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

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rficalora
Rob Ficalora
Cypress, TX
(2377 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Gear ratio calculator, rear gears, and transmission ratios
Posted by: rficalora
Date: November 02, 2017 08:40PM

Can someone point me to the Microsoft Excel gear ratio calculator that was posted several years back? It enabled you to input transmission gears, rear end gear, tire size, etc and calculated speed at RPM for each gear.

I want a better 1st gear ratio - or possibly different 1st and rear gears.



Edited 1 time(s). Last edit at 11/15/2017 10:20AM by rficalora.


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 02, 2017 08:41PM

Rob, What do you have for first and rear gears?


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Gear ratio calculator
Posted by: MGBV8
Date: November 02, 2017 09:34PM

Gonna cost you big bucks either way since you can't just change out 1st gear.


MGBV8
Carl Floyd
Kingsport, TN
(3232 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Gear ratio calculator
Posted by: MGBV8
Date: November 02, 2017 09:44PM

Quote:
Borg Warner T5 five speed from a 1994-95 (SN95) Ford Mustang. (Input shaft and bellhousing are 1" longer than typical 5.0L Mustangs. Gear ratios: 3.53:1, 1.93:1, 1.33:1, 1.00:1, 0.68:1, and 3.15:1 reverse. 1-1/16" 10-spline input shaft. 0.668" input shaft pilot diameter. 28-spline output shaft. 8-tooth speedometer drive gear. ATF fluid.) King Cobra clutch. 1994 Toyota 4Runner slave cylinder.

Rear End: 1996 Nissan Skyline viscous limited slip differential (same R200S case as Nissan 240SX). 3.54:1 gears. Uprated halfshafts from "The Driveshaft Shop" in Salisbury, North Carolina.

Yeah, I wouldn't be happy with that 1st gear, either. I would like the 3:54 rear gears with my 2.95 1st gear. You could go with a 3.08 since you have that 302 torque.

Dan Masters' gear ratio calculator (in Excel) [www.britishv8.org]


v8mgb
Jim Miller

(33 posts)

Registered:
01/01/2008 11:38AM

Main British Car:
78 MGB Buick 215

authors avatar
Re: Gear ratio calculator
Posted by: v8mgb
Date: November 02, 2017 09:46PM

Rob: Google Search found this

[www.glenn-ring.com]

[www.tremec.com]



Edited 1 time(s). Last edit at 11/02/2017 09:48PM by v8mgb.


rficalora
Rob Ficalora
Cypress, TX
(2377 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator
Posted by: rficalora
Date: November 02, 2017 10:48PM

Thanks. Note there's a typo in the HIWD, current 1st is 3.35.

Tires are 225/45/15 so about 23" diameter.

Carl - yeah, pretty much requires changing clusrer. There's a guy who'll build me what I'd need for about $1200 (with no core charge) I think I could resell my current trans for $600-750 so makes it fairly doable.



Edited 2 time(s). Last edit at 11/03/2017 01:00AM by rficalora.


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 02:40AM

Rob, Ford Racing T5Z has the 2.95 first. Or like Carl mentioned the 3.08 rear gear. The V8 can pull a taller gear fine. The V6 guys like around 12 combined first and rear. Higher power V8 do better in the 10's. Unfortunately you would have to switch to the 8.8 for the 3.08. I think the Nissan 200R 3.54 is the highest ratio they have. Also the 2.95 only comes in the shorter pre 94 input length. I did find this aftermarket 94 and newer input shaft, you would use your bearing retainer:

[www.ebay.com]



Edited 4 time(s). Last edit at 11/03/2017 03:18AM by mgb260.



BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(5343 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Gear ratio calculator
Posted by: BlownMGB-V8
Date: November 03, 2017 11:13AM

Mine comes out to 11.5 with a 25.7" tire (3.54 x 3.27). Equivalent to 10.7 with a 24" tire or 10.3 with a 23" tire. Still a kinda short 1st gear but at least usable and good for launches. Much better that the T5 that's in the car right now which works out to about 12.7 with a 23" tire or 13.3 with a 24" tire. That one is still usable but almost pointless. Tire diameter increases are roughly equivalent to steps in axle ratio, so keep that in mind too.

I'm going to need to swap out that tranny soon. Maybe this weekend would be good, I think I have everything now.

Jim


rficalora
Rob Ficalora
Cypress, TX
(2377 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator
Posted by: rficalora
Date: November 03, 2017 01:49PM

I'm seeing on the internet that Titans, Armada's, & XTerra's had a 2.95 rear so I did the following compares. What would you do based on these?
Transmission & Rear Gear swap graphs 1.jpg
Transmission & Rear Gear swap graphs 2.jpg


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 02:53PM

Rob, Those rears are much larger than your R200. I think about a 10" ring gear compared to your 8". I think the 2.95 first in the transmission would be your best bet. 2.95 x 3.54 = 10.44. Your lower profile tires, like Jim B mentioned above, also lower the rear ratio. I googled the R200 gear ratios and the ones you have are the highest available for that rear.



