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MG MGB Technical - Rivergate/280zx 5sp transmission

I am looking at doing a 5sp conversion using the Rivergate kit. The transmission was made with two different 5th gear ratios. The early ones were .864 in 5th gear and the later ones were .78 in fifth. I have located one from a 81 280zx that should be .78 fifth gear. Are there any codes or other identification that would help in identifying if the trany was the one with the .78 ratio?
Jim Lema

Jim- Sorry, I have no info on final ratios, but do have some questions to bug you with if you don't mind:
1. What finally brought you around the Nissan swap over, say, the Ford Sierra 5 speed?
2. I've heard the 280-Z trans shifts like a dream but tend to pop out of 2nd and 3rd under compression in some downshifts. Myth or true?
3. Some say a full 10 inch radius pressure plate is required and can be easily provided by using a TR pressure plate, yes?
vem myers

vem

1. I can get a Nissan box for less than $200. Sierra boxes are hard to find.
2. Not heard about any problems with the box, it is basically a Borg Warner box.
3. Rivergate site says it uses standard MGB pressure plate. I plan to ask them several questions that relate to what I have done to my car, will ask them about pressure plate at same time.

Jim Lema

I have the Rivergate 5-speed conversion in my '73 and couldn't be happier. It shifts wonderfully, and after about 2 minutes feels completely natural.

Jim, I don't know about particular markings either - you may check the local Nissan dealership, but be prepared for them to ask YOU for the information you need from THEM: Year/make/model/etc. Your info about gear ratios is correct, by the way. I've got a transmission from an '83 ZX that has the .78 5th gear. This is great on the highway, and not needed in hilly twisties.

For myself, I chose the Rivergate kit because I got a wrecking-yard transmission for $125. Add in another $200 to have it inspected and serviced and you can't beat it. I've had no problems at all with it popping out of gear under any conditions. The only quirk is that 1st and 3rd are physically very close to each other and it doesn't just slide into 3rd. Easy to get used to, and it winds out nicely all the way up.

I used the standard MGB pressure plate, but a Jensen Healy clutch cover (part # GCC139). The original instructions said to grind down the MG clutch cover but the JH part fits perfectly. I've passed that info along to the good folks at Rivergate, but don't know if they've incorporated it into their instructions.

R.
Rick Stevens

I am running a transmission from an 81 myself with the rivergate kit. You do 70mph around 3,OOO RPM. 75-80 MPH no problem. Cruising at 55 turns about 2300-2400 rpm. In the twisties just use 1st - 4th like normal.
55mph in 4th is around 3000 like normal. By the way....where are you guys finding z boxes for under $200 and who do you have check them out.....I cant find many around here, then the people who have them are very proud of them.
Bryan

In many parts of the country there are a growing number of salvage yards where you pull off your own parts. Ours locally is called Pick-N-Pull and I think is part of a chain. Two of my fellow club members just picked up two Nissan 5 speeds from there for under $100 each and still have to get a couple of junk transmissions to get their core charge back. They can be found pretty cheaply, but you have to look and be prepared to get your hands dirty, which shouldn't bother most of us here on the board. We've also found two MG o/d transmissions there over the years as well as a lot of other pieces such as MGB A/C systems and SUs to convert later model Bs.
Bill Young

Rick,

I keep my eye on http://www.car-part.com/index.htm for lots of used parts. It's a pretty neat resource.

FWIW,
Allen
Allen Bachelder

Allen, thanks for the link. Now I'M keeping an eye there. ;)

I also got my 5-speed from a Pick-N-Pull, for about $125. This one was serviced at a Mom-and-Pop transmission shop in Monterey.

Rick Stevens

Hey Rick- I can grab a rebuildable 5 speed in San Jose. Would you recommend the Monterey rebuilder? May I ask how much you paid and for what? Thx, Vic
vem myers

Vem, I'm not sure it would be worth the trip down to Monterey unless you spend enough time on that side of the state. The place I went to was Quality Transmissions on Del Monte Boulevard in Seaside. It's a small shop, pretty unassuming, but the owner seemed okay - and I don't have any complaints at all about the work.

Basically, all they did was to clean and inspect the tranny, putting in new front and rear seals. Plus, he fabricated a new shim for the shifter since the original had broken somewhere along the line (it had a lot of play when I took it in, and none now). Mechanically the box was perfectly sound, so it didn't need any real work done. I paid just a bit over $200 for the service. Maybe a bit high for peace of mind, but a heck of a lot cheaper than finding a problem later. Considering that most of that was labor costs, I think I got a fair price for the work.

I've put about 3,500 miles on it since it was installed and have no complaints at all. It's a LOT quieter than the stock 4-speed and feels 100% natural. Also, to date it's not leaking. Now how cool is that? ;-)



Rick Stevens

Vem...I had a 1978 Datsun 280Z with 5 speed. I NEVER had any problems with the drivetrain....period.
rick ingram

The story of 280Z trannys coming out of gear is a complete myth - probably from one individual who had problems and complained a lot! Mine works flawlessly! I use an MGB pressure plate in mine, along witha 280Z slave modified for use with a stock MGB stainless hose and a Wilwood 5/8" clutch master. Its a great package with better 1st and 2nd gearing. I have the later tranny with a deeper 5th gear too. I think its .74 from an '83?
Jeff Schlemmer

Jeff- Great info and clarification. For me, it is invalueable to air a myth and get user testimonials busting it. I have often suspected, article writers, and even on levels like this, too much is fabbed or assumed to fill a word quota or "flesh" out a tech article: The user articles on the "Click-It" valve adjuster come to mind. To get a testimonial from Jeff a known and solid entity, is to give me "hard data". Thanx, ol son. Vic
vem myers

Jim & others, I have been doing the 280 Z 5sp. for over 10 years & talked & bought parts from Rivergate. The only prpblem that I see with this package is that NO ONE put a great package together like Rivergate & I do. I have sold 25-30 units (sold Mr. Jeff his) & I have not had a problem. I have driven my 74 G.T. over 90,000 miles & all I have done is change oil in the trans. If you think you would like to drive one ask around, they are out there. What I do is cut a 280Z disc down to 8.5 inch to match the B pressure plate, there is no way you can put a 10 inch cluch in (B.V-8 used 9.5) I think thay went to the .78 5th. in 1980. Good things about the Z box is 1, lighter (30 lbs I think) 2 ROLLER T.O.B. !!!!!!!!! 3, Can pull out from under the car & I have changed the engine rear oil seal in 3 hrs. (top that with your O/E trans.) 4 Alu. backing plate 5. Shift spread between gears is nicer. Best thing you can do to a B, for the buck! I have been told by people that have bought the Z 5sp. package from me.
Glenn Towery

Hi Glenn- Didn't we chew the rag a bit on this a few months ago? How much is your conversion, and I recall you do include a rebuilt box, recommend a 10 inch pressure plate ( TR-8), s-bend the shifter to place exactly as stock in console, and pledge to supply "every nut and washer " needed. Cheers, VEM ( OTRA)
vem myers

This thread was discussed between 11/11/2007 and 29/11/2007

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