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I knew that, after swapping in a J-type M41 for the BW35 my "71 142E came with, the speedometer was pessimistic. The other day I drove it side by side with my 245 - my daughter driving - ,and we found that the 142's speedo showed 56 when the 245's showed 65 mph: and we know the 245's is accurate. That was much more of a discrepancy than I expected. (No wonder I was getting only 20 mpg) The potential, though only partial, solution I can think of so far is the swap the 20 teeth speedometer drive pinion in there now for one with fewer teeth. The smallest number of teeth available is 18. I contacted Duane Hoberg, the OD Guru, and he was kind enough to check his parts bins, but could only come up with a 19 teeth drive pinion. I have contacted two suppliers in the UK who supposedly have the 18 teeth drives - no reply yet. While I wait for them: does anyone have any other solutions? Does anyone have an 18 teeth drive pinion he'd like to sell or swap for 20 teeth -- know of a US supplier? Sure, I could always tape new numbers onto the speedometer face, but that's a bit of a cheat I think. BTW, I running 185/75/R14s at the moment and 195/65/R15s in summer.
Thanks,
Bob S.
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posted by
someone claiming to be shayne
on
Wed Jan 4 06:15 CST 2006 [ RELATED]
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Don't rule out the '85 and earlier 240's M46/J-type for experimentation.
A friend had swapped 3.73 for 3.31 in his '82 242 after a blown M46 third gear and Gutrag(sp) swap, so I asked for his drive gear just to see if it was the same shape and if it would work in my M41 J-type.
Pink in color, perhaps originally red? Sorry, I don't remember the tooth count, it's written down somewhere, but all the other gears I have, black and green, are now marked and accounted for.
My 122 sedan now has 3.73 (LSD) and an accurate speedometer!
3.73's a little long-legged, 3.93 is was not available for my axle-shaft tooth-count.
I think the D-types have the same drive-gear configuration as M40's, like B20Paul mentioned, which would it make it much too short for the M41.
Best,
Shayne.
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My D-type M41 uses the same gears as M40s use. Are J-type M41's that different? (I've never seen one.)
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Yes, the shaft is longer and the gear is much bigger.
BOb S.
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Bob,
You should check your odometer first. I've been in situations where both
the speedo ratio and the speedo itself were off.
Once you get the Odo right (or close) then it is valid to work on the speedo.
But if you correct a speedo error and in doing so screw up your odo, it is
sort of counterproductive.
I'll check my gears. I have a few.
--
George Downs Bartlesville, Heart of the USA!
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George,
Fair enough. I've mucked around with 544/122 speedometers a bit, but haven't done much with the ones in the 140s, except for replacing bulbs and taking a non-functioning spare apart to see how it was put together. BTW, this is the original speedo that came in the car with the BW35. Do you have, or know where I can find, more information on how to change the behavior of the odo/speedometer in relation to the revolutions of the wheels?
Oh, and while I have you attentiuon, a totally unrelated, question: do you happen to know the correct Spanish term for limited slip differential? I'm thinking "diferencial de deslizamiento limitado". (Yogui, are you there?) I'm trying to convince a Spanish-and-Portuguese-only nephew that, for his purposes, he'd be better off with rear wheel drive and an LSD than a 4WD, smallish SUV.
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Well, I guess we are starting off with the ratio of the speedo/speedo cable
to the wheels and really the ratio of the speedo/cable to the driveshaft.
All I know to do is change to different colored gear on the tranny output
shaft although possibly the spiral gear ON the shaft may be changeable too.
(Definitely not as easy though!)
The accuracy there can be judged by the behavior of the odometer. If it is on,
you have the right gears. If not..... (Now there may also be different ratio
speedometers - I've seen them marked 0,99 and 1,03, for example - crazy
Europeans don't know a comma from a decimal point) Anyway that would make
a 4% error where you have more like a 20% error. If you have different
speedos you can swap that might be fun to try. That and the gears are all I
know for that.
Now once the odo is correct you can start in on the speedo. Dirt in the
coupling will make it fast and jerky, and dirt in the bearings will make it
slow. Tightening the spring will make it faster and loosening will make it
slower. Best starting point is to start with it clean and lubed with the
lightest machine oil you can find - NOT any kind of penetrating oil!!
