T5+3.55 ratio feedback

[trav68]

Gents,
For those considering it I would recommend 3.55 ratio with a T5 box. I am using a 6 cyl T5 box which has a fairly short 1st ratio but it is still fine and highway speeds are about 2000 rpm which is below where some drone sets in ( about 2200 - 2400 rpm) hence I did not want to go higher to 3.8:1.

As per the other thread I went from a 3.25 (as I previously ran a C4) and this new ratio definitely suits the car better. It is not a big change obviously but I had a few reasons for doing it ( original diff install was weeping slightly from gasket/copper seal washers which annoyed the crap out of me, previous diff was only part in the build I farmed out so wanted to build it myself and learn, and also had a ready buyer for my very low km 3.25 setup).

So in summary 302+Falcon T5+Home built 3.55 Motive Gears/Eaton Truetrac=

Regards,
Trav

[ozbilt]

That one may suit you, but there are a lot of differing ratios in that series of box & you have to also consider what is in front of it (engine & if modded).

The car that is my avatar has a Paxton blown 5.0 EFI with a T5 & ran 3.25 rear gears. It is a jet & also has really good top speed (useful on the freeways of the USA)

One size does not fit all.

[boofhead]

Good to hear peoples positive experiences. I also am running a T5 with 3.55:1 rear. It is not a bad ratio for highway use - now my T5 is after market T5z which has a tall first gear and high over drive - so I personally am thinking a 3.8:1 or even a 4.11:1 would be better for my engine generally. Will I change it - hmmmm - most likely at some stage when the money tree is blooming again at which time I will do the gear myself.

[boofhead]

Ozbilt

[trav68]

Yep agreed that is why I stated the origin and spec box

[shaun071]

Interesting- I had an AU XR8 ute that had a t5 and 3.45 rear and was very sweet all round.

[DD289]

Thanks for starting the thread Trav. To put things into perspective the rear tyre size, specifically the diameter is also worth mentioning. Personally I'm still planning to run a 3.25 rear behind the T5z from Modern Drivelive with 0.63 od. With a 25" rolling diameter rear tyre, in theory this will have the stock 289 doing about 2100 at 75mph (freeway cruising) in 5th, coming off about 3300 in 4th. And yes, good to avoid that drone at 2200-2400 that my thing also gets. 3.55 would have me sitting on 2250 at that speed, and I suspect that would drive me nuts on a long run.
A lot of my preferred driving is on country roads (not necessarily in od) so I also want to avoid revving too high in 4th at, say, 65mph. As an example, the revs at that point with 3.25 vs 3.55 rear with my setup would be about 2800 and 3100 respectively. My disclaimer is that this is all theory, relying on an online RPM calculator. The the real test of course will be driving it home from Douggo in a couple of months time, assuming all goes to plan!

[boofhead]

Agree tire size is a factor. Your choice sounds ideal for your engine. You have done great research with consideration of your engine's characteristics coupled with your driving style and intended car use, I am sure you will be spot on.

[DD289]

Thanks Boofhead. And Kerry will be sitting there grinning because it's what he suggested off the top of his experienced head in the first place

[DD289]

Got the 3.25 Eaton Truetrac happening this week so it's ready for operation stick shift. Short run home showed good signs it's all working sweet. Even behind the stock A code and C4 I was pleasantly surprised with a little chirp into second and a slight kick to the side. Can't wait for the T5, even if 9 out of 10 blokes I meet reckon I'm mad going with a manual box.
BTW, I did hear there are some Chinese knock-offs of the Eaton product to be wary of. Maybe some others can offer opinion on that one.

[trav68]

I think that might be in relation to Pro-Comp centres as I think they have branched into diffs too.

The fun factor with the manual T5 is 10 fold compared with the 3 speed C4 (in my humble opinion) don't listen to the nan sayers.... Good luck with the T5!

Cheers,
Trav

[shaun071]

Yeah. Speedmaster79 torque worm lsd. Only about $100 less than a genuine trutrac.

[DD289]

Thanks Trav and Shaun, both comments are consistent with what I have heard. Amazing what people do to save $100.
I'm not concerned at all about any comments others make about changing to a manual. Each to their own. But for me, since manual early Mustangs seem to be quite rare, I bought mine that ticked all the other boxes, with the intention of converting it asap. I was thinking of selling the C4 and associated bits, but may be I'll hang onto it in case my needs change in the future.
Who knows, I may want to drag race it... Unlikely
It may become my daily drive... don't think so.
I may get lazy... I'd be surprised.
One day it may be worth restoring an A code coupe to factory spec... Um, time will tell.
Or, I may get old and still have the 65 coupe... I certainly hope so.
Yep, I better keep all the Cruise-o-matic gear in the shed