Cheap diff upgrades - Ford Forums

Troutman · 03-12-2004, 18:36

As many of you know I am planning on replacing my T5 with some sort of heavy duty auto tranny. The big problem is that I'd lose a lot of performance if I did it now (and I can't throw afford any time/money for it just yet anyway). I've decided that to make the car better to drive in the meantime, I should start with the diff.

What I'm wondering is whether upgrading the diff gears is as simple as getting a cheap R31 Skyline or similar diff and throwing the gears into my existing housing? I think QuikCorty did something similar when he upgraded his, except using VL gears?

I don't have a need to convert to LSD at this stage but will have to do it later.

Depending on the R31 ratio (I've heard 3.7 or 3.9 from different sources) I'm aware that I'd have speedo accuracy problems as well which could be tricky to rectify.

Any opinions or advice appreciated.

PS the existing diff is a 3.08 28 spline ED item.

OED666 · 03-12-2004, 18:52

I will forward you a PM that Rollin sent me, i am pretty sure he has a skyline diff centre in his, with 3.89:1 Ratio. If you are keeping it auto, i would go 3.7:1...

there is something you can get for about $200 to fix your speedo up to suit those diff gears, i am not too sure where you get it, i have only just heard about it

Troutman · 03-12-2004, 22:35

Fantastic thanks a heap matey! I'd be happy with either ratio - I'm not after serious performance at this stage, just drivability.

One thing I don't get is how they managed to use a 2.77 LSD centre to fit into a 78 series diff housing. If this is possible then I'll have to bash my head against a wall for a while... I sold a complete 2.77 LSD in perfect nick for $30.

Anyway, I'll start looking into it. Thanks again!

OED666 · 03-12-2004, 22:54

No worries,

3:7.1 would be a great general diff ratio, i will be getting 3.45:1 LSD very soon, i would get a 3.7:1 but i have to stuff around to get the right speedo gear. i think the speedo gear for say 3.7 or 3.9 doesnt fit in the original spot for the speedo gear, if you get wot i mean...

OED666 · 03-12-2004, 23:15

large_trout - keep an eye on this thread

wanted - speedo corection box for E-series

XRated · 03-12-2004, 23:18

Jack, you are in a very similar position to me. I am wanting to whack in some 3.7s from a Skyline/Pintara but am concerned about a couple of things.

The cost,
What I actually need to aquire,
Drivability at HWY speeds,
And finally, I have heard rumours about the gears making the diff noisy. Dunno how true that one is, but it'd be great if someone could clarify some or all of these points.

I'm just wondering if it's as simple as going to a Nissan wreckers, getting the gears to suit and then getting a diff place to fit them. I'm sure there are other parts you need but I have no idea what they are...

Good luck bud!

Troutman · 03-13-2004, 03:12

The cost will vary, but obviously there are just the parts and the labour. Someone on the R31 forums is offering 3.7 diff gears for $150. I've found absolutely nothing on the Trading Post or Ebay. Labour would be a few hundred but I'm going to have to get a precise quote, probably in the coming week.

I wouldn't worry about highway drivability too much, unless you have a loud exhaust and droning is an issue. With the T5 manual and 3.7 gears, the rpm @ 100 is almost identical to a stock 3 speed with 2.77 gears! Take-off is not so similar.

Remember the 4 speed auto has a taller top gear than the T5 manual.

Regarding noise, there is no reason why that should be an issue - not unless the gears are worn, or the fluid level is low, or the installation improper. The most reputable diff place I know of in Melbourne (Preston Autos) use Skyline gears. Incidentally my friend got quoted something like $1500 for his VS, using new gears and converting to LSD. Using recoed parts is much cheaper, but I'm aiming to do this for next to nothing. I half wonder if it can be done in the garage.

Good luck to me.

OED666 · 03-13-2004, 04:41

XRated - as i may have said earlier in the post, (i cant be bothered scrolling up to read it, even though by the time i have typed this i could have) Rollin has 3.89's and does a touch over 2500rpm at 100k, well from memory anyway.

3.7 would be a good ratio, i am goin 3.45 as its goin to be a straight swap over.

EFJase · 03-13-2004, 05:26

Rollins car is a manual but aint it?
So a 3.9 in a 4spd would be higher again. Probably closer to 2600-2700rpm.

and for those who dont now;
Divide current rpm at what ever speed, then multiply it by geasr wanted.
ie (using random numbers) 2500rpm/3.08=811.69 811.69x3.7=3003 rpm

I am also inerested in getting a 3.7 diff for my EB, so if u find a cheap way, let me now!
I was told by a guy who goes through a few diffs :) to expect $600 for single spinner gears, drive in drive out. Which isnt toooo bad

OED666 · 03-13-2004, 05:55

Yea Rollins is a manual.

This week, my brother had new bearings put in his LSD, (commodore) and it cost him $725. $1290 for a complete re-build. A brand spankers LSD from Holden $1700 and an open wheeler was about $100 cheaper.