If you can find specs of rpm vs mph and have a way to drive it at a constant
speed that would make it easy, just like a speedometer shop. Do we ever do
anything the easy way?? Probably rarely at best. (Sorry about the pessimism
but ¿Whó started this, anyway?)
About Spanish for limited slip - dunno. 4WD is «doble tracción». Maybe
something like double engagement or firm engagement - perhaps «diferencial
de embrague firme» or some such. Terminology varies from country to country
also. Or maybe you could go from what it does - «diferencial que no pierde
tracción», differential that doesn't lose traction. How about «Positracción»??
(I can manufacture words in Espanglés in a hartbeet!)
Good luck - I think you're right.
--
George Downs Bartlesville, Heart of the USA!
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Some random thoughts on the speedometer problem.
First, we probably have a match that never existed in "stock" form, at least not in the US market... I'm guessing a 4.10 diff, matched to a transmission speedo drive that "wants" a 4.56 rear gear ratio to work accurately. Therein would lie an approximate 10% inaccuracy from the get-go. ((Not that early 140 speedometers were all that accurate to start with... IIRC, they didn't even tell you which part of the "slash" on the ribbon was supposed to be the accurate part!))
Having said all that, my 1972 140 parts catalog has very clear references to the existence of many different drive gears for the M40, M41, and BW35's, well outside the 18 to 20 tooth range. The M40 part numbers are:
380164-4 (16 teeth, 142 & 144 excluding USA & Can)
380166-9 (17 teeth, 142 & 144 USA & Can, 145 chassis #9200 and up)
380168-5 (18 teeth, 145 up to chassis #9199)
The same catalog lists 13, 14, and 16 tooth gears for the BW35, to wit:
670131-2 (13 teeth, 142 & 144 various chassis numbers)
672886-9 (14 teeth, 145 various chassis numbers)
380164-4 (16 teeth, 142, 144 & 145 various chassis numbers)
Since there is a crossover part number (the 16 tooth in both tranny's), I would therefore assume that all M40 and BW35 speedo drive gears will physically interchange... but I don't know this for a fact.
Unfortunately though, when you get to the M41 (at least WRT to the 1972 140), there is only one drive gear listed, and it seems to be unique to the M41. Interestingly enough, there is NO gear tooth count for this part number, 380753-4. Prolly the 20 tooth? In any case, no clue as to whether it will physically interchange with any of the above 13 to 18 tooth gears above.
So the 20 tooth drive gear you are currently using came with the M41, yes? Do you still have the speedo drive gear from the automatic? If so, the obvious questions... how many teeth on it, and will it physically fit in the M41?
And finally, a comment on your 142E, as delivered new. A rompin', stompin', 10.5 to 1 B20E, with a stinking automatic????? That had to be a pretty rare combination, I would think? I can honestly say I have never seen one. Of course, they were also slipping (no pun intended) automatics into a few high compression (1970/71) 1800E's at that time, so I guess the '71 142E auto would have to have been a distinct possibility.
Gary L.
--
1971 142E ITB racer, 1973 1800ES, 2002 S60 T5
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Thanks, Gary,(and the others too) for the thoughts and the heap of information. It will take me a while to digest it all. Re your last paragraph: entirely my sentiment, and to make it worse, someone had slipped a B20 block with a C cam under the E head! A real hot combination with the BW35. ;-( I bought it as a winter beater to keep my "93 240 Classic SW and my 544 out of the winter salt, but, of course, I had to keep messing with it. So now, with the M41, a D cam, IPD bars, and progressive rate springs, it's turning into rather a fun car to drive.
Bob S.
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Gary,
The BW35 went to the scrap heap without my pulling the speedo drive gear, but if, as you concluded, it was interchangeable with the M40's gears, it wouldn't have fit. The M41 pinions have a much longer shaft and larger gear. Knowing the number of teeth could have been of some help. From the data you supplied, I would guess that it was the one with 16. BTW, when I asked my UK supplier if by any chance there was a 22 teeth gear availble, (I was thinking of my M41 equipped PV who's speedo is 10% optimistic.) he replied that no, they weren't because they had only been used in Volvos and the shaft was too long. This reply makes me doubt that the 17 teeth gear he offered me would fit the M41. I asked him the pertinent questions and hope to hear from him tomorrow.
Bob S.
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I went out to the garage and checked all the M410 speedo gears I could
get my hands on.
