The old "volvo diff into celica conversion"

[The Witzl]

TT 912A588 is the part number for the rear trutrac unit. The front one is TT 912A585. Look for the right one but both will work.

Stidnam.... just how important is it to have the rear unit instead of the front unit?

The reason i ask is that the prices are significantly different:
TT 912A588 = US$450
TT 912A585 = US$360

This is where i'm looking to buy from... and they list the TT 912A588 as the "27 SPLINE PINION, 373 & UP, VOLVO REAR" specific part.
http://www.drivetrainspecialists.com...ruetrac-1.html

I'll ask the guys in the USA to make sure, but would appreciate your comments as you seem to know what you are on about!


I think i've already worked out the correct part numbers for F-series and G-series diffs.... and have even found the part number for the EARLY hilux diffs

Early G series - TT 913A611, "74 TO 85, ALL RATIOS, REAR"
Later G series - TT 913A610, "86 TO 96, ALL RATIOS, V6 & TURBO ONLY, REAR ONLY"

I've emailled the guys in the USA to confirm... hopefully they can clarify.

Jack - can you check with your contact as well regarding the above part numbers for the G series and Dana 30 volvo diff? Want to make sure we are going to get the best deal possible of course, and $100 difference is worth looking into.... and that we order the correct G series centres.

I think its worth checking into the two different G-series centres, as i have seen a few people comment that the Torsen centres dont fit into the early model hilux diffs without some mods to the crown wheel spacing and pinion gear.

[The Witzl]

group buy started.
See here:

http://www.toymods.net/forums/showthread.php?t=49501

[stidnam]

have a look on the volvo forums http://forums.turbobricks.com/ as there is a few threads which discuss this. Search for the part number.

From memory the whole 3.7 upwards stuff about the centres which supposedly don't fit the 3.3 - 3.7 ratio diffs doesn't really matter with the volvo diffs as the carriers are the same. Bit rusty on this so research this before buying anything.

[fade-e]

guys a bit off topic, but the lower the ratio the higher the top speed and the higher the ratio the better in acceleration.

is that correct?

cheers

[web]

The version for the rear diff has a higher "preload" than the front diff. From Volvo forums I gather the front diff does fit, but offers lower performance.

Technically, a gear type LSD does not have preload. Torque bias is a more accurate description. It supports a greater L/R grip difference (ratio) before spinning. You may not notice that at the drags, but you will in hairpin type turns. The front diff and even the older rears (the current design is a strengthened and updated one) are more likely to spin the inside wheel in tight hairpins.

So yes, you want the rear version.

[web]

guys a bit off topic, but the lower the ratio the higher the top speed and the higher the ratio the better in acceleration.

is that correct?

cheers

Generally yes, with lower and higher being the numeric ratio.
Confusingly, a lower number is called a "tall" ratio, and a high number is called a "short" ratio.

Better acceleration with shorter gears (= higher numeric ratio) works up to a point, where it only results in burning rubber instead of accelerating. If best acceleration is your only concern, you want the shortest ratio where you can still get the power down. You also need to take into account that shifts take time, and with shorter gears you will need more shifts to reach a certain speed.

[fade-e]

well for the W58 gear ratios and wheels ill be getting (16/225/50), max RPM being 6500 top speed would be...

3.73 - 265
3.93 = 250
4.1 = 240
4.3 = 230

i think i might just stick to stock 4.1... good top speed for track and will also give me good acceleration...

cheers

[Toy77]

if you are interested in drag racing, more important than top speed, is the terminal speed in 4th gear.

mine with the r154 tops out at something silly - up near 300km/h - but 4th is perfect for the speedsi want to run across the line....

Probably not too many race tracks you want - or will need to be in 5th gear for i wouldn't imagine...

The bestthing i found when going frm4.1 to 3.9 was the extra legs in 1st and 2nd gear - as well as bit more loading to make the most of the turbo....


Cheers
Stew

[fade-e]

i will take the car to the strip once in a while, but more of a track person... also i will be getting 1st 2nd and 3rd gears changed to dog and semi so i can play with the ratio then if i want to change bottom end acceleration

then there is NOS....

so yeah...

cheers

[The Witzl]

stidnam - turbobricks forum wont let me search or register... their little anti-spam thingo seems to lock up the page and it just doesnt load. So me searching = fail.

[The Witzl]

Ok i just picked up the volvo diff from Smokey tonight... and fark me it weighs a TON!
Anyway, tried finding this ID sticker... couldnt find it anywhere. There was a sticker about 15x50mm on the left hand axle tube on the rear, but was worn out with nothing printed on it, and it just flaked off.

I did the rotation trick... and its definitely ~3.7:1 ratio.

The only other identifying mark i could find was the following, moulded into the casting of the centre carrier to the bottom right of the rear cover plate.

It says "VOLVO 1022558" from the best i can tell...



also, wtf are those things hanging off the brake lines??




I guess to be certain i will pull it apart tomorrow and measure the actual gears to confirm if its a 1030 or 1031, and get the exact gear ratio.

[fade-e]

there has been quite a bit of talk ont he conversion and the centres, but what the the specs for the discs themselves?

anyway i looked at the DBA site and found the following...

Rear Disc mm
Diameter 281
Height 73
Thickness 9.6
Min. Thickness 8.4
Center Hole 68
Bolt Holes 5

all in all its a good sized disc, though i dont like the thickness

has anyone done an upgrade on these? different discs and calipers with spacers, etc?

[TA22 1MZ]

also, wtf are those things hanging off the brake lines??

brake line distribution block. should be a single line that runs off the front of it to the master cylinder. I think they are also the bias valve.

Fadi, no need to worry bout brake upgrades mate, nice size rotor and twin spot caliipers, its a bloody good factory setup.

[web]

That's definitely a 1031, it has the late style mounting ears on the diff housing. Those ears are for 740 control arms, but unused on a 240. Same casting though, which tells you it's a 1031 because the 740 never got a 1030.

So none of the 1030 castings have those threaded ears.

Note that early 1031s did not yet have those ears because the 7-series didn't exist yet. So there ARE 1031s that don't have them, just no 1030s that do.

By the way, a lot of the weight of these rear ends is in the disc brakes they come with. Just taking the discs off will reveal the relative lightness of the rest of the thing.

[The Witzl]

Web, thanks for the awesome info as always.

I just spoke to Eaton, the makers of the detroit truetrac diffs, and they said that the more expensive 912A588 part number is specifically designed for the Volvo diffs, with a high performance application in mind. They told me this model has a pre-load set into it, which im lead to believe means that it doesnt have to spin one wheel first before transfering torque back to the other wheel - IE, will spin up both wheels straight away.

Apparently the 912A585 doesnt have this pre-load, and is designed for the front axle and wouldnt be so good for the vovlo rear end. They strongly recommended the 912A588.