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MG MGA - 4-speed vs. 5-speed

I've owned my MGA for a little over a year and already love it more than the two MGBs I had for over 15 years. But the previous owner installed a Nissan 280z 5-speed transmission (which I dislike, doesn't feel notchy or "british") and wedged it into a smaller tunnel which vibrates terribly at 4000 RPM. Doesn't seem to be any room to bash it out further, so I may be replacing the tranny soon, vibrations are so bad I think all my screws are coming loose :)

Question for other owners: what advantage do you see in a 5-speed, aside from comfortable cruising at 70mph? Is there any other difference in the gearing? Could you live with the original 4-spd if you kept your top speed to 60 mph on the highway, even for several hours at a stretch?
Jim P

For me Jim, in Southern California, being bound to the slow lane for 20 years was torture. Driving a car that looks so fast makes it worse. O.K., I always have been a speed freak. I'm doing better now, honest, I can slow down any time I want.... But I am much happier now with my 5-speed in the fast lane, or at least knowing I can go there if I chose. The Ford unit has been like butter and its virtually a bolt-in. I don't miss the British corseness or the 2ed gear syncro which would never last. Either way, happy to hear your enjoying your A, they sure are fun.
Steve
Steve Meline

My sugestion is increase the power of your engine by about 10BHP and change the diff ratio. to 3.9 or 3.7
Then you still have an MGA.

I too have a datsun 5 speed in my B GT. horrible thing.
Mark Hester

Truth of nature #1: Conversion of MGA to OD or 5-speed is not necessary to make it go fast and can never be economically justified. It is a luxury accessory until such time as you may modified the engine for more than 110 BHP output.

If you increase engine power output above stock configuration, the primary concern should be not to blow past red line in top gear. This may of course depend on you driving circumstances. Overall final drive gear ratio is related to red line thusly:

4.3 = 102 mph @ 6000 rpm (std 1500/1600)
4.1 = 107 mph @ 6000 rpm (std. 1622)
3.91= 112 mph @ 6000 rpm (std 1800)
3.7 = 118 mph @ 6000 rpm (special)

Using numerically lower gear ratio reduces engine speed and also reduces torque at the rear wheels. If the engine does not have enough torque to pull it, then it will not reeach the highest possible speed in top gear.

If you install OD or 5-speed, and your engine doesn't have enough power to pull top gear to top speed, then you should change the final drive gear to pull top speed in 4th gear and use 5th or OD strictly for quiet cruising.

If you install a fast street cam or big valve (or ported) head, drop the ratio one step.

If you install a fast street cam AND big valve (or ported) head, drop the ratio two steps.

If your warmed over engeine exceeds 110 BHP, then you may need OD or 5th gear to stay under red line at full chat. If you don't need it you might feel rich and want the luxury anyway. My preference would be 5-speed for simplicity of installation in the MGA. Apparently the Ford 5-speed is the better choice over the Nissan unit.

$.03
Barney Gaylord

Another way to tackle it - just drive at whatever speed traffic dictates - I have run for hours in the 80 MPH range in an MGA with 4.3. These engines will run all day at 5000 RPM - it doesn't bother them, why should it bother you, except for a slight bit more noise, but at 80 MPH there are lots of other noise.

Is my MGC, which will lope along at 100 MPH at what would be a fast idle on the MGA more comfortable at that speed - sure, a bit, but the MGA is also fine.

I met one MGA owner that told me he never exceeded 4000 RPM in his car - felt like saying ya gotta LIVE, man.

A stock MGB engine in an MGA will support a 3.9 diff, which of course is longer legged than the same diff in an MGB with 14" tires.
Bill Spohn

which Ford 5-speed trans???? from which Make, model, year, etc... is this trans readily available??? I have heard that by changing out the rear-end to a 3.9 without the added HP is not the way to go??? I have a 1958 MGA that is bored 30 thousands and the head milled, electronic ignition and webber carb.. I'm sure this doesn't boost the HP much at all. I would also like to stay up with the truckers on I-80 heading toward Chicago.. I won't change the engine to a 1800. Mike
Mike

Mike,
Ford Serra I think is the chosen one.
lots of info here.
http://www.hi-gearengineering.co.uk/frames.htm
search the archives and you will find heaps of info.

If you fit extractors to your's then you can't be far off 10BHP or more anyway. Depending on webber jetting.

I had a stock 1500 with 45 weber & extractors and it had easy 10 BHP more... untill the crank broke that is. Oh, 18v pushrods and followers also (1 BHP maybe)

Most cars today have lower profile tyres which drops the gearing anyway.

Your speedo will be out if you change the diff ratio and also out if you change the gearbox.

Maybe your webers not setup correctly.
I put together some weber settings here.
http://freespace.virgin.net/marka.hester/RaceStuff.htm

Cheers <MARK>
Mark Hester

I think the diff in my car is 4.1 (1962 mark II) and it is too sluggish from a start...not enough torque for the Nissan transmission. Ya gotta wind the engine way up high in revs before engaging first gear. Then when you do, it still feels sluggish. I'm hoping that returning to the original MGA 4-spd will cure my problems. Also original A gearboxes are way less expensive than the Ford 5-spd or an MGB overdrive conversion (which I would love).
Jim P

Jim:

I run my box stock 1500 with original 4 speed and a 4.3 rear end at speeds of 60 to 70 mph for hours on end all the time. Yeah, it makes lovely music at those speeds and it will be turning around 4000-4200 RPM at 70, but I'm with Bill on this one, I don't think that it stresses the engine much at these speeds.

