riotwarrior
Full Access Member
Wait so all superduty s42's have the diesel gears?
Nope not same depends on engine
DIESEL S42 have diesel gears
GASSER S42 for 460 are different spread as shown above
Wait so all superduty s42's have the diesel gears?
Nope not same depends on engine
DIESEL S42 have diesel gears
GASSER S42 for 460 are different spread as shown above
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.for myself i would like the wide ratio better and the overdrive ratios are so close i doubt there would be a difference when driving, and the s547 has a stronger input shaft and the s542, its not the gearing they are just different thats all, and you could just switch cases to get the ratio you want and so it will bolt up to the engine without modifying, i know its not a simple task but its an option
I was running a 42 with about 500 ft/lbs to it. Research our big block cousins with zf's. lots of them are running more than they are rated for. One puller around here, the "Morewood Express", runs one and its 500 some cubes. So the strength isn't a huge concern with an IDI IMHO
Doesn't mean the S42 isn't a good trans, just be careful comparing apples & oranges.

Real easy solution for you - the ratios are printed on the side plate on the trans. Just read what it says on there.
I would run the S47 as long as it looks like it's in decent shape. Maybe see if you can get it inspected by a trans shop?
I've run both a S42 & S47 in my rig (lucked into what seems to be a factory reman S47) and the lower gearing on the S47 is definitely nice if you do any real towing or such. On the other hand, the gaps between gears are a bit bigger and more noticeable. I plan to fix this by running a US Gear splitter eventually, but that's down the road a bit.
For me having the little bit of added strength from the S47 add some peace of mind. Why not if you can?
I'd also note that a gasser race/pull rig is going to put somewhat different stresses on the trans than a high torque heavy towing rig. A 500 hp gasser is probably making about half the torque at double or more the rpm that a turbo idi would run..... and it's going to be very intermittent high stress with a short duration. Little bit different than slogging up a steep grade with a heavy load and that diesel lugged down to 2000 rpm.....
Doesn't mean the S42 isn't a good trans, just be careful comparing apples & oranges.