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M50D-R1 ratio question


jimmy1979

Well-Known Member
U.S. Military - Active
Joined
May 27, 2010
Messages
57
City
Fort Lewis, WA
Vehicle Year
1991
Transmission
Manual
According to the tech articles, the M50D-R1 for a 4.0 has different ratios than other engine sizes. If I put one from a 3.0 behind my 4.0, what will the effect of the different ratios be? How will it affect perfomance?

I am looking for a new transmission because mine pops out of 5th. I just did a clutch job hoping it would fix it but, no dice. That and the fact that I found a large piece of steel on the drain plug magnet. I guess I'm just getting ready for a catastrophic failure.
 
4.0l transmissions have lower first gear ratio. so using a differant transmission will affect off the line performance and towing power.

im not sure if any other gears use different gear ratios or if its a direct bolt in swap
 
You cant just stick a transmission from a 3.0 behind a 4.0. The bellhousings are different and integral with the case, and would require you to transplant the gears from one to the other. There is no point in doing that. Your better off having a transmission specialist diagnose the problem.
 
I didn't know that about the bell housings. I found used transmissions between 250 an 400 bucks. I can get a rebuild kit for way cheaper than that. How hard would it be for a novice to rebuild a manual transmission?
 
According to the tech articles, the M50D-R1 for a 4.0 has different ratios than other engine sizes. If I put one from a 3.0 behind my 4.0, what will the effect of the different ratios be? How will it affect perfomance?
You cannot use a 3.0 tranny behind a 4.0, the bellhousings are different. You can use a 2.9 tranny. The first 3 gears would be lower, giving you more torque to the ground but you will redline a little sooner in each gear.
4.0l transmissions have lower first gear ratio. so using a differant transmission will affect off the line performance and towing power.

im not sure if any other gears use different gear ratios or if its a direct bolt in swap
4.0 M5ODs have higher 1st-3rd ratios.
 
You cannot use a 3.0 tranny behind a 4.0, the bellhousings are different. You can use a 2.9 tranny. The first 3 gears would be lower, giving you more torque to the ground but you will redline a little sooner in each gear.

4.0 M5ODs have higher 1st-3rd ratios.

not according to the tech library. a numerically higher number but a lower ratio

edit: i double checked you are right, the layout threw me off
 
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I didn't know that about the bell housings. I found used transmissions between 250 an 400 bucks. I can get a rebuild kit for way cheaper than that. How hard would it be for a novice to rebuild a manual transmission?

$250 bucks for a good used one is a small price to pay to avoid the frustration of tearing one apart. Not to mention the parts can be very expensive if you find a gear or some other major component damaged in there. Manual trannies can be a pain in the ass to tear apart and get back together if you don't have any experience. I personally hate 'em!! I wouldn't rebuild one if I could get a good one for $250.
 
The only problem I have with buying a used one is that its used. I have no way of knowing if it is good until I put some miles on it. That being said, there are some wrecking yards that are offering a 30-60 day warranty. In my limited experience dealing with the wrecking yard around heres is that even though they offer the warranty, they don't like to honor it and, when they do, it is usually a major PITA.

I have been hearing a lot about how much of a PITA a rebuild can be.
So, now which one.....?
1. guessing game if a used one is good or not
2. a$$ pain of a diy rebuild
 
Usually you can tell something about the condition of a used tranny by popping the top cover off and inspecting the gears, synchronizers, etc. for pitting, chipped/rounded teeth, etc. and that there isn't a bunch of metal in it (obviously if it doesn't turn nice & smoothly and/or has a ton of side-side play on the input shaft (more than a few mm), you shouldn't even bring it home from the yard).

Then get a feeler gauge and check the clearance between the synchros with the minimums listed in the Ford shop manual.
If they're well above the minimums, then I'd say it should be a fairly safe bet.
 
Usually you can tell something about the condition of a used tranny by popping the top cover off and inspecting the gears, synchronizers, etc. for pitting, chipped/rounded teeth, etc. and that there isn't a bunch of metal in it (obviously if it doesn't turn nice & smoothly and/or has a ton of side-side play on the input shaft (more than a few mm), you shouldn't even bring it home from the yard).

Then get a feeler gauge and check the clearance between the synchros with the minimums listed in the Ford shop manual.
If they're well above the minimums, then I'd say it should be a fairly safe bet.

Guess I should have done that with mine while it was out for a clutch. I know something in there is chipped or broken, I found a pretty good sized piece of metal on the drain plug magnet.

Where would I find a Ford Shop Manual?
 
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Ebay would probably be your best bet for a set of factory manuals (I picked up a full set of '90 manuals in decent shape for $40 I think it was).
 

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