5-Rib Reverse Failure

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Jaffa
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5-Rib Reverse Failure

Post by Jaffa » Mon Jun 29, 2020 3:42 am

All,
My trans has been making whines a bit and makes a slight grunchy whirring noise in reverse, especially on overun when depressing the clutch.
Well, when reversing up our moderate slope driveway last weekend it popped out or reverse. I tried again same thing happened, it gets going then pops out. I thought it maybe just the shifter so tried again and held the gear lever to stop it popping out. Bad mistake I think as it popped out twice on the run up the drive. So I gave up and went down, turned round and drove up forwards. It reversed on the flat although a bit more noisier than before.
This got me to thinking that maybe the reverse gear had stripped a tooth, especially as the third time it popped out twice but was still moving like as the gear turned it skipped a missing tooth.
I haven't removed it yet but drained the fluid today and ran a magnet inside over the bottom. No big chunks but a fair bit of small stuff. Looked into the fill hole on the side and saw this gear. Question is is this the reverse gear I'm seeing, and If I only go forward is it OK to drive to the mechanics to have the trans overhauled?.

Thanks for any advice.
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Craig

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asiab3
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Re: 5-Rib Reverse Failure

Post by asiab3 » Wed Jul 01, 2020 8:40 am

Yes that is one of the reverse gears. Reverse is the only gear set in your transaxle with straight/flat teeth, hence the normal gear whine when backing up. Fortunately, it’s also the only gear set that isn’t in constant mesh, so you should be able to drive it to the shop, but I would push instead of using reverse, lest any addition damage occur.

Good luck!
Robbie
1969 bus, "Buddy."
145k miles with me.
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Jaffa
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Re: 5-Rib Reverse Failure

Post by Jaffa » Wed Jul 01, 2020 11:58 am

Thanks Robbie. Off I go.

Cheers.
Craig

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Amskeptic
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Re: 5-Rib Reverse Failure

Post by Amskeptic » Sun Jul 05, 2020 10:37 am

Jaffa wrote:
Wed Jul 01, 2020 11:58 am
Thanks Robbie. Off I go.

Cheers.

Note that the 5 rib transaxles have known weak points, one of which is the devilishly difficult reverse gear adjustment. Too far back and you have stationary parts contacting rotating parts. Not enough, and you have lousy mesh that is prone to jumping out of gear. The Bentley manual talks about preloading the parts as you set the reverse fork, who knows if people follow it. Also, loose bushings/bores in the transaxle can allow imperceptible movement which gets rid of perpendicularity in the gear teeth over time ... then they become little wedges or ramps that throw it out of gear during loading or unloading.
Colin
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 118,840 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 89,009 miles

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Jaffa
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Re: 5-Rib Reverse Failure

Post by Jaffa » Sun Jul 05, 2020 6:15 pm

Well this tranny has slowly been getting noisier in reverse over the years with a definite nose like gears rubbing against each other. A bit whiny now and again and needs the left side seal replaced anyway as this is leaking. But It's being booked in for a rebuild in the next couple of weeks.
Craig

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