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tips, technology, tools and techniques related to vehicle driveline components

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jblanchard@hcpg.net
Jeb Blanchard
Collierville, TN
(52 posts)

Registered:
12/07/2007 01:01PM

Main British Car:
1961 MGA Chevy 4.3 Vortec V-6

authors avatar
Automatic or Standard Transmission in 1961 MGA
Posted by: jblanchard@hcpg.net
Date: January 02, 2008 04:22PM

Automatic or standard transmission comments/suggestions??

I do not have the patience or ability to do my own mechanical work. Iíll spend hours blocking, wet sanding, buffing; no problem. Someone else completes all fabrication and mechanical work, but I do my homework and am heavily involved in the build process.

The car was built with a 5 speed Chevy transmission (30% over drive), and a 3.08 10-bolt Chevy rear end designed primarily for an automatic transmission. The builder bought the transmission on good faith and we found the 4th gear sychro was going out, so I bang in 4th. Also, an extension to the shift knob had to be fitted which causes shifting problems. Since we have to pull the engine and transmission, now is the time to make a change. One of the reasons I do not like the present configuration is that I do not have power in 5th gear below 60 mph. Iím turning 2050 rpmís at 70 mph.

The engine is a Chevy 4.3 V-6 turning out approximately 300 horsepower. Iím inclined to go with a 700r4 (with lockout) transmission, provided we do not have to extensively modify the transmission tunnel. Until now I have been of the opinion, ďIf you ainít shifting you ainít driviníĒ (Iíve owned two standard domestic autos, two MGBís, and an MGA. I realize that I can change the gearing in the rear end to correct low power in 5th, but Iíve heard good things about the performance of the 700R4.

Any suggestions, comments?


Citron
Stephen DeGroat
Lugoff, SC
(365 posts)

Registered:
10/23/2007 09:43PM

Main British Car:
1970 MGBGT V6, 7004R, AC, matching trailer 3.1 liter

Re: Automatic or Standard Transmission in 1961 MGA
Posted by: Citron
Date: January 04, 2008 10:25AM

Jeb,
I run the 700R4 in my BGT with a 3.1 , stock engine. I really like the trans. I have a manual lock-up switch. I can lock the torque converter in 2nd, 3rd or 4 th. I have the stock 3.9 rearend, but am working on a Ford 8 inch with 3.0 gears.
Now I run 2900 at 80 mph, with the 3.0 it should be about 2200. I travel alot with it, so the gas mileage is important.
My trans is stock, except for a kit so it will rum at full throttle in 4th. Before that it always kicked doen to third.
The trans and engine have about 125000 miles on them and are doing fine.
I do not know if a stock 700R4 will take 300 hp.

Good luck
Steve


V6 Midget
Bill Young
Kansas City, MO
(1337 posts)

Registered:
10/23/2007 09:23AM

Main British Car:
'73 MG Midget V6 , '59 MGA I6 2.8 GM, 4.0 Jeep

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: V6 Midget
Date: January 04, 2008 02:09PM

Jeb, I think you'll find the auto box a bit large for the MGA and would require more trans tunnel mods. I'd say stick with the T5, fix the shifter problem which shouldn't be difficult. I was able to shorten the shifter in my Midget, weld a fine thread bolt that matched the MG knob on the stub and haven't had any problems and it shifts slick. The real problem is the rear axle ratio. You would probably be quite happy with either a 3.23 or 3.43 ratio, both are pretty common in GM S-10s and Camaros. I'd get that changed before I changed the transmission. To help determine what gear would be best here's a handy gear calculator that I like.
[www.f-body.org]
As you say, there's nothing wrong with the auto box, it just doesn't seem like a sports car to me if you're not shifting the gears manually.


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: Moderator
Date: January 04, 2008 03:26PM

Jeb, you may have already seen this but here's a direct link to more info about T5 trannies, including gear ratio charts: [www.britishv8.org]

I'd love it if someone would volunteer to add a column or two to this chart so we could easily tell how far back the shifters are from the bellhousings, etc.

Wouldn't a longer dimension back to the shifter help you a lot?

Here's another link to a gear/rpm/speed calculator: [www.britishv8.org]
(This is the one Dan Masters created.)

