transmission questions

[Russ]

I have a nice 66 coupe with 200cid and a C4 and 2.80 rear. I want to convert it over to a manual transmission. I have a couple questions and would very much like to have your opinions. I also have a clutch pedal assy., clutch linkage etc. plus a 2.77 trans and matching 6 cyl. bellhousing. Here are my questions:
1. The trans. has a 2.66 ratio first gear. Do you think that will be too high a first gear for the 2.80 rear[ fairly stock engine ]?
2. If I am going to all the effort to change to manual I was also thinking I might put in something better than the non-synchro 3 speed, perhaps a 4 or 5 speed. What would you recommend from your experience and what bellhousing, flywheel, clutch and other changes would I have to make?
It's a long question but I would really appreciate your experiences as I make up my mind what I want to do.

 

[xctasy]

Don't go 3-speed manual with 2.8:1 !

Here are two reasons why!

1. A manual doesn't have the features an auto has. Autos have a 'stall ratio' equal to a 2.0 to 2. 7:1 ratio first gear, in addition to the given first gear ratio of 2.4:1. They have a 'hydraulically slipping clutch' which won't burn out. Torque multiplication is just fine with autos, so Detriot never needed to go 4 or 5-speed autos untill yeara after the first autos were made.

2. Overall first governs take-off. Take 1st gear, multiply by the diff. For a manual, Under 10:1 is bad, even though plenty of early I6 Fords were running steeper than 9.5:1 (The lower the number, the steeper the gearing).The reason was they were light, and woudln't be expected to tow trailers! Unlike F150/250 I6's, which regularly go shallower than 16:1 on some 4-speed combos.

Using 2.66*2.80, the overall first gear would be 7.448:1, way, way too high. Ideally with a 3-speed, you should aim for no taller than 8.5:1, which means a 3.2:1 diff ratio.

All T5 4-cylinder boxes resulting in a 1 st gear ratio which is too loo. Ford would never release a six cylinder compact sedan with a 12.8:1 first gear, but plenty of guys here use 3.97:1 ist gears with there stock 3.2:1 diff. 12.7:1 first overall, a stump puller of the highest order!

My first Vauxhall got a 4.11:1 diff, 2.85:1 first gear on the 3-on the tree gearbox, with only 77.9 gross horsepower. Overall first 11.7:1.

Then it got a 4-speed box with a 3.36:1 first, and a crown wheel and pinion change to 3.45:1. Overall, 11.6:1. No problem towing even with a gutlless 138 cube in-line six which wouldn't kick out 105 lb-ft in a 2650 pound sedan.

In practice, the diff you have is just perfect for only the T5 non-world-class box from an 81 onwards Fox 2.3 engine. Overall first is 11.1:1. 4th gear is able to do 2400 rpm at 60 mph, and 1900 rpm in overdriven 5th.

It will do wonders for your fuel economy, and its a direct bolt-in with the mods Al organised. Check with some of the others on this forum. There are specific details which vary from car to car, year to year. Specifics are important, but I'd strongly suggest keeping the diff you have. The shaft splines on the output shaft, which were sometimes the same as the C4, so you may be able to use the stock drive shaft.

Guys with 3.2:1 report that T5's are just fine, and have a more usable set of 2nd, 3rd, 4th and 5 th ratios which are not too tall for daily use.

Get feed back from them.

This is why Al decided the best option is to identify the differences, and custom make specilised alloy plates to mount newer T5's on older bell housings. He has dealt with most of the permutations people come up with.

NB// There is the option, at considerably more expense, with more complication, of running a SBF adaptor plate at the engine, which converts the block to a six bolt small block Ford style from the existing 4 bolt pattern. You could then use a 5.0 T5 trans with close ratios for the first 4 gears, and a 38% over drive (0.72:1) on 5 th. You cut up a 200 crank, mill it down plane to about 5/8 ths thick, mount a flange adaptor to the existing crank, then get a plain blank steel flywheel from a race auto shop. It then gets redrilled to the 2.75", 6 bolt pattern. This allows you to use the V8 starter, backing plate, gearbox.Often theres just enough room to accomodate the extra 5/8 ths of an inch the adaptor takes up without cutting the drive shaft. Aussies have been doing this for years on Holdens V8's to mount the THM autos. There's a bit involved here. A set of 3.55:1 gears for the 7.25" diff could then be used to give a 10.4:1 overall first ratio with a 2.97 ratio Ist gear.

 

[LaGrasta]

Russ, where are you at?

 

[xctasy]

I just realised I must have got everyone screwed up regards what the dickens I was talking about when I said

In practice, the diff you have is just perfect for only the T5 non-world-class box from an 81 onwards Fox 2.3 engine. Overall first is 11.1:1. 4th gear is able to do 2400 rpm at 60 mph, and 1900 rpm in overdriven 5th.

WTF is a Fox 2.3 engine? Huh?


Sorry Russ, we car nuts talk in code all the time!

Fox is the generic chassis style Ford made

all 1978-1984 Fairmonts/Zepyhrs,(2.3 engines sometimes came with T5 stick-shifts after 1981)
1979- date Mustangs,(2.3 engines common with T5 stick-shifts)
1980- 1985 Capris, (2.3 engines common with T5 stick-shifts)
1980- the last version Thunderbirds (2.3 Turbo coupes had T5 options)
1980 Lincoln Continetal intermediates (no 2.3 engine, no stick shifts)
1982 Lincoln LSC intermediates (no 2.3 engine, no stick shifts)
1980 Granada on wards (no 2.3 engine, no stick shifts)
1983 Ford LTD compact on wards (no 2.3 engine, no stick shifts)

After 1981, the 2.3 liter OHC engines on some Fox chassis cars so equiped had an optional T5 four cylinder stickshift option.

The best options are 1983 on wards Mustangs with the 2.3 OHC Lima engines.

For the first couple of years, early versions had a funny gearshift pattern which makes getting into 5 th as hard as finding reverse!

Hope this helps!

Regards

xecute