Changed 5th gear ratio-Tremec T3650 - Ford Forums

paulhowes · 04-20-2006, 16:46

For those of you that have this box you will know it is a huge distance between 4th and 5th gear and the car dies in the ar*e and on hills gives no performance. I drove 900km to Mal Woods and had him change the ratio of 5th gear and what a difference it made, this car on the Putty road now convincingly overtakes up hill in 5th. I went from 0.62 to
0.74 and it now revs just under 2250 at 100km/h and around 2400 at 120km/h. I never drove (mostly) faster than this anyway but now it gets up and goes when you put your foot down at that speed in 5th. Overdrive can also be used from 70km/h now. It was a good low cost mod.($700)
more than happy but a six speeder would be better. At $7000 I will have to think about that one.

Lowride260 · 04-20-2006, 23:48

Mate you proberly would done better changing the diff ratio pull better in every gear for a similar price.

paulhowes · 04-21-2006, 01:02

Quote:

Originally Posted by Lowride260

Mate you proberly would done better changing the diff ratio pull better in every gear for a similar price.

If you had driven these vehicles for some time you would note that 1st and 2nd gear are somewhat lower than that in the Bf and to change the diff would go nowhere. The BA was given taller 1st and 2nd after lessons learnt off these cars. The right setup is 3.7 rear with taller 1st and 2nd like the Bf in a six speeder. The problem was the huge gap between 4th and 5th, an unrealistic silly gap. My 5th was the same ratio as the BF 6th. Imagine driving a BF with no 5th gear and thats what you faced. No diff changing would close that gap.

Lowride260 · 04-21-2006, 16:28

Quote:

Originally Posted by paulhowes

If you had driven these vehicles for some time you would note that 1st and 2nd gear are somewhat lower than that in the Bf and to change the diff would go nowhere. The BA was given taller 1st and 2nd after lessons learnt off these cars. The right setup is 3.7 rear with taller 1st and 2nd like the Bf in a six speeder. The problem was the huge gap between 4th and 5th, an unrealistic silly gap. My 5th was the same ratio as the BF 6th. Imagine driving a BF with no 5th gear and thats what you faced. No diff changing would close that gap.

Remeber 5th gear in the 5sp is only a overdrive (cruise/ecconmy) not a accelerating gear, in my 6sp the 6th gear is even higher than the 5th in the 5sp awsome for cruising on the hwy.
I only say changing the diff ratio you can improve the down low in every gear and improved ecconmy around town and gain a little torque in 5th at the same time.
And on the BA having taller gears my 6sp has a lower ratio than the 5sp in 1st and 2nd and the BF 6sp auto has even low again (rember there final drive 2.75)

paulhowes · 04-21-2006, 20:06

Quote:

Originally Posted by Lowride260

Remeber 5th gear in the 5sp is only a overdrive (cruise/ecconmy) not a accelerating gear, in my 6sp the 6th gear is even higher than the 5th in the 5sp awsome for cruising on the hwy.
I only say changing the diff ratio you can improve the down low in every gear and improved ecconmy around town and gain a little torque in 5th at the same time.
And on the BA having taller gears my 6sp has a lower ratio than the 5sp in 1st and 2nd and the BF 6sp auto has even low again (rember there final drive 2.75)

Is your 6sp a man or auto. we are not talking autos here its manuals.Remember this is not a T5 it is a T3650 Tremec.Check the specs. in the T3650 the 5th gear is 0.62 which is taller than 6 speed man has for 6th gear (which is 0.63) and their 5th is 0.8. Try driving a 6sp manual on all sorts of roads without using 5th gear having that huge jump from 4th (same ratio as mine) to 6th (lower than my 5th). I bet you cant do it without using fifth gear at least once. First gear in 6sp man is 2.98 compared to a lower
3.37 in the T3650 2nd in the 6sp man is 1.78 compared to a lower 2.0 in the T3650 and diff ratios are same in both manuals. 5th gear is ideally an overdrive but when 4th starts asking to change gears at 90 to 100 k's a more sensible overdrive is 0.74 which still works as an overdrive but doesn't have my foot flat to the floor to maintain 100K's up a steep hill, it will now cruise that hill still with low revs (just not rediculously low) and partial acceleration. I wouldn't have minded the car dying in the ar*e in 5th if it wasn't for the huge gap to drop back and over rev 4th. If I changed the diff 1st and 2nd would be rediculous and 4th would scream over 80K's. a 3.7 diff at 100km/h would only have brought my revs up by 100 revs in 5th (still a little tall) but in 4th would have added 300+ revs Ideally i wanted it to rev at around 2000 at 100km/h and I have achieved this without sacrificing the length of my lower gears. Each to their own this worked for me but wont be for everyone. Cheers.

