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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 27754
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I'm changing the drive belt on a Deere STX38, and I'm having

Customer Question

I'm changing the drive belt on a John Deere STX38, and I'm having a LOT of problems. Clearly, I'm missing something somewhere...
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: All day.
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: No
Submitted: 9 months ago.
Category: Small Engine
Expert:  Curtis B. replied 9 months ago.

Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!

Expert:  Curtis B. replied 9 months ago.

Geared transmission or hydrostat? Where is the problem? Do you have the brake/clutch locked down to loosen the belt?

Expert:  Curtis B. replied 9 months ago.

Here is hydrostat instruction above.

Customer: replied 9 months ago.
I'm gonna try again here, Curtis. Am I talking to a person or an automated response?
Expert:  Curtis B. replied 9 months ago.

I'm real! Did you see the link, there is also instruction for the geared transmission.

Customer: replied 9 months ago.
Hey good! Sorry for all that, but JustAnswer tends to send a BUNCH of auto messages. OK... Yes, I saw the link you provided, but it's not applicable. I have a John Deere STX38. It has two belts; one on the deck that drives the blade pulleys, and one from a PTO on the shaft from the engine to the deck. I'm changing this second belt. I've confirmed I've got the right belt, and I've followed the instructions in the manual, but the belt will NOT go over the pulley off the engine shaft (the PTO pulley) with the deck locked in place as directed by the instructions. If I slip the belt on first, the deck will NOT line up to lock into place.I'm sure there's a way to relieve the tension on the belt when doing the installation. The manual refers to such a "tension lever", but I can't seem to find it on my mower deck. (The mower is several years old, and I'm concerned someone in the past may have "modified" the deck for some reason, eliminating the lever. Or, the picture shown in the manual is not representative of my mower. Or... well' that's where you come in.)
Customer: replied 9 months ago.
I can send you pictures as needed so you know exactly what I am looking at, and advise from there. Just let me know what you need to see...
Customer: replied 9 months ago.
My fault... I should have said a John Deere STX38 YELLOW deck, as opposed to the "Black" deck.
Expert:  Curtis B. replied 9 months ago.

You want the mower drive belts, not the transmission belts!

Expert:  Curtis B. replied 9 months ago.

You do have the standard 38 inch deck? only decks that I ever saw with the tension lever is larger 54 inch decks.

Customer: replied 9 months ago.
Yeah... That's part of my confusion. Yes, it's a standard 38" deck. The STX38 only came with a 38" yellow (and then later, black) deck. BUT, the manual for the JD STX38 identifies a tension lever to be moved in replacing the belt, and I cannot find any such lever on my deck. (https://jdagccc.custhelp.com/ci/fattach/get/51677/0/filename/686+-+STX30+and+STX38+Mower+Drive+Belt+(SN+100001+-+).pdf) See page 3, step 5 (to relieve tension), and page 5, step 12 (to resume tension)What am I missing here? Do you want pics of my deck? (Maybe you can find it... :) )
Expert:  Curtis B. replied 9 months ago.

I just read the link you sent. You have the deck spindle belt in and are just trying to remount the deck. If you mount deck and leave the belt off the engine pulley, how close can you get the belt? The typical mower drive belt you install deck, then slip belt over the drive and driven pulley, the with it on the two main pulleys , then slip the belt on to the idlers! ??? Deck has two adjustment holes to change the front location. that will let you move deck forward toward engine pulley .

Customer: replied 9 months ago.
34;You have the deck spindle belt in and are just trying to remount the deck." - Correct, but when I get the deck remounted, I don't have enough slack to get belt over the engine pulley."If you mount deck and leave the belt off the engine pulley, how close can you get the belt?" - I assume you mean onto the engine pulley, and the answer is not really even close. (I mean, it appears the belt WILL fit, if I can get it onto the pulley... but I don't have enough slack. That's why I think the "tension lever" is key. But I can't find it."The typical mower drive belt you install deck, then slip belt over the drive and driven pulley, the with it on the two main pulleys , then slip the belt on to the idlers! ???" - OK... I have the belt on the deck sheave, and I can either attach the deck at all four corners (Front, Back, Left and Right), and be unable to get the belt onto the engine pulley, OR I can slip the belt onto the engine pulley, but then it is too far forward to attach at the rear corners."Deck has two adjustment holes to change the front location. that will let you move deck forward toward engine pulley." - No. Once attached at the rear, there is no forward or backward movement possible. It's a fixed distance between the rear attachments and the front attachments. (I don't know why the manual calls attention to the "two" holes.... only one set will fit the forward arms...)
Expert:  Curtis B. replied 9 months ago.

