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MG MGB Technical - Overdrive Rebuilder Recommendation?

I need to get a D-Type overdrive unit rebuilt. Is there anyone closer to the Los Angeles area than Quantum Mechanics who are qualified to do the work?
Steve Simmons

Steve,
Have you given any thought to doing the rebuild yourself. I've attended two John Twist seminars where, under his watchful eyes, rebuilt three OD transmissions. The transmissions still scare me a bit, but I found the OD units quite simple to disassemble, refurbish (clean and replace O-rings) and reassemble. The only difficulty encounter was fitting the OD unit to the rear of the transmission. John had to do it for me (this year) and it took him a number of tries. My son was with me this year doing a separate (second) OD transmission and he experienced the same problem, as well. I don't think I would ever attempt OD to transmission attachment under the car. Parts costs for three OD units were less than $100 each - guess I was lucky.

For a recommended local rebuilder - suggest contacting either John Twist (University Motors) or John Esposito (Quantum Mechanic). They may know of someone.
Steve Buchina

Steve,

I second the John Twist option.

Paul
Paul Hanley

Well that's a bummer to hear! I was planning to remove just the OD unit and send it for rebuild, then reattach it myself. I thought that would be the easy part! Guess I should send the whole thing in. I don't think I'll try it myself. This OD unit has seen some abuse so I want it thoroughly checked out by someone who knows what they're doing.
Steve Simmons

Steve,
Found the following on ebay.

3 synchro MGB convertible/GT overdrive transmission
Item number: 150093996765

The starting bid is $950 with a "Buy It Now" price of $$1,100. Unit requires some reassembly and no warranty, so price may be a bit high. What caught my attention was this seller refers to "a great shop" close to him. I don't know where Redding (CA) is, but it might be worth checking out.
Steve Buchina

Hi:

Two key items regarding D types:

1) If you don't know the units history; then a complete rebuild is required to prevent overdrive roulette. Rebuild must include all ball bearings, new seal kit (o rings), rear seal, speedo seal, gaskets and cone clutch.
2)Other parts as necessary if the unit fails a bench test. These units must be tested before reinatallation to the car, to prevent overdrive roulette. Visual inspection of the cone clutch is misleading, the materal may look great, but will shatter under heat and pressure after rebuild. I usually buy the VB kit for approx $100 and have John Esposito at Quantum do the rebuild, new cone clutch, clearencing and bench test

Good luck: Rich Boris. 67B roadster
Rich Boris

Steve,

Reinstalling the o/d unit on the main case is not that hard. There are little splines inside the o/d that must be rotated to line up with the rear tail section. A flashlight and a small screwdriver does the trick in no time flat. Send only the o/d unit to John Twist for a better than factory rebuild.

Paul
Paul Hanley

Steve, thanks for the lead. Unfortunately that's a bit pricey for an unknown condition unit! And I already have one here anyway.

Rich, a complete rebuild is definitely planned. I do know the condition of the unit and it's not good! There were a couple pieces of gear teeth in the bottom of the transmission housing so I'm sure the oil was well contaminated with metal dust. Then it sat outside for quite some time before I found it.

Paul, I'll keep it in mind. I'm planning to install the OD unit to a non-OD gearbox because the non-OD unit was very recently rebuilt using new gears and was modified for a later (larger) input shaft with dual bearings. Early gearbox, late model durability! I may have to change the output shaft if I understand correctly so I may or may not attempt this alone.
Steve Simmons

Steve

It is a bit far, but our British Car Club has a super OD transmission rebuilder. He works on just about every Laylock they made.

He charged me $400 plus parts. Unit comes back with a guarantee of no leaks and he does a bench test run of the unit for 4 hours.

I can send his name and email if you are interested.

Bruce

Wisconsin
BEC Cunha

Steve wrote:

I'm planning to install the OD unit to a non-OD gearbox because the non-OD unit was very recently rebuilt using new gears and was modified for a later (larger) input shaft with dual bearings. Early gearbox, late model durability! I may have to change the output shaft if I understand correctly so I may or may not attempt this alone.

Steve--not! Can't be done. You need a 100% disasembly of the gearbox to recover you new parts. The third motion shaft--the output shaft--is different onthe o/d box.

For your engine to accept the larger input shaft, you'll need a different crankshaft.

Paul
Paul Hanley

The crank shaft already accepts the larger input. This transmission has been in the car for some time. I just want to add OD to it.
I knew I had to change the output shaft, but I didn't realize it was a complete disassembly. Bummer! I guess that's the decision right there... I'm not doing this myself.
Steve Simmons

Steve,

Chris Betson (http://www.octarine-services.co.uk) sells a a kit to convert 4 sync non OD boxes to an LH OD box. I don't know if he could do a similar kit for a D type with a 3 sync box. Either way, there are comprehensive instruction for the conversion on his site. It would be worth reading these so you can grasp what is involved in changing a non OD box to an OD box, even if it is not directly relevant for your box and OD.

In the UK if I was getting an OD rebuilt I'd either send it to Chris or to http://www.overdrive-repairs.co.uk/products.html There D type exchange unit is £200+VAT (17.5%) or about $460. No idea if shipping the OD back and forward to the UK would make this impractical, and it still leaves the probelm of converting the box!

Anyway, have a read of the directions on Chris' website.

Cheers
Iain
67 BGT
I D Cameron

Actually, thinking about it the easiest way for you to get an OD box might be to buy an unknown one, transfer the parts from your rebuilt 3 sync box and get the OD unit rebuilt. With the differences in the case I'm not sure how easy it will be to convert! In the UK you can get an unknown 3 sync OD box for about £300 on eBay, but they are fairly rare (maybe one a month?).

You'll also need a different drive shaft or a spacer for your current one as the OD box uses a shorter drive shaft and the speedo is also different (small percentage).

Iain
67 BGT
I D Cameron

Hi:

For a 3 synchro non O/D to O/D conversion; you essentially need a donor O/D gearbox; less D type if you have one. The differences between the gearbox is as follows:

* 3rd motion/Main shaft is different
* O/D extension adapter is required
* O/D shift tower is required
* interlocking arm/gate is mirror image for the O/D configuration, you can't use the non O/D gate.

I have tried to buy these required parts individually, and no one will sell them, or they want a small fortune. Best bet look for a complete 3 synchro o/d gearbox and sell the extra D type to reduce the cost impact.

Good luck: Rich Boris 67 B roadster
Rich Boris

I have a complete 3-sync D-type OD gearbox. But my non-OD box is freshly rebuilt and modified for the stronger input shaft. That's why I'm planning to do it this way. It sounds like I have all the parts I need but I'm investigating it further.
Steve Simmons

A couple of years ago I spoke with a rep from
Gear Vendors from El Cajon, CA.

He said that they were looking into rebuilding
the Laycock ODs as part of their business
...some day.

You might try and ask them if this ever came
into being, or if they can recommend a local
rebuilder.

www.gearvendors.com
Daniel Wong

This thread was discussed between 21/02/2007 and 24/02/2007

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.