Gambit · 04-26-2006, 22:16

Quote:

Originally Posted by paulhowes

The BA was given taller 1st and 2nd after lessons learnt off these cars.

I thought they changed the diff ratio from the 250's 3.45 to 3.23 for the manual ba XR/FPV with the 5sp box to make 1st more useable.

paulhowes · 04-27-2006, 03:13

Quote:

Originally Posted by Gambit

I thought they changed the diff ratio from the 250's 3.45 to 3.23 for the manual ba XR/FPV with the 5sp box to make 1st more useable.

In the BA the 3.45 or the 3.23 was dependent on the model variation and option. when the six speed was introduced (where the comparison is made) XR8's and FPV's were all fitted with 3.46 rear ends.

Gambit · 04-27-2006, 23:59

Quote:

Originally Posted by paulhowes

In the BA the 3.45 or the 3.23 was dependent on the model variation and option. when the six speed was introduced (where the comparison is made) XR8's and FPV's were all fitted with 3.46 rear ends.

In the ba you couldn't get the 3.46? diff with the 5sp manual box ( same as T3 box) unless you changed it yourself. All the 5sp manuals had the 3.23 diff afaik...

paulhowes · 04-28-2006, 00:26

Quote:

Originally Posted by Gambit

In the ba you couldn't get the 3.46? diff with the 5sp manual box ( same as T3 box) unless you changed it yourself. All the 5sp manuals had the 3.23 diff afaik...

Only going on what the dealer says he said standard models were 3.23 and all FPV were the 3.46 . base models incl XR8 with 3.23 had T5 trannies with much lower 5th gear and even after taking diff ratio differences in account were still a significantly shorter 5th gear than that in T3 and Pursuit 250's with the Tremec T3650. After feedback from customers ford decided to extend the 3.46 acrross the range to the XR8 at the same time as introducing six speed gearbox with taller 1st and 2nd.It was identified that customers in general through these previous models thought that these gears could be extended a little further and the gap filled between 4th and overdrive. I couldn't afford six speed so instead elected to narrow that gap as going to 3.23 would have extended 1st and 2nd but they didn't bother me and it would have made overdrive even more taller. I was more or less happy with the 1st four gears in conjunction with the ratio so went for pulling back the overdrive ratio. Horses for courses and it wont be for everyone and is not my ultimate setup but will do for now. I looked today its just touching 2100 in overdrive 100km/h and around 2250 at 110 Im happy with that. fuel economy seems unaffected to any noticeable degree after 3 tanks of fuel. Another aspect is that the vevehicles with 3.23 diffs were fitted with tyre and wheel combinations that gave them a smaller rolling diameter than that of the FPV fitted with 3.46. Take care, cheers

Gambit · 04-29-2006, 05:52

Quote:

Originally Posted by paulhowes

Only going on what the dealer says he said standard models were 3.23 and all FPV were the 3.46 . base models incl XR8 with 3.23 had T5 trannies with much lower 5th gear and even after taking diff ratio differences in account were still a significantly shorter 5th gear than that in T3 and Pursuit 250's with the Tremec T3650. Take care, cheers

The mk1 xr8 had the same box as the fpv vehicles (not the t5). I do agree with you that 5th gear in the 250's is worlds away from 4th but I like it (would rather a 6sp as you would tho) as at least I get decent economy with it & it still does the job in 5th when needed.

At least your happy with it as thats all that matters.