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Old 09-20-2015, 05:07 PM   #1
scottie.tooley
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Default Speedometer Reading 4x Too Fast

I purchased my 1991 Volvo 240 having never driven it. The car had sat for about a year because the rear pinion bushing had exploded. I had the care towed to a Volvo specialist, who ended up replacing the entire axle with one from a 1992 240.

Once I got the car back and starting driving it, I realized the speedometer is way off. It seems to read almost 4-5 times too fast. At 35mph (estimated in traffic), it maxes out the 120mph speedometer. I've done lots of searches, and most times people seem to have trouble with the speedo not working at all or intermittently. However, I haven't read of anyone having one that goes too fast.

Now, my first thought was that the 1992 axle has 4 contacts on the diff to sent the signal, instead of the 1 contact on the 1991. But, everyone says that the axles should be the same. Has anyone else run into this issue? I don't imagine it is an issue with the speedo gear, as how would it break and read 4x fast? Could corrosion on the speedo board be causing increased signals to the unit?

Of note, the odometer is also that much faster. So, if I've driven 800 miles, the odometer has put on around 2,400.
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Old 09-20-2015, 05:22 PM   #2
culberro
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They probably swapped a rear end with an ABS/48 tooth tone ring on it instead of a non-ABS one using a 12t ring.
Either open it up and cut out three teeth... Then skip one.... Repeat. Or get an ABS speedometer and swap it into the cluster.
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Old 09-20-2015, 06:48 PM   #3
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Originally Posted by culberro View Post
Either open it up and cut out three teeth... Then skip one.... Repeat.
I've heard this advice given before, but I'm not so sure it will be quite that easy on the 92's rear axle.

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Originally Posted by culberro View Post
Or get an ABS speedometer and swap it into the cluster.
This is not quite so easy as it sounds either. The 92-93 speedometer does not fit the 91 cluster. Even going to an entire new cluster is more than just swap.

The easiest way from A to B is to find the "converter" from a 91 ABS car and wire it in between the new rear axle and the speedometer. It looks like this:



The ABS "tone ring" is a gear.

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Last edited by cleanflametrap; 09-20-2015 at 06:53 PM..
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Old 09-20-2015, 07:08 PM   #4
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Good to know Art! I didn't know that ABS cars were only the later years, I also didn't know about the gauge clusters being different. I guess that's what I get for playing with the older cars so much

It shouldn't be that hard to remove the teeth on the speedo gear. But the converter is probably a much easier solution!
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Old 09-20-2015, 08:50 PM   #5
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Just swapping the entire cluster should work fine. The later cluster has the same connectors on it and a 1991 240 without ABS does not modify the signal coming from the rear axle. It should be plug and play with a K39200 or K40168 instrument cluster.
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Old 09-20-2015, 09:08 PM   #6
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Just swapping the entire cluster should work fine. The later cluster has the same connectors on it and a 1991 240 without ABS does not modify the signal coming from the rear axle. It should be plug and play with a K39200 or K40168 instrument cluster.
I know it should be, but it isn't. The plugs are purposely pinned differently so this does not occur. It doesn't prove to be a big roadblock, but they do not interchange plug and play.
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Old 09-20-2015, 09:19 PM   #7
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Which connector needs to be re-pinned? I know someone that is trying to get the ABS cluster to work with an ABS rear axle on a 1990 240. Is is a simple swap of positions on a connector?
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Old 09-20-2015, 09:21 PM   #8
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Quote:
Originally Posted by 2manyturbos View Post
Which connector needs to be re-pinned? I know someone that is trying to get the ABS cluster to work with an ABS rear axle on a 1990 240. Is is a simple swap of positions on a connector?
Yes, the ground and signal pins on the speedometer L-shaped plug. I can only speculate Volvo did this on purpose to keep from powering up inaccurate (however wildly so) speedometer gauges. Let me find an old post, or the wiring diagram.



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Old 09-20-2015, 09:26 PM   #9
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Wow, if it is that simple, what an easy solution.
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Old 09-20-2015, 09:34 PM   #10
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Quote:
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Wow, if it is that simple, what an easy solution.
Things are always easy when you know how.
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Old 09-20-2015, 10:17 PM   #11
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I discovered the speedo connectors were different a few years ago when I did the lh2.4 swap. A proper wiring diagram would have been helpful. I just moved the wires around until the speedo read correctly
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Old 09-21-2015, 02:32 PM   #12
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I use a Dakota Digital speedo corrector on my 88 745GLE 5.0.
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Old 09-21-2015, 02:52 PM   #13
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I like the converter solution, seems elegant, no need to re-pin, keep your perfectly good cluster, buy a part for stupid cheap that has no real value except to you or some other crazy tweaker that happens to have an 86-91 240 (or non ABS 740/760 probably?) with an ABS 48 tooth tone ring in it.

