Rear End Options
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Derek Walker wrote that while in the process of examining different options for an LSD for his '89 745 GLE (equipped with a 5.0L Ford engine and 4.10:1 differential), he checked with Reider Racing regarding the Truetrac per the recommendations here. Reider responded that his 1031 Volvo housing would NOT accept the Truetrac LSD due to slight dimensional differences from the 1030 housing. It seems they had had a few returns from Volvo owners due to incompatibility issues. It's not clear if the issues are unique with the Truetrac LSD or the 1031 housing.
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
Truetrac sounds like a great LSD, especially for street
The Dana Powr-Loc (which
appears to be the LSD Volvo offered for
packages) is also supposed to be a good, long-lasting differential
(although quite expensive when new)..
tuff240 from the Turbobricks Forum wrote:
The differential units are all the same up until they changed them for the speedo tone ring. The only difference between a 1030 and 1031 is the housing itself and the ring and pinion. The differential units can be swapped back and forth. The ring and pinion cannot.
The later model cars (86 and up), which all have speedo tone rings, are believed to all be 1031's. A Truetrac unit going in a car that requires a speedo tone ring will be different only to fit the tone ring. You can still swap tone ring or no tone ring differentials from 1030 to 1031. The only problem will be that you won't have a working speedo if you need a tone ring and install a diff that does not have one.
AGAIN, the major difference is the Ring and Pinion. The differential units come in 2 sizes depending on what Ring and Pinion you have or want. One will fit 3:73 and up, one will fit below 3:73. Make sure you pick accordingly in case you ever want to change gears. For example, you cannot change from a 3:91 ring and pinion to a 3:31 ring and pinion without changing the differential unit. This goes for stock oem diffs and TrueTrac diffs as well.
*EDIT The pinion bearings are also different between a 1030 and 1031. So make sure you get the right pinion bearing for whatever rear end you have.
I abused a 1030 rear end with 200 rwhp for about 15K miles with NO problems whatsoever. But keep in mind I have no personal experience with 700 series cars, just 200 series cars.
UPDATE NOTE: (07-16-06)
-from Matt Dupuis
I installed a Truetrac in my 244 this
would like to share some info on that.
Because my car is a V8, I chose to use a 3.31:1 gear ratio, so I ordered the low-preload diff for the 3.54:1 and down (PN 912A374). I'm using a 1031 axle from an '86+ car, so it's got the tone ring and speedo drive (I had planned on using this with my Megasquirt for traction control at a later date). At the same time, Dale Walmsley ordered a high-preload diff for the 3.73:1 and up (PN 912A411), for his 122 which we installed into a 240 1030 rear axle.
When I got my rear end apart, I thought to measure the carriers to see if I needed to buy any different shims. To my surprise, I needed to add about 0.120" to the ring side of the carrier and subtract that from the other side!!! Since the factory shims are about .060" each, that meant I'd have to machine material from the carrier to get it to fit. Obviously this wasn't the right part for the car.
So I borrowed Dale's Truetrac and measured. It was within .001" of my Volvo diff carrier, so I installed it using the original shims and new bearings, and the gear lash was even better than it was before I pulled the old one out.
Again, I used a 3.73 and up TrueTrac (p/n 411) with my 3.31 ring and pinion in my 1031, and all fit perfectly well. I've also installed the same diff into a 760 with a 3.73 and it fit just as well.
The taller gears (3.54 and down) have a larger diameter pinion to accomodate more teeth, so the ring gear must be moved further offset from centerline in order to keep the thickness of the ring gear consistent with shorter ratios. Many manufacturers do this by moving the flange on the diff carrier outboard for the "highway" gears, but it seems that Volvo, in the 1031 at least, used a thinner ring gear instead, and kept the differential carrier the same for all ratios. I can't speak for the 1030 model diff, since that's closer to a true Dana 30. They might use thicker ring gears and offset flanges for the 3.54 and down (if they were ever delivered with those ratios).
Another thing that occurred that you should watch for.... the pickup for the speedo may drag on the Truetrac. My 240 had a light drag, and I didn't bother doing anything about it, but the 760 I did had a HEAVY drag, so I had to clearance the sensor to clear the diff.
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