Identify my 242's rear end

I was under the impression 240s came with gearing of 3.31, 3.54, 3.73 and 4.1...The tag appears to read 3.91?

Possible swap or am I reading it incorrectly?

Both 1980 242's I have had were 3.91 gears. One had overdrive and the other did not. I would say it's probably stock.

Fair enough. Thanks for the help!

Some (most?) -82 manual trans cars had 3:91.
81-85 240 Turbo automatics also had 3:91.

wow I've never seen one of those tags in rust bucket Wisconsin

Is the 3:91 a relatively strong rear end?

There probably is some technical difference in strength between the ratios, but at this point, it's far outweighed by the condition.

Yeah, my 1980 was a 3.9 as well. Unless it came from a 260 (IDK if they used that ratio there anyways), it's almost definitely a 1030. "Strength" is about the same as any other 1030 - that is, it's not a 1031, and most of the guys doing something that'd break a 1030 would break a 1031 too.

The less multiplication the gears have to do, the stronger they'll be, but ^ what JohnMC said.

260's were 3:54 in rare stick shift form, the automatic ratio I don't know.

Redwood Chair said:

260's were 3:54 in rare stick shift form, the automatic ratio I don't know.

Click to expand...

Also 3.54.

Redwood Chair said:

260's were 3:54 in rare stick shift form, the automatic ratio I don't know.

Click to expand...

I had an 86-87 244GL parts car once that had a 3:54 in it. No idea if that was a special order or what. But I was surprised. I put it in a stock GT for a week. Was terrible. Would actually slow down in 5th gear because it just didn't have enough hp/tq to pull that ratio. I've hated b21f's ever since.

This is written for US spec cars:

M46 gas 260's were 3.73. Bw55 were 3.54, as were Diesel M46 260's and 240's. Diesel autotragic was 3.31.

1976 (possibly 1977 as well) 240's, M45/46: 4.10:1 or 3.91:1; Bw55: probably 3.91, could be 3.73
1978-80 240 M45/46: 3.91:1, Bw/Aw55: 3.73 for 1980, probably 3.91 for 1978-79
1981 240: M46 B21F/FT with Bosch ignition, as well as Aw55 B21F with Bosch: 3.73; B21F-MPG: 3.54 if M46, 3.91 if Aw55.
1982 240: B21F-MPG and B21F-LH, same as 1981 MPG, except that Aw70 became available. B21FT actually was supposedly 3.73 with the Aw71 in 1982, at least, according to the greenbooks.
1983-on cars: B23/230F: M46/47, 3.31:1; Aw7x, 3.73:1. B21FT: M46, 3.73:1, Aw71, 3.91:1.

This also assumes that the cars were either built at Torslanda or in Belgium. If Halifax, anything goes.

Re: a 3.54:1 rear axle with a B21F, I could see that, if the head had an L cam in it. The B cammed B21's have enough oomph to deal with a 3.54 and a .79 gear ratio. After all, swedishiron.com drove a '79 245DL that he switched over to a 3.54 from a '76 264GL Bw55 car for many years. As long as you kept the speed above 45 mph in OD, it would pull uphill grades without losing steam. Otherwise, yes, it can be as slow as a M-cammed B23F or B230F/M46 car with the stock 3.31 rear axle. Great for mileage and top speed, not great for acceleration. You know it's bad when you're doing 4500 rpm in a B230/M46 245 up a hill in 2nd gear and an Aw70 equipped B23F 245 is keeping up with you and actually trying to push you harder going up said hill.

From my Hollander (62nd edition):

Please note I left the pictures as large as possible to make them more readable.