7745 clunks when making turns

[david_lindsay]

My 1988 7745 clunks/jerks when turning. Other than that it is a good tractor that I use very little, usually just for moving snow in the winter. I believe I read somewhere in this forum that the the gears/brakes load up and it has to be driven reversed to unwind it. Any ideas? Also I see pics of the 7745 in John Deere colors as their 2400 series. Fox

 

[bigdoug]

I have some questions. Does the 'clunk/jerk' happen all the time or only when turning on pavement? How sharp is the turn?

Without more information to go on, it sound like the tractor is in 4WD. Have you tried to put in in 2WD?

 

[david_lindsay]

Big Doug; Thx for info. It was in 4WD low range on open field. I tried it in 4WD high range and awhile the field is wet today very little lockup/clunk. I tried it in 2WD and no problem. Why in 4WD low especially. THX Fox

 

[bigdoug]

I don't know the technical reason why 4WD Low Range clunks, but my pickup truck does the same thing in 4WD Low Range. I think it's pretty common.

 

[grumpy]

transmission wind up and jd owned part of zetor for awhile.they sold jd badged zetors in various country's around the world.

 

[Renze]

transmission wind up and jd owned part of zetor for awhile.they sold jd badged zetors in various country's around the world.

The Zetor/JD cooperation was in the time that Zetor was still state owned: JD never owned part of Zetor. HTC bought it from the Czech state and a national bank.

 

[grumpy]

transmission wind up and jd owned part of zetor for awhile.they sold jd badged zetors in various country's around the world.

The Zetor/JD cooperation was in the time that Zetor was still state owned: JD never owned part of Zetor. HTC bought it from the Czech state and a national bank.

you sure i reckon many folk would say the jd /zetor cooperation,anyroad one thing for sure the quality control of zetors was vastly improved at the time.

 

[alan]

Some of the 7745's had a limited slip diff in the front axle, sometimes giving the symptoms you describe

 

[grumpy]

Some of the 7745's had a limited slip diff in the front axle, sometimes giving the symptoms you describe

thought only the carraro axles had an lsd?

 

[Renze]

Some of the 7745's had a limited slip diff in the front axle, sometimes giving the symptoms you describe

thought only the carraro axles had an lsd?

You had three options: open, no-spin and true-trac. I think no-spin is a Getrag trademark.

 

[ricc]

transmission wind up is a bit complex....
if you take an old landrover with equal size wheels going in a straight line both axles are turning at the same rpm and travel the same distance, if one axles tyres are slightly more worn , or different pressure and bulge more , the wheels have to turn at differnt rpm to cover the same distance... not possible, (unless you have a centre diff like on a later landrover) or something has to break... given perfect tyre grip it would be a propshaft joint or cv in the front axle, in practise when the strain in the drive train builds up the wheels slip a bit on the ground to release the stress...any wear in the joints produces the audible clunk as it unloads. thats why you should only use 4wd when conditions are such that the tyres can slip.easily.. not on dry tarmac.or concrete

later coil sprung landies with permenant 4wd have a centre diff so they can drive on road... some have a difflock on the centre diff to lock it for mud.

with tractors with different size wheels the gear ratio of the front and back diffs has to be different so the different sized wheels doing different rpm actually cover the ground at the same feet per second (approximatly , in practise all the tyres will actually be slipping but at different rates)

when turning the inside wheels travel less far than the outside ones... the axle diffs take care of that... but the rear axle usually cuts the corner a bit so travels less far than the front one... again tyres have to slip to take up the differance. or you get wind up .

hope that removes some of the mystery

 

[grumpy]

what mystery the more you turn the more load builds up in the transmission that has to get released at some point usually when you engage 2wd drive as the strain has been relieved.then clunk.

 

[crankshaft]

Some of the 7745's had a limited slip diff in the front axle, sometimes giving the symptoms you describe

Exact . Its normal for a Carraro Its has a ratchet inside the differential that relase the pressure when you turn.
My 7245 clunk very hard in forrest job .but the traction is superior with this system than the John D .