I have an a518 with 37" tires and 3.73 gears and I want to run a sm465 trans, what would the new gear ratio be (ring&pinion) to get high gear the same ratio thanks for your input
if these numbers below are wrong, please correct


a518 ( the 3.73 are a bit tall but not bad)

1st is 2.45
2nd is 1.45
3rd is 1.00
4th is .69


sm465

1st is 6.56
2nd is 3.58
3rd is 1.70
4th is 1:0

 

you take what ever ratio you need. say 3r gear on the sm465 and multiply it by the ratio of your ring and pinion. that gives you your final drive ratio.

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looks like a 2.5737 but i dont have time to double check right now. have to get to class.

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so your final drive ratio in 4th right(a518) now is 2.5737. through a set of 3.73s in the rear. if you want to maintain that same ratio you need to match that same final drive ratio of 2.5737. it easy because the sm465 is a direct drive 4th gear. so to achieve the 2.5737 you need a 2.5737 ring a pinion. to figure the math you take 4th gear. (0.69x3.73) so final ratio is 2.5737 in 4th. (1.0x3.73=3.73 in 3rd) etc.

 

The only options i have is 3.54 2.57 sounds like a big jump, some guys use the 727 tranny and i believe that one is 1 to 1 in high gear. (thats probably why dodge changed it) it would probably work but my fuel milage would most likely suffer, I have these parts laying around, and i miss the low gears in 1st and 2nd for pulling my trailer. it will cost about 4500.00 to rebuild my tranny with good parts (a518) and convert it to a lockup. mabey a nv4500 is in the cards thanks for the reply.

 

Would a sm465 last behind a modified cummins? I think the NV4500 is good option. It has a nice low 1st gear too.

Your going to need a few things for a manual conversion to work:

Pedal assembly
Clutch
NV4500 has drive side transfer case (maybe you can just rotate it)
You might even need a transfer case
drive shafts possibly


I think it would end up being cheaper to build up the a518

 

When I did this swap i didn't know about these forums.(which are pricless) but i new i could do it,but i saved all my old stuff just incase,( it was a manuel)the 465 needs the 1 1/2 input shaft upgrade for it to survive. a 6bt to gm kit (p-30 kit) about 700.00 + cummins flywheel. and some driveline work.
as for the nv4500 there are adapters to convert it to the cummins and old case. If i go this rout its close to the cost of the a518 rebuild. I want somthing different I just don,t know what. now 4rth gear(a518 -1to1 -3.73 - 1800rpm is 56mph (gps) same as sm465 in high gear (right) if i put 3.54 ring&pinion in it then the new speed would be what the sm465 would be.?????what is the formula for that one? ( also have these parts lying around and 4hours of work is alot cheaper of a test) 56 mph is toooo slow (its ok with trailer) thanks for the input

 

This is the calculator i use.

Engine RPM Calculator

At 65 MPH 3.54 rear end and 37" tire your looking at 2100 RPM

 

ya, It looks like it wont work, the strange thing is when i bought the truck it had a diesel,sm465, 4.10 gears and 33". now nothing comes out right. thanks for the link

 

im doing the same swap into my 85 chevy, im gonna use the nv4500 bellhousing, adapter plate,clutch and flywheel. Im gonna use the 3.54 dodge axles under my truck and 37 inch tires. everything lines up with the 1 1/2 input shaft. The flywheel needs bored out to accept the 1'' pilot bearing. Its been done a couple times on another forum, i dont know the rules for posting other forum links. It would be sweet to find 89-90 3.07 geared axle, that would be perfect.

 

The lowest gear ratio in a dana -60 that i could find has been a 3.54 this 89-90-axle your talking about is it a dana. some early chevy's had 3.08 but they were a 10 bolt and 12 bolt. too week and light duty for me.

 

The non inter-cooled dodge trucks with the 3 speed auto (727) have 3.07 axle ratios. They are special Dana 60's and 70's, called 61 and 71.