I think that we are so accustomed to modern cars that drone along at 70 in the 2500 RPM range and are so insolated that you can't even hear the motor at all that we get concerned when we can actually hear the mechanics of horsepower being made.

I love it!!!!

Clayton
C. Merchant

Sorry, that should have been insulated or isolated, but not "insolated".

C
C. Merchant

I have a 3-main 1800 on a stock MGA 4-speed transmission. I run all day at 80MPH+ in 4th gear with no ill effects. I've been doing the same in my MGB for 17 years.
Steve Simmons

Jim

Why the vibration? No one has addressed this but I wonder if something is "not quite right" in the drivetrain. Maybe a drive shaft that is out of balance? U-joint?

Where are you in California? What year A? I have an extra early A transmission and might be interested in a trade if you pull the 5 speed. Contact me off line if interested.

Larry
58 A
San Diego
Larry Hallanger

Jim, I think Larry's on the right track, find the cause of the vibration. I wouldn't think the transmission was the cause, more likely a u-joint or driveshaft. One of my fellow club members just installed the Nissan trans in a B last year and loves it, so I'd think you might like it better once you find the cause of the noise and vibration. Everyone I know who has installed a 5 speed, either in a B or midget is more than pleased with the installation, so your experience is interesting.
Bill Young

Just completed 5 speed Nissan conversion to a 3 main B engine, with a 3.9 rear end. I have not experienced any vibration with this conversion which I completed last month. You may want to check the clearances on the transmission tunnel, as I had to reshape the tunnel about 1" over to the passenger side, near the front. I don't miss the noise at high rpm's, and the lack of first gear syncro. I would do this all over again!!!!!
cliff hughes

According to my mechanic the transmission is wedged so tight against the tunnel that it is touching all along the passenger side. This has gotten progressively worse over the past year and now is almost intolerable. I had a female passenger liken it to a vibrating Barcalounger (remember those?).

He claims there may not be enough room to bash the metal out more. This is a mongrel tunnel since there is no "camelback hump" like most MGAs have...mine is lower. I suppose I could find a new tunnel. But mine is NOT the "Rivergate" conversion, it was done long before that was available and it was sort of a hack job. Hey Cliff where did you get your tunnel from?

You can see pix on my site
http://www.jimpaul.tv/mga
Jim P

Mark- What I think Mark means is, what car in the USA used this trans since we never had a Ford Sierra here. I have heard that a Merkur XRi was the same but I'm not sure. Anyway what you are looking for is a type 9, anyone have any idea? Gary
gary starr

Sorry I wanted to say what Mike means
gary starr

Jim P. I used the original tunnel, and with a ball pein hammer, beat the tunnel on passenger about 1" to 1 1/2" along a 5" section just in front of the emergency brake handle. I then covered the tunnel with carpet backing and new carpet. This procedure of beating the tunnel was completed from under the car. We then checked the length of the tunnel for drive shaft clearance. Had to fabricate a new rear transmission mount, as the original was cut to allow for easy removal. I had to cut 1 1/2" from the top of the gear shift lever to allow for a better fit. I also had a problem with the Lucas starter, so I converted to a Hy Gear starter, as it takes up less room. It sounds like a Japanese car when it starts, but so what. It has not lost any MGA sound when travelling down the highway. I plan on driving it to Gatlinburg in June for the MG event. Cliff
cliff hughes

Jim, if you want to go for a ride in my A, feel free to give a call.
Steve Simmons

Mike P. The reason for installing a 5 speed Nissan transmission over the Ford Sierra type, is the more readily available Nissan. I paid $85 for the Nissan tranny at a local wrecking yard. I had to take it out, but that took only 45 minutes. Cliff
cliff hughes

Back to Gary's question: It would be helpful to get more information on the exact USA source car for the type 9 trans. And also which type 9. From what I have seen online there are at least two different type 9s. Can anyone supply this info.

Jon
J.T. Watson

Jim,

Nice car; nice site.

JOe
Joe Cook

Back to my original question. Which Ford in the USA can one find the Ford Sierra type 9, 5-speed transmission??? the only Sierra I know of is the GMC Sierra pickup truck... Mike
Mike

In the US ths Ford Type 9 gearbox was used in the Mercury Mercur XRi. This car had engines of 1.6L & 1.8L: 1982-91, & 2.0L: 1982-87.

There are at least three different gear sets available. See here: http://mgaguru.com/mgtech/gearbox/gt402.htm
I do not know for sure which gear set was used in the US Mercur, but I suspect the {"standard Ford" arrangement (not modified or close ratio).

There is a detailed description eith pictures of an installation here: http://mgaguru.com/mgtech/gearbox/gt402.htm
Barney Gaylord

Gary

Check both the A and B archives as this is discussed in detail. As I remember the type 9 has 2 different output shaft lengths. The one that works without modification is from the XR4Ti. Track down Frank Murch in the archives on the B board. He installed one that I originally got out of a salvage yard. I thought I had the correct shaft length but when he went to install it I believe he had to modify the shaft to make it fit.

THT

Larry
58A
Larry Hallanger

This thread was discussed between 14/03/2006 and 15/03/2006

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