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Old 01-01-2002, 03:08   #1 (permalink)
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Ratio change to 3.73

I've got an EB 5.0 auto that I recently did some head work to and fitted a set of YT 1.72 roller rockers to raise the lift of the stock cam. I am now looking at changing the rear end ratios.

I have read on US Ford sites that 3.73 is highly recommended for Stangs with autos. As their gearbox ratios are similar to mine this is what I would like to fit.

After ringing about 10 diff places in Melbourne only one stated a new 3.73 ratio can be fitted to the B/W 78 series diff in the EBs, the others were all stating that I'll have to fit a used 3.70 out of a Skyline. I prefer to go with a new gear set and also the place that said it can be done is pretty good doing work on my LSD in the past.

I read on another thread posted a couple of weeks ago that 'Blown EF 6' has a 3.73 fitted. What I would like to know is, is the EF housing the same as the EB? Can a 3.73 be fitted to my diff? Also, how much improvement is there with the shorter gearing?

Thanks,
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Old 01-01-2002, 03:39   #2 (permalink)
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An EL in Steet Machine had that gearing & said it was made for TVRs in limited numbers if that helps
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Old 01-01-2002, 04:04   #3 (permalink)
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Just out of interest how does the car go now with the 1.72 rockers??? I've got a stocko EF 5L and was thinking exhaust/rockers/unichip would be my plan of attack.

As for the diff ratio i'm just lookin around for a 2nd hand XR6/8 LSD. These are 3.45:1 and i couldn't imagine a 3.73 being a hell of alot quicker. Remember you will lose out in the top end by shortening the gearing - GTS300's have 3.9:1 gearing but they also have 300kW and 6 gear ratios..
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Old 01-01-2002, 05:20   #4 (permalink)
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PigDog, I noticed good improvements by fitting 1.72 ratio roller rockers. The car feels torquier and pulls a lot better than before. It revs out to 5,800 easily, however, this may have more to do with the heads. Initially, I was after a cam change but after reading a lot of stuff from the States that the stock cam has a pretty decent grind it made more sense to me to do this as I only wanted something mild.

I couldn't tell you how much power and torque I've picked up because I haven't done a power run yet. I have a book from the States where they dynoed a stock 5.0 with 1.7 rockers and it picked up about 7kw and 20 nm.

I have extractors and a genie 2.5" single system on it but I am a bit reluctant to fit a chip to it because the car is running as smoothly as before. I feel that changing the ratio is better value for money as it will allow it to pick up good acceleration. I realise that I'll lose top speed, but theoritcally it should still see 190 - 200, but then again where can you see that type of speed.
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Old 01-01-2002, 14:20   #5 (permalink)
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Thanks for that information mate.. looks like the rockers will be a fairly good value mod. What kind of headwork was done? I've heard the exhaust ports are very restrictive on the 165kW motors so there was probably a good gain to be had there..
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Old 01-01-2002, 19:30   #6 (permalink)
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3.73 and 3.9 ratios do fit but they require a bit of hard work and custom made shims. I changed mine to 3.45, wasn't happy and then went 3.9 ratio. 3.45 aren't great with an auto. With the 3.9's you get much quicker response but with an increase in fuel consumption. Mine cost $1050 all up with the correction box for the spedo.
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Old 01-02-2002, 01:39   #7 (permalink)
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PigDog. There's a good article on porting stock heads at http://www.fordmuscle.com/archives/2...g/index.shtml. This will show you how restricted the stock heads are.

Basically, I had Eugene of Flowcraft port and shave the heads, do a four angle valve job, fit 351 Windsor intake and exhaust valves, as well as Cleveland springs.

Thanks EDXR8. Do you know what car the 3.73 ratio comes out of. I've been told that 3.45s don't make that much difference on an auto, particularly since I'm at 3.27 already. I was also told that 3.9s are available as a new gear set, however, I think this could be a bit too much for me particularly since it spends most of its time on the highway. I'm prepared for the drop in fuel consumption but how much did you end up losing overall.

Regarding the speedo I'm actually going to change the speedo gear to a 23 tooth and get it trimmed one more tooth to make it spot on. All up I've been quoted $1,100.
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Old 01-02-2002, 01:44   #8 (permalink)
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Pig Dog. Sorry, I stuffed it up. Click on to www.fordmuscle.com. Go through archives and its under 'Port your own heads.'
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Old 01-02-2002, 04:11   #9 (permalink)
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Thanks mate that's an excellent website!! The best article i found was this one

http://www.fordmuscle.com/phpBB/view...=209&forum=4&0

Not real sure if i wanna go as far as you have for the time being, but i definently plan on doing the rockers in the near future. Might hold off on headwork till i've got the cash for a nice stroker bottom end to go with em :s5
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Old 01-02-2002, 04:16   #10 (permalink)
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Quote:
Originally posted by EDXR8
3.73 and 3.9 ratios do fit but they require a bit of hard work and custom made shims. I changed mine to 3.45, wasn't happy and then went 3.9 ratio. 3.45 aren't great with an auto. With the 3.9's you get much quicker response but with an increase in fuel consumption. Mine cost $1050 all up with the correction box for the spedo.
Mate you've fitted a 3.9 diff, what was she turning at 100km/h just interested to know.

For my driving sytle with alot of relatively high speed cruising ie 120-140km/h i'm reluctant to even move to 3.45.
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