I found:
Black -- 20 teeth
Green -- 21 teeth
Blue -- 18 teeth.
I didn't pull any from M41s or the 164 that is in operation now.
If I do, I'll check them out too. I can tell you that the speedo
in the 122 wagon read about 20% faster than life - I think that
M41 came from a 1975 240. It has the 4.56 gears. So maybe the
gear would be right for a 3:73 diff which would be 18 teeth for a 164.
When I get it out I will probably put in a different one.
--
George Downs Bartlesville, Heart of the USA!
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Good to hear from you, Gary.
I guess that all the units that used the J-type overdrive could interchange
gears. This would include at least the M410, which had 3.54 or 3.73 ratios
in the rear end. According to my fiches the p/n's are 3.54:380913-4 (17t);
3.73: 380754-2 (18t)
For the M41 my fiches say only one p/n, 380753-4 and I would assume a 4.3
ratio for this. The rear ends shown on this fiche are 4.1, 4.3 and 3.9.
I agree with you that this gear is probably 20 teeth.
Then there are the later trannies that also use the J-type OD.
I know nothing about them.
Looks like maybe a 164 gear for the 3.73 might be fairly close, p/n 380754-2
at 18 teeth. It is definitely wrong for my 164 which has an M410 that I
installed with the 3:31. OD is not worthwhile at less than about 70 mph
in this car!
Maybe I should go out to the garage and look things over in the gear dep't.
Would be nice if the parts fiches showed ALL the info: appropriate rear end
ratio, number of teeth AND COLOR. I have yellow, green and black in a couple
different kinds.
--
George Downs Bartlesville, Heart of the USA!
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George/Sil,
As far as I have observed (very early model 240s with the same speedo as the 73-74 140s) during my rounds at Pull-A-Part, the cars that came with the auto box had the speedometers marked 0,99 and the ones with the stick had the 1,03 ratio. Then again, it could have been coincidence.
On my 74 144 with the m-40, I replace the non functioning speedo (1.03) with one from a 77 244 with the auto tranny (0.99). It is pessimistic by about 5 mph. According to my 74 144 brochure, at 1000rpms in 4th gear, the car should be moving at 19 mph (your gear ratios might differ unless your M-41 came out of a 74). Do the math, and you should come up with the answer, provided you have an accurate tach. My factory tach shows 3000rpms at 50mph, with respect to the 0.99 speedo, (actual speed 55). I found out the error on my 144 few months ago while driving past a speed detector which displays your speed on an overhead signboard as you pass by.
Like George said, try swapping speedo with different ratios around. My guess is that the one with the 1.03..er I mean 1,03 ratio should be "purdy" accurate, given your M-41.
When you are done with the speedo, you might want to start swapping the gas gauge around...
--
...and the bricks keep on rolling
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Thanks for the input guys -- lots of food for thought there. Just to make sure we're in synch on terminology: when I talk about "speedo drive pinion" I mean the gray plastic gear that makes up one molded piece together with the little output shaft that drives the speedo cable at the OD unit.
I think that the speedometer is actually functioning as it should relative to the impulse it is receiving, and that it doesn't need cleaning, lubing or spring adjustment because both the odometer and the speedometer show the same degree of pessimism. The difference between a 0.99 and 1.03 would account for the 5% difference that GT experiences, but can't explain my 20%. Where, BTW, is that marking found on the speedo? [Yes, George, my Venezuelan wife shocks me with commas in our check book where I would use periods. So it's not just the Europeans. But then, I think we're the only country left in the world using feet, inches, gallons, and pounds. I wonder who is right ;-). And I also, after decades of hunting for the right words in Spanish, have become an expert circumlocuter.]
I have no idea of the origin of the M41. I took it out of a car that had also been converted to OD from something else. I'm also not certain of my differentials ratio - no tag on it. Most likely it is 4.1, but it could be 3.91 or 4.3. I can do the crankshaft rotation test, but whatever the reult, it still wouldn't account for more than a 5% discrepancy; but who knows how all the discrepancies can add up?
Meanwhile, I've heard from one outfit in the UK, and they actually have a 17 teeth drive pinion. I may just go for that and see what it does fo me.
Bob S.
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Well, that first paragraph above was definitely BS. I just pulled the gear to take measurements,and it is a black plastic gear on a steel shaft. so much for my memory :-(
Bob S.
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