Rear End Options
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Cutting through all the myths about just what 240's and 740's came with what type of rear end and what Limited Slip or Locker differentials will actually fit these cars has been a long struggle. The following information has been submitted and compiled by various experienced Volvonuts over the years and will hopefully help you in making the right decisions.
If you have any additions or corrections, or if you can provide any photos that will help with these discussions, please email me.
Thanks, Dave Barton.
differences between a Volvo
1030 and 1031 Differential Case
Above photos are from Anthony Hyde's Volvo Differential page
Stealthfti from the Turbobricks Forum wrote:
There are measurable differences between a 1030 and 1031 rear end housing. A 1030 is about 10.125 inches from the rear cover mounting surface to the front of the pinion neck. A 1031 is almost exactly 0.5 inches longer.
it does seem all 1031s have
"ears" on the right side of the pumpkin (they are not machined on
240s). These ears attach to the torque arm on the 740
suspension. Justin's source for the info on the "ears" and the
1031 axle is Mike Knell, who authored the Volvo V8 swap information in JagsThatRun.
From reading posts on 4x4 chat groups, the Trutrac sounds like a great LSD, especially for street performance. The Dana Powr-Loc (which appears to be the LSD Volvo offered for standard towing packages) is also supposed to be a good, long-lasting differential (although quite expensive when new)..
UPDATE NOTE 07/16/06:
I installed a Trutrac in my 244 this
would like to share some info on that.
-from Mike Perry (mikep at Turbobricks)
Trutrac Installation notes for differentials using Speedo Tone Rings:
For the first tone ring car I installed a Trutrac diff into, I welded a speedo tone ring onto the diff. It was a big pain. I had to cut the ring apart and weld it to the carrier, then grind down the welds, which were brittle from conduction hardening, so I had to braze the cracks.
Then I did a Trutrac install for Michael Towery. I cut grooves with a die grinder and cutoff wheel. It was so easy and worked so well that I only do it that way now. The grooves need not be wide. The count just has to be the same. I think it's 12 grooves for the speedo. I'm not sure of the count for ABS. You can adjust the clearance by sliding the cover up or down, or by using a press in extreme cases. I have done probably 8 of the Trutracs in total, and the ones for 3.73 gears also work for 3.31 in most cases. The PN 912A411 in the first pic is in a 3.73 geared 1031 axle (my son's car) and the PN 912A588 is in a 3.31 geared 1031 axle. I also set up a few plate diffs and some locked (welded) for Rob's drift car. Maybe 12 Volvo axles total, not counting repair jobs.
Regarding differential part numbers... the Jeep front diff ("low preload", actually with a different hypoid angle) is a PN 912A314. I have done plenty of these, but they slip in turns with a big rear sway.
The old number for a Volvo rear with "high preload" is PN 912A411. I have done two of these. The new number is PN 912A588... better case material, high preload. I have done one. It is the number for high gear ratio numbers, but I think it went in a low number car.
One more bit of info: The diff manufacturers list a split in ratios at 3.51 or something, however I have never found a difference. I have measured diffs from Jeeps and Volvos with 3.31, 3.55, 3.90, and 4.11 ratios, and ALL were interchangeable. I recently put the new Trutrac PN 912A588 diff in a car with 3.73 gears, and have already put one in a car with 3.31 gears.
UPDATE NOTE APRIL 2008:
Jonas Borgegård of Sweden firstname.lastname@example.org wrote:
I have my own company in Sweden www.bakaxel.se and I sell mostly parts for Volvo. I sell rear axels and rebuilt BMW/ZF gearboxes to fit in Volvos and other parts.
If you wants ABS you can take the ring from the old differential and "move" it over to the Trutrac (PN912A588). You need to put it in an machine to take away some steel to be able to get it "on" and move out the pickup for the speedometer 2-3 mm. I have also made a CAD file and made a water cut metal "plate" that I wrapped around the Trutrac and then welded it together.
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