gearbox

stevie_a · Postby **stevie_a** » 23 Feb 2010 19:06

Unforchantly it is not a strait in fix

But on the up side a good point for a 5 speed upgrade

as far as i know you need a different back Axel and drive shaft

but the more informed ones among us will be here soon to confirm this for you 

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If it's not broke don't fix it.

busheytrader · Postby **busheytrader** » 23 Feb 2010 21:10

Welcome,

Stevie's right. Unfortunately for your predicament, the 4 speed cars use a different propshaft and rear axle to the 5 speed cars. That also means a different rear brake set up as well.

If the convertible's whole transmission is good you could replace it all in one hit from the gearbox backwards. It's not a small job but replacing the gearbox is probably the hardest part of it.

Adam

TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes all round, Anti- Dive, Strut-Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 5 Spokes and Cruise Lights, S/S Heater Pipes, Replacement Fuel Tank. No Door Stickers. Mine since July 1986, V8 from 1991

Workshop Help · Postby **Workshop Help** » 24 Feb 2010 02:19

I recommend you install a freshly overhauled LT77 5-speed and have the driveshaft stretched to fit from a competent driveshaft service.
By doing so, you will have the best of both worlds, an excellent gearbox and the proper gear ratio in the differential, 3.63:1.

Trust me on this one, this is the setup we use and it is very good. The four speed rear brakes are just fine since they provide far less of the braking power than the front discs do. The five speed rear brakes, tho slightly larger, effect is nullified by the increase in weight from the heavier differential and axles.

By doing this you will avoid much work and expense as well as a redo on the parking brake setup.

Mildred Hargis

nervousnewowner · Postby **nervousnewowner** » 24 Feb 2010 18:48

thats cheating mildred...[:D]

the project at birth, watch it evolve...I hope...

FI Spyder · Postby **FI Spyder** » 25 Feb 2010 19:03

That's a good solution Mildred as the US version has less horsepower and if you don't drive like a madman the Triumph diff will last for a while. The real answer is 3.45 diff and a set of UK 9.25 to 1 pistons to make up the HP needed to compensate. Low RPM, good gas mileage, the best of both worlds. I have the pistons but waiting to come across the diff.

TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra

Beans · Postby **Beans** » 25 Feb 2010 19:21

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Mildred

... LT77 5-speed and have the driveshaft stretched to fit from a competent driveshaft service ... <hr height="1" noshade id="quote"></blockquote id="quote">
Not such a bad idea, only things is that I always thought tne flanges were different?
But even so that shouldn't be much of a problem for a competent drive shaft service.

<center>

1980 TR7 DHC (my first car, currently being restored)
1981 TR7 FHC Sprint (better known as 't Kreng)
[url="http://www.tr7beans.blogspot.com/"]My Weblog[/url]</center>

Workshop Help · Postby **Workshop Help** » 25 Feb 2010 21:02

Yes, my Canadian friend, that 3:45/1 differential is the rare bear. That is why the four speed cars can be updated at a far more reasonable cost with an altered driveshaft.

As for the flange difference, the LT77 rear flange is the same as the four speed flange on the driveshaft. Thus, using a streteched four speed driveshaft or a newly made driveshaft with the four speed flanges on both ends becomes a bolt on proposition without the time, aches, and expense of a five speed rear axle setup.

Oh, and the 9.25:1 pistons would be a nice addition provided they can digest American 87 octane mystery fuel.

Mildred Hargis

FI Spyder · Postby **FI Spyder** » 26 Feb 2010 04:26

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Mildred

Oh, and the 9.25:1 pistons would be a nice addition provided they can digest American 87 octane mystery fuel.
<hr height="1" noshade id="quote"></blockquote id="quote">

If they don't you punch the other button and put in 89 and if that doesn't work you punch the 91 button. If that doesn't work you drive over to the Chevron station and use their 94. For those outside N/A, don't forget you add 4 to 5 octane points to get the equivalent in Europe readings.

(Ron + Mon)/2 (N/A's 91 Octane) = Ron + 5 (Europe's 96 Octane).

While I use 89 in my FI Integra (9 to 1 pistons) I use 87 in my Toyota carbed (also 9 to 1 pistons) and they work fine at sea level. Once a year when I go over the mountains that have a long steep incline that requires full throttle or high speed to make it I put in 94 (half tank) for that part of the journey.

TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra

Underdog · Postby **Underdog** » 26 Feb 2010 15:10

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by FI Spyder

That's a good solution Mildred as the US version has less horsepower and if you don't drive like a madman the Triumph diff will last for a while. The real answer is 3.45 diff and a set of UK 9.25 to 1 pistons to make up the HP needed to compensate. Low RPM, good gas mileage, the best of both worlds. I have the pistons but waiting to come across the diff.

<hr height="1" noshade id="quote"></blockquote id="quote">

I think Team Triumph in Ohio has one but the shipping would kill you.

Jim Underwood
72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

Rich in Vancouver · Postby **Rich in Vancouver** » 27 Feb 2010 04:32

I did the 5-speed swap on my 1975 FHC last summer and it was quite a project to do it correctly. Not only do you need to replace the drivetrain from the engine backplate back but you also need to replace some other bits such as the handbrake cable and the gearshift gaiter and the console pad. The 5-speed even uses a different front subframe. On a car with a stock exhaust manifold you may be OK with the 4-speed subframe. I have headers and ran into interference problems but was able to correct them by shimming the L/H engine mount to increase clearance. If you are having a drive shaft made up, have them use serviceable u-joints rather than the stock CV joints.
I am very happy with the difference in performance and feel with the 5-speed. It feels like a much more modern car. I also have a higher compression engine, headers and performance exhaust, SU carbs and K&N's which combine for a healthy increase in performance.
Unfortunately it's still not quick by modern standards so you have to be careful who you take on in the Rush Hour Grand Prix!

1975 TR7 ACL764U

FI Spyder · Postby **FI Spyder** » 27 Feb 2010 17:17

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Rich in Vancouver

also have a higher compression engine, headers and performance exhaust, SU carbs and K&N's which combine for a healthy increase in performance.
Unfortunately it's still not quick by modern standards so you have to be careful who you take on in the Rush Hour Grand Prix!
<hr height="1" noshade id="quote"></blockquote id="quote">

So all you need now is a hotter road cam and a 3.45 rear end to get rid of that bull low 1st gear. If that isn't enough you can get a 16 valve sprint head conversion (means new intake and headers) for only a few bucks more.[:)]

TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra

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