I prefer shifting gears manually... and a manual box just seems to suit a fifty year old sports car. But honestly, on a twisty road or a racetrack - especially an unfamiliar or crowded one - I'm sure I'd actually drive better, safer, and faster with an automatic.

Strictly In terms of appearance, I think an automatic might suit your car pretty well. At a show, most people will be thinking about that cool blacked-out dashboard and your suicide doors. You could possibly even hide the automatic shifter and make the interior look even cleaner and simpler. Doesn't somebody make a retro "push-button shifter" kit for hot rods?


jblanchard@hcpg.net
Jeb Blanchard
Collierville, TN
(52 posts)

Registered:
12/07/2007 01:01PM

Main British Car:
1961 MGA Chevy 4.3 Vortec V-6

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: jblanchard@hcpg.net
Date: January 04, 2008 03:49PM

Bill,

Thanks for your reply.

One of the major problems I'm having is actually shifting gears. The shifter being located so far forward is causing problems. We replaced the stock shifter with a B&M. To shift into reverse you have to reverse your grip on the shift knob, twist it, then hold your mouth just right. To shift into 5th you have to twist the knob and find the gear. It took a while learn to find 5th and not downshift to 3rd.

Changing the rear end ratio would be the only way to go if I stay with the 5 speed. It will be hard to give up manual shifting.

Curtis had an idea about fitting a push button shifter. Do you know if paddle shifters are available.

Attached is a photo of the present shifter configuration.
P1260134.JPG


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5833 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: BlownMGB-V8
Date: January 04, 2008 03:56PM

I'd have to ask where you do most of your driving. If you drive in town a lot the auto makes good sense due to traffic and redlights. But if it is mostly open road the manual should be more satisfying. All the other considerations can be taken care of with either type.

Jim


V6 Midget
Bill Young
Kansas City, MO
(1337 posts)

Registered:
10/23/2007 09:23AM

Main British Car:
'73 MG Midget V6 , '59 MGA I6 2.8 GM, 4.0 Jeep

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: V6 Midget
Date: January 04, 2008 04:03PM

Do you know what car the transmission came from? From the shifter position it looks like it may be a S10 trans which had the shifter several inches further forward than the Camaro/Firebird unit. If that's the case then switching to the Camaro trans would move the shifter back to a managable position. I put a GM 2.8 V6 into my Midget and with the Camaro transmission and the engine not set back into the footwells the shifter came out almost perfect, about 3" behind the stock location. Here's a photo of my car so that you can see the shifter position relative to the dash. It should be pretty close to that on the MGA if you got the engine back against the firewall. I'm using an inline 6 in my MGA and it's notched into the firewall quite a bit, but using a pickup trans with a more forward shifter location puts it almost too far forward to be comfortable.
DSCF0206.JPG
DSCF0032.JPG



jblanchard@hcpg.net
Jeb Blanchard
Collierville, TN
(52 posts)

Registered:
12/07/2007 01:01PM

Main British Car:
1961 MGA Chevy 4.3 Vortec V-6

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: jblanchard@hcpg.net
Date: January 04, 2008 04:49PM

Bill,

You hit the nail on the head. We originally fitted a T-5, but discovered problems and procured a 5 speed from an S-10.

The engine is not against the firewall. We pushed the dash forward 3". We'd considered a 350 but went with the 4.3 V-6 to avoid the extra fabrication. I felt 300hp was plenty for a 2000 pound car.

Here are a couple photos of the position of the motor and another for the position of the transmission.

Thanks,

Jeb
033106 motor.jpg
Transmission 1sf.jpg


Moderator
Curtis Jacobson
Portland Oregon
(4411 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: Moderator
Date: January 04, 2008 05:34PM

Whoa! Is that a New Venture "NV3500" transmission? I thought this car had the short T5 from an earlier S10.


MGBV8
Carl Floyd
Kingsport, TN
(3790 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB, Buick 215

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: MGBV8
Date: January 04, 2008 06:15PM

Like Curtis inferred, that ain't a T-5. Check this site for truck tranny ID:

[www.motivegear.com]

What you really need is a T-5 from a V8 Camaro/Firebird to get that shifter closer to the driver and possibly different diff gears (although the 3.08:1 should be fine if you really have anywhere near 300hp). I would go will Bill's recommended 3.43:1 gears for acceleration & hill pulling in 5th.