Edited 1 time(s). Last edit at 11/03/2017 03:06PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 02:55PM

Tire size to gear ratio calculator, Shows your effective rear ratio is now 3.68 :

[tiresize.com]



Edited 1 time(s). Last edit at 11/03/2017 02:57PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 04:10PM

Rob, 91-96 and 99-08 Infiniti G35 used 3.36 gears in the R200 with the automatic transmission. The older R200 longnose in the 280ZX turbo and 2+2 also used that ratio but has smaller holes in the ring gear and longer pinion so I don't think that would be viable. You may be able to find the Infinity G35 in a pick and pull. Gear tooth count is 37-11.



Edited 3 time(s). Last edit at 11/03/2017 04:19PM by mgb260.


rficalora
Rob Ficalora
Cypress, TX
(2377 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator
Posted by: rficalora
Date: November 03, 2017 04:20PM

Bummer on the 2.95 rear gear. I googled R200 ratios & found it there; must not have looked close enough at the page :(.

So, sounds like the 2.95 1st gear transmission & find a 91-96 Infinity G35 will be my best answer.


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 04:45PM

Rob, The Newer 99-08 G35 have that ratio too. That combo would be perfect for your car. Lots of the newer ones, some with Limited Slip on Ebay.

[www.ebay.com]



Edited 1 time(s). Last edit at 11/03/2017 04:46PM by mgb260.


IaTR6
Dennis Costello
Central Iowa
(114 posts)

Registered:
12/29/2007 02:53PM

Main British Car:
'73 TR 6

Re: Gear ratio calculator
Posted by: IaTR6
Date: November 03, 2017 05:30PM

I seem to be thinking along the same lines. I have the R200 w/3.54 and a T5 with 3.35 1st. and I would like more range in 1st gear.
In traffic, I am shifting too soon. I suppose it would be O.K. for a heavy vehicle, and it keeps me from stalling it, but the 302 torque
would seem to allow something taller. Now I have 3.35X3.45=11.86, and a change to 2.95 would be 2.95X3.54=10.44, which would be better.
Changing the input, cluster and the 1-2-3 gears on the mainsheet gets pricey, and leaves you with a .59 ratio 5th, which is very tall.
I have not found a combination of 5th gears that suit me, but the T5Z has a .63 5th, which would do. Of course, they are $1750!
I'll watch here for a while and see what the wiser folks do.
Dennis



mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 05:48PM

If you don't have a super powerful (over 300HP) V8 you may get by with the NWC 83-84 Mustang T5. It had the 2.95 first and some had the .72 OD. Probably hard to find and I would still do a rebuild, use Synchromesh fluid and a aftermarket shifter with stops.


IaTR6
Dennis Costello
Central Iowa
(114 posts)

Registered:
12/29/2007 02:53PM

Main British Car:
'73 TR 6

Re: Gear ratio calculator
Posted by: IaTR6
Date: November 03, 2017 05:51PM

Rob, Look at this link, it refers to a Pathfinder with a high ratio in the 3. something range.
More research to see if the info is valid!
[zilvia.net]
Dennis


mgb260
Jim Nichols
Sequim,WA
(1804 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator
Posted by: mgb260
Date: November 03, 2017 06:09PM

Dennis, Good find! 3.113 ratio. That would be 10.43 combined with the 3.35 first you already have. Rob would be lower with his 23" diameter tires at 10.82.

[www.ebay.com]



Edited 2 time(s). Last edit at 11/03/2017 06:14PM by mgb260.


IaTR6
Dennis Costello
Central Iowa
(114 posts)

Registered:
12/29/2007 02:53PM

Main British Car:
'73 TR 6

Re: Gear ratio calculator
Posted by: IaTR6
Date: November 03, 2017 06:17PM

Oh, something else that popped into my head was the notion that the point of greatest torque multiplication has the greatest stress.
I may be wrong on that, and someone can jump in here, but a numerically high rear ratio would move the stress to the transmission,
which in the case of the T5 is around 300 ft lb. in the better models. Higher capacity can be had for a price of course.
So, I'm leaning toward a 2.95 1st gear and leaving my 3.54 ratio R200 as is. That's still 10.4 overall.
Dennis


rficalora
Rob Ficalora
Cypress, TX
(2377 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator
Posted by: rficalora
Date: November 09, 2017 09:40PM

I've been researching the Pathfinder 3.13 - seems like it only came in an open differential. No LSD. Anyone familiar with Phantom or Traction Concepts? They advertise these things that can be installed to give it LSD... [www.ebay.com]
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