Subject: [Tigers] Gears and rpms

From: "Andy Walker" <[email-masked]>
Date: Tue, 6 Aug 2013 22:44:12 -0500

Hey, guys:

I've got a question for some of the more mathematically proficient in the
group.  I'm considering making some changes to my Tiger pertaining to the
rear end gear ratio.  Can anyone tell me how to figure what kind of rpm
difference there would be at, say 70 mph, between a Tiger equipped with a
stock 2.88:1 rear end and one equipped with first a 3:07.1 and then a 3:31.1
rear gear?  Surely there's a formula out there that can figure that.  Can
anyone point me in the right direction?    

The bottom line here is that I need something that will get my car off the
line a bit quicker without completely destroying my highway cruising
capabilities.  I currently am running an Edelbrock F4B and a Holley 465 cfm
carb, a hydraulic version of the old Ford hi-po cam, and 13" LAT 70s with
185/70 tires.  The car currently has a 2:88.1 rear gear and that makes it a
bit sluggish off the line.  I've heard it said that a 3.07:1 gear was about
ideal for a stock Tiger, but with the cam and carburation my car has, would
a 3.31:1 be a better alternative?

Thanks for any advice,

Andy Walker

Edmond, OK

B382001600LRXFE

TAC #740
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From: TtT <[email-masked]>
Date: Wed, 07 Aug 2013 02:26:28 -0500

Andy, if you go to 331 gears, you will have wheel hop with higher rpm line shots when running 13 inch wheels. Assuming the hp is there. My first Tiger (1972)  had 331 gears, 13 inch wheels with 60s and a 289 with a huge can, it ate my. 2nd Tiger alive (I bought it later from my friend)  which had a rebuilt 260, four barell intake and Carb. with 288 gears.I'm now running 288 gears a five speed and 15 inch wheels. I can go through town in 5th gear at 1000 rpm, my speedo has never worked since the
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Andy Walker <[email-masked]> wrote:

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From: TtT <[email-masked]>
Date: Wed, 07 Aug 2013 02:49:53 -0500

sorry ..... since the T5 installation, so I can't speak to gas milage but I have. no wheel hop but better traction would be a plus. I'm also running stock 288s. I think if I had wider tires and whatever is now the best traction inhancer the LIST recommends I would have a great setup.I'm running a 302 with 289 CI heads using 350 Chevy valves, for shame, for shame and a mild can. Duke has me needing a stroker engine.That said, I don't think the five speed will hold up to lots of HP and as mentioned the wide ratio should be considered. Meanwhile I think my setup is great, I just want /need more HP and then I may have to adjust. Good Luck. TtT 
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From: <[email-masked]>
Date: Wed, 7 Aug 2013 9:58:16 -0400

A big "thank you" to all of you who responded to my gearing question!!!  The calculators and spreadsheets that several of you turned me on to are of great assistance.

So, the general concensus I'm getting from you guys appears to be that the close-ratio tranny is more of a culprit in contributing to slower off-the-line response than is the rear end ratio.  Going to the wide-ratio gears does sound like the answer I'm looking for as it yields the best of everything without cutting up the car; quicker response off the line and easier on the clutch while still maintaining the highway rear gear advantages of less noise, less wear and tear on the engine and reasonable gas mileage.  This may be the route that I should take as I'm going to have to have my trans gone through anyway when I replace the clutch in the car this winter.  This would be a great opportunity to make the suggested ratio changes.

Having said that, it appears that most of you who have made this change have done so by just changing the gears in your close-ratio boxes.  So, to Gary and others who have done this, where should I be looking for the parts I would need to make the recommended gear ratio changes?  

Thanks again for the suggestions and assistance,
Andy Walker
Edmond, OK
B382001600LRXFE
TAC #740

---- michael king <[email-masked]> wrote: 
> Andy,
> 
> with 185/70/13's the following will be the RPM/speed:
> 
> 3.07:1
> 60mph: 2669 rpm
> 70mph: 3114 rpm
> 
> 3.31:1
> 60mph: 2878 rpm
> 70mph: 3357 rpm
> 
> For what it's worth. if you are prepared to pull the rear end... dont...
> you are better off switching to the wide ratio trans gears.. you will get a
> shorter first and quicker take off without hurting cruising rpm. I have a
> 3.07 and run 195/60/14 ... the wide ratio gives a better first than i have
> even with shorter gears,, and better highway.
> 
> The 5 speed is the best option.. you could run a slightly shorter rear..
> have brutal acceleration.. and still better than stock highway... then
> again.. traction might be harder to come by off the line...
> 
> i would switch out your first gear ratio before you swap the rear end. just
> my .02
> 
> 
> 
> -- 
> Regards
> 
> Michael King

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From: [email-masked]
Date: Wed, 7 Aug 2013 10:05:14 -0400 (EDT)

Seems to me that a change in rear end gear ratios would also be a ratio.  
For example, going from 2.88 to 3.07 would give a ratio of 1.066. Taking this 
 times the RPM at a speed using 2.88 gears and multiplying by 1.066 gives 
the RPM  with the new gears at the given speed.
 
My Tiger runs 2400 RPM at 60 MPH with 2.88 gears. With 3.07 gears the RPM  
would be approximately 2558 RPM. This assumes everything else stays the  
same.
 
Fred Baum

In a message dated 8/7/2013 9:58:23 A.M. Eastern Daylight Time,  
[email-masked] writes:

A big  "thank you" to all of you who responded to my gearing question!!!  
The  calculators and spreadsheets that several of you turned me on to are of 
great  assistance.

So, the general concensus I'm getting from you guys appears  to be that the 
close-ratio tranny is more of a culprit in contributing to  slower off
-the-line response than is the rear end ratio.  Going to the  wide-ratio gears 
does sound like the answer I'm looking for as it yields the  best of 
everything without cutting up the car; quicker response off the line  and easier on 
the clutch while still maintaining the highway rear gear  advantages of less 
noise, less wear and tear on the engine and reasonable gas  mileage.  This 
may be the route that I should take as I'm going to have  to have my trans 
gone through anyway when I replace the clutch in the car this  winter.  This 
would be a great opportunity to make the suggested ratio  changes.

Having said that, it appears that most of you who have made  this change 
have done so by just changing the gears in your close-ratio  boxes.  So, to 
Gary and others who have done this, where should I be  looking for the parts I 
would need to make the recommended gear ratio  changes?  

[email-masked]

---

From: [email-masked]
Date: Wed, 7 Aug 2013 16:19:35 -0400 (EDT)

LOL

In a message dated 8/7/2013 4:15:29 P.M. Eastern Daylight Time,  
[email-masked] writes:

I have  never liked the close ratio tranny.  It made the car a chore to  
drive
in my opinion.  I went to a wide ratio and it immediately became  more
pleasant.  Coming off the line no longer required me to feather  the
throttle.  It was the single best change I did.

Regarding  your other questions I think many of us would answer as follows:

Are we  street racing from light to light?  Yes
Drag racing? Every chance I  get.
Have more money for fuel or what?  Just on pay day
Some kid in  a KIA get after you (us)?  Little  pricks
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