Greg55_99
Greg Williams

(98 posts)

Registered:
11/01/2007 07:12PM

Main British Car:


Re: Automatic or Standard Transmission in 1961 MGA
Posted by: Greg55_99
Date: January 04, 2008 07:51PM

That is indeed, an NV3500 truck transmission.

http://www.swbcrawler.com/tech/3550/images/3500.jpg

Greg


jblanchard@hcpg.net
Jeb Blanchard
Collierville, TN
(52 posts)

Registered:
12/07/2007 01:01PM

Main British Car:
1961 MGA Chevy 4.3 Vortec V-6

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: jblanchard@hcpg.net
Date: April 11, 2008 11:40AM

I've decided to go with a T-5 (instead of the 700r4). I've purchased one, and a Hurst shifter, on eBay.

Due to multiple problems encountered on the British V-8 meet last year I'm also replacing the modified MGA front suspension with a custom built Mustang II front end. For some reason I had two new heavy duty MG springs collapse on the front driver's side. The steering linkage had three Borgenson elbows which made steering the A much like a log wagon.

The remanufactured Chevy 4.3L V6 is being replaced under warranty. Nothing like getting 10 MPG and a quart of oil every 100 miles. There was so much smoke I could kill mosquitos at 100 yards.

My driver's side rear end was sagging and screwing up the rear tire clearance. I'm installing AIRoverLeaf's so the leaf springs may be adjusted to stabliize the ride.

I have the same 3.08 rear end and will try this setup. With the T-5 and this rear-end set-up it will have long legs, but they may not be needed because top end speed is not that important. According to the charts, with this rear end, transmission, wheel size, and motor RPMs the chart says it it capable of 210 MPH. Everyone knows that can't (or won't) happen in an MGA. Are there any suggestions for the best rear end gearing?

THANKS


V6 Midget
Bill Young
Kansas City, MO
(1337 posts)

Registered:
10/23/2007 09:23AM

Main British Car:
'73 MG Midget V6 , '59 MGA I6 2.8 GM, 4.0 Jeep

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: V6 Midget
Date: April 11, 2008 11:50AM

Jeb, it depends on which ratio the 5th gear in the T5 is, but from my calculations for my MGA project with the 15" tires it looks like around a 3.30 ratio give or take a bit would be ideal. I can't remember what rear axle you're using right now but with both Ford and GM there are good ratios right around that area that are common. With the higher 5th gear you could probably go as low as a 3.42 and with the lower 5th gear as high as a 3.23 and be in a comfortable rpm and torque range.


BMC
Brian Mc Cullough
Forest Lake, Minnesota, USA
(380 posts)

Registered:
10/30/2007 02:27AM

Main British Car:
1980 MGB '95 3.4L 'L32' SFI V6, GM V6T5 & 3.42 Limi

authors avatar
Re: Automatic or Standard Transmission in 1961 MGA
Posted by: BMC
Date: April 11, 2008 01:42PM

Sorry I missed this posting from the beginning! Reading through this, I was thinking this may or may not even be a T5 and then you guys go to it...

So here are a few other ideas:
That unit is LARGE and may be possible to switch with an auto since the case will not take any more space on the upper end, but the oil pan could take more room. The T5 will certainly fit in that space with probably only a bellhousing, clutch, HTOB and mount position change.... Oh, and a shifter in a better position!

The top gear in teh V8 T5 is going to be higher than the S10 top gear. Since your going with the V8 T5, move your car to a limited slip with about a 3.4 for Great acceleration with the type of BHP/Tq and power curve that this engine should produce. I have not run the calculations but that should be about right. Camaros with 300+ BHP are looking at 3.42 and 3.73 gears for drag racing but they say that the 3.73 even with the Camaro rims and rubber revs pretty high for daily driving. You could move to the 3.23 ratio (pending this is a GM 7.5" axle?) but since your 5th is already most likely going to be taller, the 3.2 would not be enough of a change.

If this is a Ford 8" or something else, you can find gear ratios similar to the ones mentioned above.

-BMC.


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