Lowering a JD 2640

[NuttyFarmer1970]

I am looking at purchasing a 1978 JD 2640 but it has 15.5-38s on the rear and I want to run a much smaller diameter tire because I'm using it in an orchard. I don't know much about changing wheel sizes, but it looks like the tractor just has a rear axle with a grove for a key and some sort of pinching mechanism in the wheel.

How small can I run on the rear end? I'll attach a pic. Is there a name for this kind of wheel and can I get wheels and tires to interchange?

Also, if I drop the rear end, is there an easy way to alter the front so the tractor isn't just tilted to the rear?

 

[NuttyFarmer1970]

 

[centash]

That's a rack and pinion axle. You can probably find a 30 or 28 inch cast centre
that will match up to the axle and a set of low profile tires on 14 inch implement
rims for the front....won't be cheap though...and then you will need the exhaust
manifold for an underslung muffler, or just use an elbow and lay the existing
muffler flat.

Ben

 

[Tx Jim]

I think 28'' rear wheels is the smallest JD offered that were designed for rack & pinion axles.

 

[NuttyFarmer1970]

Is there a specific diameter on the axle, or are they standard? I tried searching a 14.9-28 rack and pinion style wheel/tire combo, but I'm not sure where to look.

Also, If I find a pair, I will have dropped the rear 10 inches. Is there an easy way to drop the front end?

 

[Tx Jim]

28'' rear wheels were offered for 2640. Wedges that fit 2640 axles fit 46 different JD tractor models

 

[Tx Jim]

It appears from viewing parts schematics that JD 2640 frt axle could have 3 different height of steering knuckles/knees

 

[centash]

Well, going from a 38 to 28 will only lower the rear about 5 inches...Plus whatever change in tire profile you can get.

Ben

 

[Resting Relics 1]

A pretty expensive endeavor to change to 28-inch unless you can find someone who wants to swap. A lot of those tractors came with 28-inch tires. Might be cheaper to look for one with the size rubber you want. Good Luck!
John

 

[tomstractorsandtoys]

You have the 36 inch centers that take the 38 inch rims with the drop centers. Those rims are only available from Deere and very expensive. Customer had his 2630 here for a paint job but wanted new tires first. Found both of his rims bad. I sold him 38 inch centers off a 2510 (F1500R centers)and he bought two new rims and was still several hundred cheaper than Deere.Tom

 

[D-]

All that work and expense and you still have a 2640.
Common to have balancer shaft bushing fails ruining
the block. Depending upon model also have hi-lo failures.

 

[Tx Jim]

(quoted from post at 10:04:56 02/27/20) All that work and expense and you still have a 2640.
Common to have balancer shaft bushing fails ruining
the block. Depending upon model also have hi-lo failures.

I'm curious do JD 4 cyl engine balancer shaft brgs/bushings fail more frequently than other brands of farm tractor balancer brgs/bushings?

I don't remember any balancer shaft failures when I was employed at JD dealer BUT those same engines have a lot more hrs of use today than way back then.

I'm not advocating modifying the 2640 as mentioned by NuttyFarmer1970 because I think it will be cost prohibitive.

 

[D-]

The 26s were notorious about spinning bearings.
They were so out of balance they had extra weights
bolted to the shafts. Back in the day every dealer
around here had those blocks laying in their scrap
pile.
There was a jockey around here that brought 26s in
from Illinois. All had papers to prove the engine
had been replaced.
That's the reason they went away from that engine.
(2750 had smaller turboed engine).
The problem was rpms. Industrial tractors didn't
have the problem. 6000 series went back to that
engine at lower rpms.
As far as other brands go I think Ford used a balancer
box similar to a 3020. I'm not sure about other brands.
Even before 26s there was a problem. If you remember
there was one part number for a shaft.... fit either
side. Then Deere started grinding a RH shaft opposite
than a LH. Thought the "grain" might have something to do with
wear.
Around here 26s are considered the 2010 of that generation.

 

[Tx Jim]

D-
After reading your reply I remembered JD dealer where I was employed for some unknown reason didn't sell very many if any new 2640's.
Thanks for your reply,Jim