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How fragile is a Spridget gearbox?

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zedvictor1 Avatar
zedvictor1 Steve L
Albion, WA, USA   USA
The last two Sprites I have driven had unpleasant gearboxes: VERY noisy in first and crunches when changing gears (up or down) even when double-clutching. Could this have been a clutch and not a gearbox issue? I've read here that the gearbox is weak in the pre-1500 cars. How weak is it? How long should a rebuilt box last? I did drive a very nice restored Sprite as well, and that gearbox had no problems at all . . .

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scoutll Avatar
scoutll Bryan Durham
ND, USA   USA
1965 Chrysler 300 "Annie"
The ribcase gearbox is actually very robust when treated properly and kept full.
They tend to be a bit noisy, especially in first gear, which is straight cut. Most I have ever seen produce a certain amount of noise from the rear end too. More noticeable with the top on the car.
If you try to shift into first or reverse while moving it is going to grind... nonsync.
The best practice is to downshift without skipping gears, and always go to second before shifting into first. Don't try to shift into first until stopped, or at least below 5 mph. Once you get to know your car, you will learn what is normal sounds, and what may be abnormal.
If it grinds when trying to engage first or reverse from a stop, or between gears, your clutch may not be fully disengaging. Could be the slave cylinder, or another common problem is worn holes or clevis pins on the pedal pivot or slave cylinder pushrod.

7mg2 Avatar
7mg2 Andrew Hardie
Calgary, AB, Canada   CAN
1969 MG MGC GT "Mr "C"
1972 MG Midget MkIII
Great post Bryan.
I think it needs to be stressed, that these gearboxes will take quite a bit of abuse, but they are not immune to defects caused by misuse or poor/lack of good lubrication, and a common cause of problems is from the use of gear oils for lubrication instead of engine oil which is the recommended oil. Gear oils have a detrimental effect on synchronisers and other non ferrous materials in the gearbox. Perhaps this was the case with the cars you have previously owned. Also, the earlier "smooth case" gearboxes were not as robust, or as smooth as the "ribcase" which came into being with the later 10CC 1098 engine in 1964 and stayed with us until the 1500 cars of 1975.

Noisy first and reverse gears are not uncommon, especially now that these components are getting quite old. These gears are straight cut, and noisy in nature as a result. In many cases a complete rebuild using new components will quiet them considerably, but they will probably still be a bit noisier than when new.

Many racers around the world over the years have put as much as twice the original power output through these gearboxes without causing catastrophic failure, so in normal use, they are as Bryan said, "very robust".



Andy

NAMGBR# 20-7738
AMGCRA# 1678

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zedvictor1 Avatar
zedvictor1 Steve L
Albion, WA, USA   USA
I see. Perhaps I have forgotten how noisy they are, but with my advancing years and hearing loss you'd think the cars would be quieter!
It could all boil down to age (the car's) and poor maintenance. Today's drive was in a 62, so probably the smooth case box. I was just remembering a thread from a few days ago that stated the A-engine cars had a good engine and poor gearbox; whereas, the 1500's had a poor engine and good gearbox.
All the same, I must say that it was great to drive with the top down (off) on a sunny 32-degree day! Ahhhh. My hat didn't even blow off at a heart-pounding 40mph!

GLA72 Paul R
adelaide, adelaide, Australia   AUS
I crashed the gears for a couple of thousand miles before i learnt how to drive proper. It's all about catching the revs. Like in a truck. Only using the clutch for R, 1st double clutching to 2nd. Same with downshifts. Now I can keep my left foot on the brake so deep in the corners, it's at the apex. scarey devil smiley



Edited 1 time(s). Last edit at 2009-12-23 01:11 AM by GLA72.

NOHOME P P
O, ON, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
The gearboxes are probably the worst thing about these cars. They are also pricey to do a proper re-build since this will include a new laygear. If you dont believe in mixing new and old gears, then you will end up buying pretty much all new internals.

