I have the 727, 3.07 combo, and was wondering what rpms would i be turning going from that combo to an auto overdrive tranny with 3.54/3.73 or 4.10 gears. Will I actually be able to drop the rpm at highway speeds changing the config? I want to be able to roll heavy loads without mashing the go petal. But will also like the lower rpm at highway speeds.

 

Put the o/d trans in front of the 3.07 rear and that'd be sweet.

Remember though, your not getting a true .69 o/d ratio with the 518 or even a true 1:1 with your 727 because they're non lockup trans, converter slippage.

theres alot of online calculators to figure this stuff out.

a 518/4.10 truck is going to be worse then a 727/3.07 truck.

a 518/3.54 truck will be slightly better then a 727/3.07 truck..

I bet a 518 with a Good torque converter along with 3.07's would be sweeeet.

 

What i am looking for is to be running about the same rpms or less as the 3.07 with an o/d tranny with lower gears. This is a plow truck and I want to be able to push my 10 foot plow with a full load of snow at 3am without making "too" much noise in my residential areas. I do not like going into low range !This truck is straight piped. Going to 4 inch this summer.

 

snowjoker, i have a 2wd truck but i just started the process of building a 518 to replace my 727 and i as well have 3.07 gears. i dont know my current RPM but when its done ill let ya know what i think!!

 

If you put in a 4 speed auto and want the truck to work then go with the 4.10's Plowing snow is hard on trannys so the lower the gear the better. 4.10's with the overdrive has about the same final ratio as the 3.07's with the 727.

 

I was thinkin if I went with the 3.73 I might be able to gain some mpg along with having some more grunt while plowing.. It will be a toss up because I push my trucks hard while plowing... I'll run that truck fully loaded with all its winter gear at near 10,000 pounds...

 

I always ran my 89 727 in low range plowing. The truck was still very fast in reverse and 1st low was not very slow either.

 

I know this is an old thread but I have some questions regarding my axles.. To my understanding this non IC truck has a d61/d70 axles ? I do want to get lower gears like 3:54 or 4:10 Will the axles them selves have to be replaced or will the carriers in them support the different ratios ? Ive been looking at ring and pinions on eBay. I have been searching but appears to be that these axles wont support other ratios ? is that correct? or will I end up having to get something out of a donor truck for axles maybe d60s ?

 

You need to replace the axles. The housing is different on the 3:07's.

I bet if you check around some you could find someone wanting a matched pair of 3:07 axle that has 3:54's or 4:10.

BTW 60 MPH with 3:07's and a 518 auto =1650 RPM.

 

Problem is the rear pinion is chipped up pretty good, on one tooth and a couple others have small chips on them, but its still going. I am not sure how much they will take...

 

The SRW 3:07 rear axles are easyer to find that a dually rear. They show up for sale every once in a while.

How much they can take depends on how much backlash the axle has. If it is loose from worn bearings and age. It could grenage about any time. Plowing snow is hard on axles and Tcases.