The tone ring isn't always a "gear" if it has a G80 or LSD and ABS. I've had two clutch LSDs from ABS cars now and quite a few G80s.

Now just to find someone wrecking out a 91 ABS 240...2manyturbos/billy780?
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Old 10-07-2015, 07:13 PM   #14
scottie.tooley
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Default Thanks Everyone!

I posted this weeks ago, but forgot to subscribe, so my email didn't alert me with replies! I'm definitely going to try the converter route first, as it seems to be the easiest. Hopefully overdriving my speedo for the past 3 months hasn't damaged anything.

My so-called Volvo expert that swapped out the axle pretended not to know anything about it. I asked him if he knew way the speedo was way off after the axle fix, and he just said "don't worry, we can fix that for you when you come back" and then bashed a few other Volvo guys in the area.
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Old 10-07-2015, 10:39 PM   #15
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Quote:
Originally Posted by 2manyturbos View Post
Which connector needs to be re-pinned? I know someone that is trying to get the ABS cluster to work with an ABS rear axle on a 1990 240. Is is a simple swap of positions on a connector?
While we were all passing judgement on which approach is easier, I should have mentioned how that really depends on which part is easier for your situation.

Maybe it depends more on which one is easier to obtain: the converter which best I know ONLY comes in non-ABS 91 240s, or a 92/93 cluster. Both require some wiring splices or pin swapping, but in the end the challenge is not that, but locating the parts you need. Keep your options open as regards availability, quality, and price.
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Old 10-22-2015, 01:19 PM   #16
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sorry to hijack this a little, but am i understanding this correctly...

if i can find one of these converters from a '91 non abs 240, does that mean i can fit a g80 locker in my axle without cutting the tone wheel, which i have been told can be tricky to get to work?

thanks!
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Old 10-22-2015, 01:23 PM   #17
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^You'd need the converter from a 1991 ABS 240. Then, you could use the speedometer same as usual in any '86-'91 car.

I think you need the sensor from the G80 car with its aluminum diff cover?
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Old 10-22-2015, 01:30 PM   #18
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I've got a big list of stuff to find at local junkyards. This goes on the list, along with some cheap 80's Recaro's, and a new plastic mechanical fan cover. If the sensor proves to be a unicorn, I'll then go the newer cluster route.
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Old 10-22-2015, 01:34 PM   #19
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I can't quite tell from the photo. Am I seeing "3 540 017" as a part number on top of that converter? Might be worth a shot to try Volvo, Amazon, or eBay for the part.
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Old 10-22-2015, 02:14 PM   #20
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i read it as 3 540 017 too, ill see if i can find someone who has one who can get all the proper numbers.

kjets, thanks for the info. this would actually be going in a 79 244 so i will 100% need the diff cover with the g80!

i am still working on the speedo problem.
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Old 10-22-2015, 02:46 PM   #21
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Quote:
Originally Posted by howarddj View Post
i read it as 3 540 017 too, ill see if i can find someone who has one who can get all the proper numbers.

kjets, thanks for the info. this would actually be going in a 79 244 so i will 100% need the diff cover with the g80!

i am still working on the speedo problem.
In that case, none of the above is going to work for you unless you change the dash to accommodate the later style instrument cluster.
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Old 10-22-2015, 05:15 PM   #22
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Drive four times faster. LOL.
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Old 10-22-2015, 06:17 PM   #23
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Found listings for Volvo 3540017:

Control Module ABS -91 Item #10.
Volvo 240 88-91

Impulse Converter- Volvo 3540017
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Old 10-22-2015, 07:31 PM   #24
scottie.tooley
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Quote:
Originally Posted by lummert View Post
Found listings for Volvo 3540017:

Control Module ABS -91 Item #10.
Volvo 240 88-91

Impulse Converter- Volvo 3540017
Thanks! You've just earned a screenshot in my OneNote! Tell all your friends, it's kind of a big deal!
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Old 03-04-2016, 10:27 AM   #25
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Quote:
Originally Posted by scottie.tooley View Post
Thanks! You've just earned a screenshot in my OneNote! Tell all your friends, it's kind of a big deal!
i have been installing a 940 instrument in my 242, with 960 dashboard+++... of course it reads wrong, to little,
i have the 12 "tooth" speedoring... will this relay\converter take care of that problem that way or some other solution to convert the speedosignal to 48 as the 940 have?
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