Pete

mgbgts Avatar
mgbgts Rob Meier
Johnstown Ohio, USA   USA
The gearboxes are fairly robust, but not nearly as bulletproof as say the 68' and later MGB boxes. but as for the 1500 boxes They are NOT better than the earlier ones. I have a friend who makes a living rebuilding Midget gearboxes, and he see's plenty of 1500 boxes. The biggest problem is they are now at least 30 years old (35 years for the pre-1500 boxes), and were not always kept full of oil.

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Billm Avatar
Billm Bill Masquelier
Santee, CA, USA   USA
Easiest and least expensive fix for a gearbox is to put a Datsun 210 4speed in it. The 5speeds are really nice but the 4speed trannys are pretty cheap.
Often the change to a Datsun gearbox is less expensive than having yours rebuilt
I an in Renton, where are you?
BillM

zedvictor1 Avatar
zedvictor1 Steve L
Albion, WA, USA   USA
I'm in Spokane, Bill.

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jvandyke Avatar
jvandyke Jeff Van Dyke
Hudsonville, Hudsonville, MI, USA   USA
We've been discussing it here over here too:
another forum

My 1500's box was problematic (a '75 Midget in 1989 so not horribly old at the time) It's replacement was also problematic. My ribcase has been too but it was run bone dry!



Edited 1 time(s). Last edit at 2009-12-23 10:30 AM by jvandyke.

appysforme Ian Repay
Edmonton, Canada   CAN
Just wondering how to tell if the gearbox is low on oil? I have added 20W50 oil ONLY to the gear box but I never know when to add or when it is low? Is there any way to tell other than just removing the bolt and adding oil until it leaks out? This is a very messy way to know when the gear box is full.

Billm Avatar
Billm Bill Masquelier
Santee, CA, USA   USA
You need to join us (next spring probably) at the next NOSHIT get-together here in the Sound area. It is just an informal work-party to get all of the local cars running (and BS a lot!).
Bill

7mg2 Avatar
7mg2 Andrew Hardie
Calgary, AB, Canada   CAN
1969 MG MGC GT "Mr "C"
1972 MG Midget MkIII
Ian,
you have described the only way to check the level in your rib case box that I'm aware of. I suppose a dipstick of some sort could be devised to avoid some of the mess, but if you're anything like me, it would get misplaced between dippings.:moody: On the bright side, if you have no significant external leaks, checking the level is a chore that does not have to be performed all that often.:thumbup:

I now have a Datsun 5 speed in my car which was an awsome upgrade, but I had many reliable years from my rib case. I just wanted the overdrive which the 5 speed gave me. The synchro 1st was a bonus that I would find it hard to do without now, so the 4 speed mentioned by Bill makes some sense too.

Merry Christmas.:beer:



Andy

NAMGBR# 20-7738
AMGCRA# 1678

200mph Avatar
200mph Platinum Member Mike Joy
Winston-Salem, NC, USA   USA
Stephen,

Bryan pretty much nailed it above, but let me add one thing.... do NOT spend the $$$ to rebuild your gearbox...

In the northeast and northwest, many Spridgets ferll victim to the tinworm (rust) early on in life. That means there are hundreds of used gearboxes lying around with no home. You should be able to find a good used one ("running when parked"winking smiley for $100 or less. Its hard to get a good mechanic to even open up your box for that and look at it.

Get a used box or two, buy one of those $99 engine hoists from Harbor Freight, and get to work. You can wear out half a dozen used boxes before you begin to approach the price of a rebuild.

bleteaches6 Avatar
bleteaches6 Silver Member Lee Orphan
Bonney Lake, WA, USA   USA
In reply to a post by Billm You need to join us (next spring probably) at the next NOSHIT get-together here in the Sound area. It is just an informal work-party to get all of the local cars running (and BS a lot!).
Bill

Where do you meet Bill?

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