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140 rear same as 240?

chirish1234

chirish1234

Active member
Joined
Jan 2, 2009
Location
NJ, US
Ok. I plan on having smaller tires on the car. The factory is 165R15....which is a very tall tire. I plan on having 225/50/16 which is close but still smaller. I believe the rear in it now is a 4.10? I want a 3.73 or similair. That would increase my top end, correct? I just want to know if the dif's swap or if I have to swap the whole rear end.

The car is a 1971 144S with an M40 soon to be M41(overdrive). Also the car speedo when it says 70 im doing 60....so its pretty bad.

Thanks!
-Nick
 
It's a 1030 1970 and up.
Your best bet would be swapping in a whole rear end from a 71-74 164.
Fakey edit;
You'll need some more HP to push the taller gears.
The engineers didn't make many mistakes when they figured this stuff out.
 
Axle housing is different. I'm not sure when the diff/axle internals changed. I know some years of 140 used the Dana 30 27-spline but I'm not sure what else was used in the early days. If it's a Dana 30, you need to find a ring & pinion from a 1030 axle if you're looking to swap in 240 parts. Or find a complete rear end. maybe Lawrence has one (aka fidel).
 
....and you're probably aware, if you go to an even shorter tire, it's going to make your speedo inaccuracy even worse than it already is.
 
IIRC the stock rims on the various '72 to '74 140s I had were all 15 inches, so if you're running a smaller overall rim/tire diameter it will throw out your speedo readings. See if you can get the stock wheel/tire specs (my ancient memory couldn't find them) and then go here for rim/tire resizing comparison: http://www.1010tires.com/tech.asp
 
Nick, if you want to try some stock rims and tires to see if that makes any kind of difference in your speedo, you're most welcome to come buy and swap a set for giggles. You could swap a speedo too if you want. IMHO, you may want to retain the 4:10 rear end. You'll get off the line faster, or rather comparitively faster than going with a lower ratio. My car was originally an autotragic and I believe the diff ratio is 3.31. It's a dog off the line. I plan to swap in a 4.10 rear end this summer.
 
goldbrixx said:
Nick, if you want to try some stock rims and tires to see if that makes any kind of difference in your speedo, you're most welcome to come buy and swap a set for giggles. You could swap a speedo too if you want. IMHO, you may want to retain the 4:10 rear end. You'll get off the line faster, or rather comparitively faster than going with a lower ratio. My car was originally an autotragic and I believe the diff ratio is 3.31. It's a dog off the line. I plan to swap in a 4.10 rear end this summer.
Click to expand...

391's on AT 1800E's but I think 140's were geared alike auto or manual.

71 142's & 144's had 410's & the 145 still had the 430's from the earlier cars.
 
Last edited:
goldbrixx said:
Nick, if you want to try some stock rims and tires to see if that makes any kind of difference in your speedo, you're most welcome to come buy and swap a set for giggles. You could swap a speedo too if you want. IMHO, you may want to retain the 4:10 rear end. You'll get off the line faster, or rather comparitively faster than going with a lower ratio. My car was originally an autotragic and I believe the diff ratio is 3.31. It's a dog off the line. I plan to swap in a 4.10 rear end this summer.
Click to expand...
Ill trade rears with ya lol. I have a much shorter tire which should make up for being a dog off the line.
Redwood Chair said:
:doh:
Going from 25.4" to 24.19" is going to do that not to mention the 3% margin of error originally built into the system.

You're trying to fix a nonexistent problem of your own making.
Click to expand...
I knew I made the problem. I want to run a 225/45/16 so I need the 3.31 to make up for the short tire. That's my goal. Also how low the car is its going to his the inner front wheel well with a stock size tire.
 
chirish1234 said:
I knew I made the problem. I want to run a 225/45/16 so I need the 3.31 to make up for the short tire. That's my goal. Also how low the car is its going to his the inner front wheel well with a stock size tire.
Click to expand...

Gear sets for 1030's are readily available and cheap new for 1030's unlike 1031's.

Like I said earlier an axle swap from a 164 is your best bet unless you have connections to get the gears swapped.
 
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