Does a John Deere 6400 have to crank fast enough to star

Helping a neighbor today with his John Deere 6400. His battery is going on about 8 years now and he wants to replace it thinking that it is about at the end of its life and he doesn't want to have problems 6 miles from his home base. Always has been pretty hard to start in the winter without jumping it. His current battery (group 31) which is not to original tractor specs has about 1000 cranking amps. He was told that the tractor requires a special battery with around 1200 cranking amps in order to get it to spin fast enough to start. Just was wondering if that was to build the required compression or is it something to do with oil pressure or the injection pump. Went to a farm store selling Interstate and Deka batteries today and the owner of the store sort of verified the fact that the 6400/6420 required a special battery as his two sons each had a Deere 6420. Sounds like his sons put cheaper 950 cranking amp batteries in their tractors and keep them inside in the winter. Store owner said Mother Deere possibly has a $300 price tag on that specific battery. Maybe the bigger battery is recommended because it is just a single battery setup. Thanks for your thoughts.

They sure start better with plenty of battery.

These slow cranking 6400's have been discussed on Newagtalk. The consensus seems to be switching to a gear reduction starter will improve cold cranking somewhat:

https://talk.newagtalk.com/forums/thread-view.asp?tid=688901&DisplayType=flat&setCookie=1

My 6400 cranks slow when the weather is cooler but I keep it in my heated shop in winter. Otherwise I'd try a different starter.

700A is highest capacity battery I located in 6400 parts catalog
12V, 154AH, 700A, NLA; ORDER AL203839, MARKED AL119622, SUB FOR L101313

I agree highest cranking amp battery is normally the best especially when experiencing cold ambient temps.

I buy the largest CCA battery that will fit. Tractor isn't any good to me if it doesn't start when cold.

I had a 4230 with a 6v battery on both sides. I wasn't happy with the starting performance. One problem was that the current loop was from a main engine casting mounting bolt, you connected ground on the right side through the right battery out of that battery to the left battery and out that to the starter solenoid. Then the starter's case was bolted to the engine frame....meaning part of the loop was from the starter's case through that interface with the engine block, out and out the other side of the block as mentioned.......and the connecting wire was 0 AWG.....for the record, 0 is used for entrance electrical service rated at 100 Amperes or less......way less than the 300 Amperes, give or take needed to start a 400 cu. inch diesel engine.

So, I put a 12v battery on each side, wired them in parallel with 00 AWG cable (yes I routed 2 cables under the floor pan connecting both sides of the tractor) and put the ground wire under one of the starter mounting bolts, with the terminal touching the starter's case under that mounting bolt.

Lastly the batteries were 31 series (3/8 studs) I get at the local OTR truck dealer (they buy them by the pallet load for a super price), sealed, 925 CCA.......and they custom made the cables for me too.

The difference......I didn't have to start it.....I just had to think to myself.....START and if a flash it was up and running.....more or less.