbox, and I'll post my adventure in this thread. But after the repair, I am guessing that the second gear rollpin had been bent or sheared in the event, as I recall it went into second hard when the nut backed off. After the repair, second gear engages normally, but now it sometimes pops out and I have a slight gear grinding noise when I'm not in second gear. I parked the car right away after diagnosing, but now I'll have to take the gearbox out to repair it.

    Looking on the bright side, I'll be able to address other things like the rear main seal, the pilot bearing, check/replace the clutch, replace the axle boots and lip seals etc. Again, I'll post my work in this thread.

    I have yet to remove the gearbox, but I have some questions for the community in advance :

    1) Please share any special considerations/advice on removing the gearbox. I have and will follow the Workshop Manual, have watched the Wheeler Dealer episode, and I know to support the drive axles when removing them.

    2) Who carries/ stocks a reinforced second gear rollpin?

    3) Are there any other rollpins that I should replace with the reinforced version?

    4) Assuming I have damage to the gears for second gear, who has stock?

    5) What are your opinions on who carries a good quality rear main seal (with the ribs) pilot bearing, etc.

    Thanks a bunch.
    We have everything you need including the reinforced roll pin, 1st/2nd slide hubs and gears, shift forks, seal kits, Valeo clutch kits, sleeved hydraulics that last etc. I have rebuilt many UN1's and can get you out of trouble if you need help.
    Rob

  5. #5
    EFI'd dn010's Avatar
    Join Date:  Jul 2011

    Location:  Florida: Pinellas County

    Posts:    2,092

    My VIN:    5003 Never placed Concourse

    Club(s):   (DCF)

    5 Speed gearbox flaw repair

    If you take it apart, just remember to put the damn differential back In the correct way. I made that mistake once, cost me 8 hours of time!


    Sent from my iPhone using Tapatalk
    -----Dan B.

  6. #6
    Senior Member
    Join Date:  Sep 2014

    Location:  West Sayville, N.Y.

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    Quote Originally Posted by dn010 View Post
    If you take it apart, just remember to put the damn differential back In the correct way. I made that mistake once, cost me 8 hours of time!


    Sent from my iPhone using Tapatalk
    Sage advise. Strong hint....DO NOT FOLLOW DMC Workshop Manual F:06:02 Figure 14 which clearly illustrates the ring gear fitted to the wrong case half. What where they thinking?
    Rob

  7. #7
    LS1 DMC Nicholas R's Avatar
    Join Date:  Jun 2011

    Location:  Orlando, Florida

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    Club(s):   (DCF) (DCO) (DCUK)

    If you get the transmission out and apart an need any help, let me know and I can stop by sometime to help you out. I've taken apart quite a few and have some spare parts as well. Its pretty straightforward though so I'd be surprised if you had any issues.

    The transmission is pretty stout internally; I think it's pretty unlikely that you damaged any of the gears. Luckily, it will be obvious once you have it open.

    What happened to your damaged 5th gear cover? Did you weld repair it or did you replace it?

  8. #8
    Senior Member
    Join Date:  May 2011

    Location:  Northern NJ

    Posts:    8,569

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    Quote Originally Posted by PJ Grady Inc. View Post
    Sage advise. Strong hint....DO NOT FOLLOW DMC Workshop Manual F:06:02 Figure 14 which clearly illustrates the ring gear fitted to the wrong case half. What where they thinking?
    Rob
    DMC probably just copied that illustration right out of the Renault manual not realizing the orientation was wrong. It is obvious DMC did not put a lot of effort into creating technical documentation. If you think the DMC stuff is bad you should see other small manufacturers. Everything is a 2 step process, step 1, remove. Step 2 replace. All of the details are left to the reader's imagination.
    David Teitelbaum

  9. #9
    Senior Member
    Join Date:  Sep 2014

    Location:  West Sayville, N.Y.

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    I've read that they had their own illustrator for the manual. Someone should have brought him up to speed. What would Barrie Wills say!
    Rob

  10. #10
    Senior Member DMC5180's Avatar
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    Location:  Reedsburg, WI

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    Dana,

    Will you use a lift or just jack stands? I have photos of the last time I installed my transmission using jack stands if your interested in that method.


    Sent from my iPhone using Tapatalk
    DENNIS

    VIN 5180, Frame 3652, STAGE II​, DM-eng Solid State Solutions (RPM Rly, Dm.Lt.Mod., Fan Fail Mod. , FAN Rly, HS.Rly) , HID headlights, SPAX user since 2009, Eibach springs, M Adj. Rear LCA's, DPNW poly-sway bar kit, DMCEU LCA Stabilizer link kit, DMCMW Illuminated door sills, Aussie Illuminated SS Shifter plate, REAL MOMO EVO Steering wheel, DELOREANA Extended View Side Mirrors w/ Heaters, DELOREANA LED Door Lights.

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