JD 70D puller

doug62 · Aug 30, 2014

I bought a non running 70D for a senior project for my nephew, he got it running and was so proud of it I gave it to him for graduation present. He took it to a tractor pull a couple of weeks ago and now were both hooked! Anyway can anybody help him figure out how to gear it down so he doesn't power out. Can a creeper gear from another model fit in it? Also how can you increase the fuel to get more power? Any help would be appreciated. Thanks :?

buickanddeere · Aug 31, 2014

Getting custom cut gears is the only way to slow that fast first gear.
Probably simpler to make more power . More ground speed will coast the sled father and over spin holes, soft spots etc.
The three most important factors to a long pull in order of importance is traction, traction and traction.
Does it spin out or power out?
Most 70's have had the cracked factory head replaced with the 720/730 head with the larger intake valve.
The two cylinder isn't like dialling power up on an IH 466 up from tractor rating to highway truck rating.
The usual airflow enhancements are required to burn more fuel.
Dry air filter element. Port match manifolds and ports. Blend rough edges from ports. Three angle valve job. Some folk install 830 intake valves. Re-ground cam. 730 oval muffler. 720/730 13mm pumps and nozzles . New valve springs. 1500rpm.
Max hitch height. Drawbar short enough to lift front wheels but not lifted sky high. Tinker with tire pressure.

doug62 · Sep 1, 2014

(quoted from post at 14:35:02 08/30/14) I bought a non running 70D for a senior project for my nephew, he got it running and was so proud of it I gave it to him for graduation present. He took it to a tractor pull a couple of weeks ago and now were both hooked! Anyway can anybody help him figure out how to gear it down so he doesn't power out. Can a creeper gear from another model fit in it? Also how can you increase the fuel to get more power? Any help would be appreciated. Thanks :?

Yes it powers out way to soon, can the fuel rack be adjusted to give a little more fuel and if so how does one make that adjustment?

buickanddeere · Sep 1, 2014

Put the tractor on a dyno and see what she is making. She maybe down on power and turning up the fuel will only make more smoke.
I've seen worn or rebuilt tractors on the dyno that were way low on power due to mechanical problems or wrong adjustment.
What weight class, what tires and what kind of track?

doug62 · Sep 1, 2014

(quoted from post at 07:15:18 09/01/14)
Put the tractor on a dyno and see what she is making. She maybe down on power and turning up the fuel will only make more smoke.
I've seen worn or rebuilt tractors on the dyno that were way low on power due to mechanical problems or wrong adjustment.
What weight class, what tires and what kind of track?

His weight was 7700 pounds so they put him in 8000 class, he couldn't shed off the 200 pounds to make the 7500 class, he's got the pony motor and rollamatic front end so she's heavy, tires are almost new tread but they are old and hard rubber co - ops 15.5x 38s I think, track was sticky. He had his air pressure if I remember right around 12 psi. Still running oil bath air cleaner, stock drawbar, no added weights

doug62 · Sep 1, 2014

Also running straight pipe exhaust

buickanddeere · Sep 1, 2014

She should pull that. The engine making less than rated power is suspect.

JD 70D puller

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