And belt measures same as old belt?

Customer: replied 9 months ago.
The rear attachments slope down and forward. If I set the deck on 1" boards, the deck slides BACK... away from the engine pulley.
Expert:  Curtis B. replied 9 months ago.

Belt exactly same as old belt?

Customer: replied 9 months ago.
Can't tell, but it's pretty close. Real, real close. Old belt wasn't broken, but very worn. Within "it might just have stretched a bit" tolerances. And I double-checked with the local John Deere dealer (where I bought the new belt), as well as their on-line parts supply catalog. The new belt is the right one.The new belt will "fit" perfect... if I can figure out how to get it on the engine pulley.
Expert:  Curtis B. replied 9 months ago.

Put belt on the pulley, and use a come a long to pull deck back to pin it! Might have to tie front of mower from rolling!

Customer: replied 9 months ago.
OK... That's a really BAD idea... for a couple of reasons. I'm not ready to use a "come-along" just yet. Or a BFH. (Believe me, though, I have considered it!)I have no doubt you know your stuff cold as far as engine mechanics, and I'm pretty sure if you were here we could figure this b**** out. But, as it stands, I think maybe you're at the same place I am with this one. I'm going to ask to speak to another expert... Hopefully someone who's more familiar with this mower model than you or me.Thanks for your time, and taking a shot.Do you pass my question on to another expert, or do I need to contact JustAnswer?Again, don't take this as "dissatisfaction", but I think maybe we're out of your field of expertise.
Customer: replied 9 months ago.
There has got to be a way to shift the sheave on the deck forward enough to slip the belt onto the engine pulley, and then back enough to provide adequate tension in the belt to TURN the deck drive pulley.I just don't know... or can't see... or both, really... how to do that.
Expert:  Curtis B. replied 9 months ago.

All decks I ever saw with a tension lever, has a lever with a clip on the deck, that you slip lever up to release, get belt in place then pull on the lever and let it hang in the deck clip. I don't see a release lever on the parts list.

Expert:  Curtis B. replied 9 months ago.

Is there a square hole in the idler lever, where you can attach a breaker bar, and use it as a lever?

Customer: replied 9 months ago.
34;Is there a square hole in the idler lever, where you can attach a breaker bar, and use it as a lever?" - No. I know what kind of "linkage"(?) you're describing, and it isn't applicable here.About an hour ago, a friend of mine stopped by. She was with a young man. Because the mower is in the driveway, he asked me "What's up?". I told him the problem. In about two minutes, he said "Loosen this bolt here. See if that does anything." I did, and the whole sheave slid forward!He said he thought there USED to be a lever that moved the sheave, but it isn't there now, and PROBABLY some past owner had just devised some kind of bar with a hook or something to move the sheave, and then just re-tightened the bolt, holding everything in place. He said I should check for a spring that would have attached to the sheave to keep tension on it. I looked at some schematics and parts lists, and sure enough there is supposed to be a spring pulling the (missing) lever!So... I've got the deck re-installed WITH the belt on the drive pulley, and the bolt tightened down enough to hold until I can have another friend weld me a replacement lever.Thanks anyway, Curtis. Again, I don't doubt your expertise in engine mechanics and I'd feel comfortable working with you again in the future, BUT your suggestion of "hook up a come along" really didn't fix the problem...I'm sorry I seem to have wasted your time and mine. Good luck in the future!Mike
Expert:  Curtis B. replied 9 months ago.

Good job! That's what we do. Sometimes we get it right.