[xk] Re: Close Ratio Gearboxes

Mark:

A 140/150/Mk1/Mk2 close-ratio gearbox has a “CR” suffix to the gearbox
number. There is no change in 4th gear speed as it is direct drive. The
closer ratios for 1st through 3rd are nice, but it really helps to have
the numerically higher overdrive rear axle gears as the CR 1st is
somewhat difficult to live with if one has the non-overdrive axle gears.

Dave Q.
XK150S with CR OD gearbox JLS40444CR> From Mark Stephenson:

Since my 120 has a 140 engine, there is no telling if the gearbox is original. I’m interested in determining if I have a CR box or not. I was under the car the other day and couldn’t find any indication of the gearbox number. I guess it’s on top, so I’ll have to go in through the tunnel. Unfortunately I duct taped everything to cut down on the heat.<
So, my question is, if one has the standard rear end in an XK120, what would be the speeds in mph for 1st through 4th at say 2000 rpm, for the CR box and the standard box? I should be able to tell from that, correct?<

Dave
The 140 OTS I am about to finish sports a CR box. You mention " difficult to
live with"! As it has only been driven once around the block, which hardly
constitutes a fair test, what might I expect re: your comment, and is there
something I have to watch out for?
Best regards…but I have to ask, is it above freezing yet where you live?
Klaus

Klaus,
When I did my XK-140 OTS restoration last year I changed from a standard
ratio to a CR gearbox. The car has overdrive with the 4.09 rear end. I
like the CR box considerably better with the 4.09 rear end. I
particularly notice that the first gear is much easier to use now -
previously it was a real “stump puller”. This has probably a lot to do
with the 4.09 rear end being optimized for fourth gear and the first
gear becoming non optimum.

I’m about to start another overdrive -140 project and would very much
lake to find another CR box or gear cluster.

Regards,

Mike

Cnie104131@cs.com wrote:>

Dave
The 140 OTS I am about to finish sports a CR box. You mention " difficult to
live with"! As it has only been driven once around the block, which hardly
constitutes a fair test, what might I expect re: your comment, and is there
something I have to watch out for?
Best regards…but I have to ask, is it above freezing yet where you live?
Klaus

Klaus:

First the weather. Yes and no. We had a nice March with temps hovering
just above freezing. But, so far, April has been colder!!! Finally,
today we are back on the plus side of freezing (in degrees C) with a +5C
(41F) high. The forecast for the remainder of the week is ‘normal’,
meaning about +10 (50F) for a high. Let’s hope that winter is REALLY
over now.

Now the gearbox. Non-synchro first gearboxes are a pain in almost any
car. My experiences are abundant (MGA/B, TR3, Mini, Austin-Healey,
Morgan/Jaguar Moss box). Most (all non-CR??) have low 2nd gears to
partly make up for this crash-gear, so that accelerating from a
near-standstill can be done in second without much, if any, trouble. The
CR gear ratios make this more difficult as the 2nd gear ratio is higher,
often significantly. A prime example is my MGA Twin-Cam. It has a CR
gearbox but originally had a non-CR box and 4.3 rear gears. There wasn’t
enough grunt to really make the CR 2nd gear useful at low speeds. It now
has the optional 4.55 rear gears which make quite a difference. The
XK140/150 experience is similar, but the choice is/was more varied with
2 sets of gearbox ratios (standard and CR) and 2 standard rear axle
ratios (non-OD and OD, not including the other optional ratios). My
preference would be for a CR box with the OD rear gears (with or without
OD, although OD is extremely nice, IMHO).

Dave Q.
Neuhorst, SK> From Klaus:

Dave; The 140 OTS I am about to finish sports a CR box. You mention " difficult to live with"! As it has only been driven once around the block, which hardly constitutes a fair test, what might I expect re: your comment, and is there something I have to watch out for?<
Best regards…but I have to ask, is it above freezing yet where you live?<

Dave
Thanks for the details which all makes sense. Not yet beeing wise enough in
these matters prompts the next question. Is there a clever way to ascertain
what my OTS has in the rear end from the papers or sundry plates that came
with the car…or do I rise the rear end to count turns.
Needless to say the FHC has not received a lot of atttention the last 12
month, having retired, moved to CT to a new (old) abode with a long Honey Do
list and above all getting the OTS on the road. But, there are more winters
coming… how is your retoration faring?
Best regards

You should find a tag on the diff casing, it is held on by one of the bolts
holding the rear inspection plate. you will probably have to take it off to
read it. It will say something like 45/11
which equals 4.09 : 1

regards

Peter M> -----Original Message-----

From: Cnie104131@cs.com [SMTP:Cnie104131@cs.com]
Sent: 17 April 2000 16:08
To: xk@jag-lovers.org
Subject: Re: [xk] Re: Close Ratio Gearboxes

Dave
Thanks for the details which all makes sense. Not yet beeing wise enough
in
these matters prompts the next question. Is there a clever way to
ascertain
what my OTS has in the rear end from the papers or sundry plates that came

with the car…or do I rise the rear end to count turns.
Needless to say the FHC has not received a lot of atttention the last 12
month, having retired, moved to CT to a new (old) abode with a long Honey
Do
list and above all getting the OTS on the road. But, there are more
winters
coming… how is your retoration faring?
Best regards

Klaus:

The answer is?? Not that I know, but others may. My axle/diff didn’t
have any tell-tale tags or such on it. Like me, I guess that you will
just have to do the old lift and count trick.

My restoration?? Well, I have acquired just about all of the car’s
missing hard parts. I just need overdrive parts, 3.4 150S distributor,
tranny tunnel, and the leather/chrome instrument panel cover to complete
it. Then comes the actual rebuilding fun stage. But at least the end
will be coming closer once I actually get serious with that stage. It
would be nice to be able to actually have it move under its OWN power
(rather than mine). It hasn’t since 1979 or so.

Dave Q.> From Klaus:

Dave; Is there a clever way to ascertain what my OTS has in the rear end from the papers or sundry plates that came with the car…or do I rise the rear end to count turns. how is your retoration faring? Best regards. <

Dave
Thanks for the news. You can get a tranny tunnel from Wray Schelin if you
cannot find a good used one. He makes good parts.
Pardon my ignorance, but how do you do the snip-snip trick to shorten a
reference to a reply.
Thanks
Klaus

Klaus,

Simple, really, but all manual. When you hit the Reply to Sender button and
you have the original e-mail below where you are typing, just highlight a
superfluous section and then type “” in its place. If you want to be
perfect, get the on a line by itself.

“Mark 1” Mark Stephenson
1952 XK120 Roadster #S673129 (w/XK140 engine and C head)
1958 3.4 Litre Saloon / 1984 XJ6 4.2L / 1985 XJ6 VDP / 1986 XJ6 VDP
Jaguar Club of Central Arizona (USA) – www.cableone.net/jcca----- Original Message -----
From: Cnie104131@cs.com
To: xk@jag-lovers.org
Sent: Thursday, April 20, 2000 8:24 PM
Subject: Re: [xk] Re: Close Ratio Gearboxes

Dave
Thanks for the news. You can get a tranny tunnel from Wray Schelin if you
cannot find a good used one. He makes good parts.
Pardon my ignorance, but how do you do the snip-snip trick to shorten a
reference to a reply.
Thanks
Klaus

I probably should know the answer to this what would be the gearbox number be on an XK120 gearbox with close ratio gears?