Gear Ratio Comparasions

jeffremj · Postby **jeffremj** » 12 Aug 2013 15:37

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

Okay, with the first few numbers in, let's start some analysis.

Nick with his supposedly 1980 LT77 and a 3.45 differential is at 2500rpm@60mph.

Russ with his 1980 LT77 and a 3.90 differential is at 3000rpm@60mph.

Hasbeen checks in with near identical numbers to Russ. We thank you.

That's a 500 rpm difference.<hr height="1" noshade id="quote"></blockquote id="quote">My TR7 booklet mentions 20.8mph/1000 revs in 5th. Therefore Russ should be showing around 63mph @ 3000rpm.

Further to this, I found that my TR7 speedo was over-reading and so I fitted a different speedo cog. It had one more tooth and this slowed the speedo by around 5%. On my TR7V8, with 3.08:1 diff and TR7 gearbox, I managed to get a standard TR7 speedo to give very good figures when using the cog with the lowest teeth that BL made. Figures checked on a rolling road - 71 shown 70 mph true. Tyres were 205/50x15 - this has an affect!

Beans · Postby **Beans** » 12 Aug 2013 17:01

1980 TR7 DHC with correct 5 speed 'box in 5th gear of course, 3.45:1 diff and 185/70-13 tyres @ 2.1 bar cold
(and the speedo proved to be frighteningly accurate as the GPS was reading 120 km/h)

And doing 60 MPH can be dangerous in Germany [:p]

<center>

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

Workshop Help · Postby **Workshop Help** » 12 Aug 2013 18:45

Please, allow me to convert your foreign KPH to the more civilized MPH; 120KPH = 74.5645MPH, per the Google conversion chart.

Will there be a posting of a photo showing the tachometer reading at a pokey slow 60MPH or 96.5606KPH for our comfort & convenience?

Mildred Hargis

Beans · Postby **Beans** » 12 Aug 2013 19:12

60 MPH should be at around 2375 RPM.
Will check as soon as she's ready for the 10CR

<center>

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

Beans · Postby **Beans** » 12 Aug 2013 19:16

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

Please, allow me to convert your foreign KPH to the more civilized MPH ...<hr height="1" noshade id="quote"></blockquote id="quote">
Opions on that vary a lot on the continent [:D]

<center>

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

john 215 · Postby **john 215** » 12 Aug 2013 19:31

Hi,

Mine is 2.84:1 and a late higher 5 gear LT 77, 14 inch wheels equals 2000 rpm ish but not really applicable as you guys are talking 2 litre cars I guess.

Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!

1976 Speke FHC Beauty

1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6,ON THE ROAD NOW KICKING AR5E !!!!

Workshop Help · Postby **Workshop Help** » 12 Aug 2013 20:05

We have a new winner: Beans! With a chugging low 2375 RPM's!

Who's next? I'm thinking a 3.08 differential with a late 1981 LT77 might get it on down to just over idle speed. I've always dreamed of slipping the 3.27/1 automatic cars differential into my rear housing. But, I never could find one.

You folks with TR8's need to get in on this as well in your own category.

Mildred Hargis

FI Spyder · Postby **FI Spyder** » 12 Aug 2013 23:54

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

I would say you have the 3.45:1. You have to jack the car and look at the bottom of the differential. Scribed (not stamped) will be a code. Here is the key:
5 speed 3.9:1 CH
5 speed 1980-81 3.45:1 CL
4 speed 3.63:1 CG
Auto 3.27:1 CT

You may have to scrape off some grime to find the code since it is scribed into the metal.

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

What do you mean by scribed? To me scribed and stsmped mean the same thing with the other type being "cast".

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

FI Spyder · Postby **FI Spyder** » 12 Aug 2013 23:55

I think I need a six speed.[8D]

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

whitenviro · Postby **whitenviro** » 13 Aug 2013 03:11

I don't know what ratio have, so I was hoping this discussion would help me figure it out. With standard 185/13" wheels I noticed on my recent trip that in 5th gear I was at 3000 rpm at 70 mph. I don't recall ever traveling at 60 mph....

[/img]
1980 Pageant Blue DHC with removable hardtop.

Hasbeen · Postby **Hasbeen** » 13 Aug 2013 03:25

Whitenviro that sounds to me like a standard 3.9 giving 62.5 MPH at 3000RPM, with the usually 8/9% fast speedo.

All my 7s bar the current one were reading about 70 MPH at 3000 RPM, while I was actually doing just over 60. Have you ever checked it against a sat nav?

I'm sure this was most advantageous in preventing me getting booked on our mostly 100Km/H, [62.4MPH] speed limit roads.

Hasbeen

Odd · Postby **Odd** » 13 Aug 2013 06:20

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Mildred
Please, allow me to convert your foreign KPH to the more civilized MPH ... <hr height="1" noshade id="quote"></blockquote id="quote"><blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Beans
Opions on that vary a lot on the continent [:D] <hr height="1" noshade id="quote"></blockquote id="quote">Second that!
And not only on this, the largest land mass/continents... [:)]

silverseven · Postby **silverseven** » 13 Aug 2013 09:34

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

I would say you have the 3.45:1. You have to jack the car and look at the bottom of the differential. Scribed (not stamped) will be a code. Here is the key:
5 speed 3.9:1 CH
5 speed 1980-81 3.45:1 CL
4 speed 3.63:1 CG
Auto 3.27:1 CT

You may have to scrape off some grime to find the code since it is scribed into the metal.

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

Scribed as in chalk mark ??

My diff has been Ziebarted and painted , so I doubt this would be visible anymore...... I was hoping for a tag or as Spyder said a casting.

It's raining today , so I might take the wedge into the shop and maybe throw it up on the ramp and inspect the rear a little closer tonight.(who knows??)

Ron.

john 215 · Postby **john 215** » 13 Aug 2013 10:10

Hi,

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> I think I need a six speed.<hr height="1" noshade id="quote"></blockquote id="quote">

How about one of these -

TR7 four speed gearbox, overdrive 3rd and 4th hey presto 6 speed box [:p]

Will be intresting to see what revs at 60 mph are ????

Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!

1976 Speke FHC Beauty

1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6, BUILT NOT BROUGHT !!!!

nick · Postby **nick** » 13 Aug 2013 16:47

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

[quote]Originally posted by nick

I would say you have the 3.45:1. You have to jack the car and look at the bottom of the differential. Scribed (not stamped) will be a code. Here is the key:
5 speed 3.9:1 CH
5 speed 1980-81 3.45:1 CL
4 speed 3.63:1 CG
Auto 3.27:1 CT

You may have to scrape off some grime to find the code since it is scribed into the metal.

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

What do you mean by scribed? To me scribed and stsmped mean the same thing with the other type being "cast".

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

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

By scribed I mean written with a sharp objected as opposed to raised as part of the casting. The former gets covered by dirt and grime while the latter does not.

[img][IMG]http://i615.photobucket.com/albums/tt234/nickmi/TR7%201975/Yellow.jpg[/img]
nick
'79 TR7 DHC
'76 TR7 FHC

Anonymous

Gear Ratio Comparasions

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