Engine and Transmission Tech

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

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Dennis Costello
Central Iowa
(134 posts)

12/29/2007 02:53PM

Main British Car:
'73 TR 6 '97 Explorer 5.0

Re: Changing 5th gear ratios on Ford t5
Posted by: IaTR6
Date: October 11, 2018 12:36PM

Tim, If you are at 3500 rpm, and using .63 overdrive, you should read 2205 rpm in 5th. At 4000 in 4th, a .63 5th would give 2520 rpm.
A 3500 to 2500 change is .71, and 4000 to 3000 is .75. Is it possible you have a .73 now, since that would fall within the error of the tach reading?
When I look at my listing of T5's, the .63 5th ratio seems fairly rare. It would mean taking the tail housing off, but for a 2.95 first gear, the overdrive gears should be 25/51T. I assume the aluminum tag with the 1352-11-___ is missing? Is there a partial VIN on the right side of the case on the mounting flange? (outside
surface, not on the bell housing face)
If so, it may be possible to identify the transmission. Case casting numbers are less reliable, but may help also.

Tim Body
St Thomas Ontario
(198 posts)

01/27/2013 06:47PM

Main British Car:
1954 Triumph TR2 stock 2 litre

Re: Changing 5th gear ratios on Ford t5
Posted by: tbo
Date: October 17, 2018 09:44AM

Finally saw how to access the Speed /RPM calculator and got some interesting info.In 4th at 3000 rpm /60mph with the .63 5th gear the revs drop to 1849 a difference of 1085 rpm. With the.73 5th gear the rpm drops to 2142 a difference of 792. With a .80 5th gear the rpm drops to 2318 a difference of 606 rpm . Available Horsepower between 2000 and 4000 is(don't laugh) 85 to 90 . So can I switch to the .73 gears and not have to find a WC trans which will accept the .80 gear set or just plat it safe and go there any way. Of course I have to find a WC trans in good shape with the 295 .63 configuration and then the .80 gear kit . All of that is fraught with problems too.I need a gambler from Vegas to tell me the odds.!! Thanks for the graph Carl
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