MGB: transmissions

I realize that there are many past discussions about 5-speed conversions and O/D options, with adequate links to sources for both, Rivergate, Acme Speed Shop, Moss, Quantum Mechanics, Octarine, and more. Both options have their supporters, as well as some who see no strong need for either. This leads me to believe that those of us wanting to drive at freeway speeds more comfortably can't go wrong with either the 5-speed or the O/D!

So I am looking at my options from a strictly financial perspective. My recent research with all of the aforementioned sources seems to place the T-9 route at the top of the cost list (read that "most costly") and, I think, the O/D at the bottom (assuming you have a solid 3-syncro box), with the Datsun Z somewhere in between:

Acme Speed Shop T-9 transmission $2,775 plus shipping, plus cost for installation
Rivergate 280Z transmission $2,200(approx) for box and conv. kit plus $550 installation by them
Octarine O/D conversion kit $1,100 delivered to US plus converting and installing

You actually can spend more on each option, but the best that I can deduce, the above are the least costly for each, so far.

Since I do have a solid 3-syncro box in my '66 B Rdstr, I am finally getting to my questions.

1. Would I need an MG "savy" transmission person to do the conversion work?
2. Does anyone have an experienced estimate of the cost for takeout, conversion, and reinsallation?

Look forward to the forum's coments.

John

I have done the t-9 from Quantum Mechanics. There is very little "conversion" work except the input shaft bushing. Everything else I remember is no different than a remove and reinstall of a standard B transmission. You are not getting inside the box.

This would put in on par with a straight OD swap, which I have done as well. Unfortunately the motor will have to come out to get the standard B transmission out. The T--9 can come out without removing the motor for the future.

[quote=txmgb]

1. Would I need an MG "savy" transmission person to do the conversion work?

John[/quote]

Yes, definitely, unless you are a fairly skilled mechanic and willing to try it yourself. Be warned though, you can hit problems, two local guys, both members of this forum, have been building overdrive transmissions from "kits" recently. One of them bought two overdrive units plus the mainshafts from the UK and converted two transmissions with no problems. Another guy is trying to do the same thing but the gear set from his 4-speed will not fit on the O/D mainshaft, apparently this is very rare but it can happen, he's probably going to have to find another transmission to work on.

I had a 3-sync box converted to OD by Quantum a couple years ago. I sent them my complete gearbox plus the conversion parts I removed from a donor box. They performed a complete rebuild and conversion and shipped it back to me for around $850 if I recall correctly.

You can do the work yourself but it isn't what I would call "basic mechanical skills". You need a fairly decent understanding of how this stuff works if you want a solid chance of everything working when the car hits the road. If you have the time and patience and are willing to risk having to pull it out of the car again then by all means give it a shot! Just my opinion of course.

$1100 seems pretty steep for a conversion kit since you can buy a complete D-Type gearbox for a few hundred and then have it built. Then again I'm sure the parts that Chris sent will be top notch and in perfect order.

Firstly, for $2k it’s not worth it to go to OD. The car works just fine with 4 speeds in my opinion. Its probably not good value for money.

With that said, I am doing the Rivergate Datsun kit it’s going to cost me just over $1k.

If you're game for spending 2k on the car, I think there are a lot of other cool things to buy with that money. You can get a good OEM electronic OD trans for $800 bucks, or a good core for $500. I would probably have done that if it wasn't for the fact the Datsun box is a wonderfully designed transmission. I found one with the close-ratio gear set, and the tall overdrive. I drive a GT, fast, and I need something that can take my relentless punishment.

my .02

Converting a 3 synchro box to OD can be pretty involved but simply installing an OD transmission is probably the most straightforward option. Unfortunately you just missed one on e-bay for under $400.

A Datsun box can usually be found for about $350 and they are robust enough that there's not a need to tear them down and rebuild them if you are reasonably selective in picking one. Plus the kit and misc pieces the package should be closer to $1500.

Well, of course I would like to find a GOOD O/D unit that would be the right one for my '66 for $800 or less.

Would any year model unit fit ,or do I need the one that was the option in '66?

If you get a 280z box, there is one bearing that needs to be replaced. It's undersized and the later transmissions had one that we beefed up. Its the front layshaft bearing.

Personally, I would choose to dissasemble and clean/rebuild any used transmission. The reverse gear does not have a lock-out feature on the early 280Z boxes, 80% of the time the reverse gear is chewed a little. Sometimes you need to get a new gear. Sometimes you need to get two new gears!

If anyone wants, I can provide the service to rebuild any datsun 5-speed transmissions for low cost. I can source core transmissions as well.

My last comment is: If you're low on cash, go with the MGB OEM overdrive. If you have money to burn, go with the datsun kit. I don't really like the t-9 transmission too much, so I would lean to the Datsun camp. The T-9 coversion its a REALLY SLICK kit, but I perfer the design of the datsun gearbox.

If you can change a engine/gearbox, you can do the T9 kit, it's a straight in bolt up. If you're paying a professional shop to do this for you, expect to get hit with about 7-10 hours at whatever their labor rate is.

The T9 kit is pretty stright forward, and the least "modifed" of the bunch meaning you use a stock unmodified MGB clutch (including clutch disc), flywheel, throw arm and bearing, and slve cylinder. basicly they made the bolt bellhousing that attaches to the T9 to be a excact coopy of the front of a MGB transmission case, so everyhting bolt up clutch wise just like it would in a MGB, under the hood, it even looks like a stock MGB transmission, this appeals to alot of folks when looking at the kit available. Te T9 kit aslo come set up for either the earlier (3 syncro) car or the later (4 syncro) cars, so in the future you'll only need mgb repalcement clutch parts, no special or modified parts.

The T9 is also a very nice gearbox, I had several cars fitted with the T9 in the UK and I loved the feel of it, beautiful, slick shift.

[quote=txmgb]
Well, of course I would like to find a GOOD O/D unit that would be the right one for my '66 for $800 or less. Would any year model unit fit ,or do I need the one that was the option in '66?[/quote]

You only need the correct, larger input shaft. '62-'64 were smaller than '65-'67 (and later 4-sync boxes). I have a couple of complete D-Type gearboxes here that are correct for '66-'67, one which I'm planning to remove the OD unit from and get rid of the rest. I would certainly consider the trade of a complete gearbox for a conversion kit since that's all I need anyway. Your kit, being new, is probably worth more than a complete used gearbox however. If you want to entertain the idea then we can certainly talk about it. I have a spare vacuum switch (very hard to find) that could sweeten the deal a bit.

Steve,

I have not yet purchased a kit. Just trying to weigh my options, because I am definitely going to do something, either the Riverside Datsun or do an O/D upgrade to my existing stock box. Partially a financial decision, partially a "path of least resistance" decision!

Always appreciate your input.

John

Whoops, I'm not sure how I misread that. I think I just confused two threads from completely different forums! :eyeroll: