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'78 GT18 seems slow. Normal?


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#1 wahoowad OFFLINE  

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Posted February 01, 2015 - 09:32 AM

I finally got my new-to-me '78 GT18 running after a carb and intake manifold rebuild, grease the starter shaft and replaced transaxle fluid. The big Onan twin starts easy and runs pretty good. But when I drive it around the yard in hi-2 and hi-3 it feels like it is moving like lo-2 and lo-3 in my 69 Custom. I would think they move the more or less the same since they both have the 8-speed hi/lo transaxle. They are direct gear drive, right?

 

But for all I know they could be geared much slower? It seems to move slow like the '67 Gravely I had for awhile.

 

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#2 MH81 ONLINE  

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Posted February 01, 2015 - 09:40 AM

My 19.9 will just about toss you off the seat if you let the clutch up fast.
Is there a difference between 3h and 3l?

#3 glgrumpy ONLINE  

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Posted February 01, 2015 - 12:52 PM

If someone has had the axle out or the range lever, it is easy to have the rod back to axle not fall back into the slot on lever at axle. You move the lever and linkage, but not the lever on the axle. Might look under the body, it is tight spot to see, need a good light.


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#4 wahoowad OFFLINE  

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Posted February 01, 2015 - 05:46 PM

My 19.9 will just about toss you off the seat if you let the clutch up fast.
Is there a difference between 3h and 3l?

 

Yes, there is a noticable difference. 3-hi is "ok" speed-wise but more like 2-hi on my little Custom.

 

Grummpy - not sure what you are suggesting? I am able to move through the different gears and feel a different resulting speed.



#5 KennyP ONLINE  

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Posted February 01, 2015 - 05:57 PM

Is there a possibility one of the pulleys for the drive belt has been changed? If the engine pulley is a size smaller, I think it would slow the speed!


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#6 MH81 ONLINE  

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Posted February 01, 2015 - 08:05 PM

I know the drive pulley on the tranny is pretty big on these.
If the tranny was changed for another unit, it is possible they didnt transfer the big pulley.
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#7 wahoowad OFFLINE  

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Posted February 01, 2015 - 09:53 PM

Yes, the tractor drives as if a pulley is smaller....I was actually thinking of using that description earlier. Everything feels like it is working other than the speed seems slower. But I looked at the engine pulley and it looks the same as I see on pics of other GT/18s. How can I tell by looking at the trans pulley? I recall it was big. 

 

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#8 KennyP ONLINE  

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Posted February 02, 2015 - 06:14 AM

If the driven pulley (tranny) is larger than original, you will then get a slower speed, also, as it will take more revolutions of the drive pulley (engine) to make a full revolution at the tranny. I hope someone can get measurements from their tractor pulleys for you to check yours..



#9 TAHOE ONLINE  

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Posted February 02, 2015 - 09:48 AM

Yea, that looks like the stock engine drive pulley.

It could be that your linkage is not working properly and you are not engaging in Hi or possbily the drive belt needs replaced, it could be slipping enough to slow tractor.



#10 wahoowad OFFLINE  

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Posted February 02, 2015 - 11:04 AM

I feel both Hi and Lo gears and lever are working as there is a distinct difference when I compare Hi3 and Lo3.

 

I will get underneath tonight and see if I can read the part # off the trans pulley, possibly using a flashlight and mirror. I expect the clearance between the pulley and fender is tight.

 

Will the belt squeal, make noise or burn if it is slipping that much? I haven't noticed anything. The belt has some cracks and the pulleys have a little rust in them but I figure the rust just helped grab the belt :) I don't see any signs of a burning belt and I also see my tension pulley and spring helping hold things firm.



#11 johnwesley OFFLINE  

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Posted February 02, 2015 - 12:04 PM

wahoowad, the engine pulleys are approx. (outside dia.) outer pulley 3", middle pulley for mower deck 5", and inner pulley for tractor drive 41/4". Sorry, can't see back pulley. As I said these are quick measured with tape outside edge to outside edge of pulleys.

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#12 wahoowad OFFLINE  

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Posted February 02, 2015 - 01:11 PM

Thanks for checking! I am hoping to find a part # tonight to confirm I have the right size trans pulley.

 

You guys have me wondering about the belt now. It is intact and working but perhaps it is old and stretched from sitting for a few years? That said, I'm not sure how to confirm if it slipping...?



#13 KennyP ONLINE  

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Posted February 02, 2015 - 01:36 PM

If the belt is slipping, it will clean out the rust! If I looked up the correct tractor, the engine pulley is part # 634A104. Belt is 2692R which converts to NAPA # 5L830W (21/32" X 83"). Trans pulley is part # 6461H2.



#14 TAHOE ONLINE  

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Posted February 02, 2015 - 06:32 PM

The pulley on tranny measures 7 1/2" on the outer lips. That's off a ss18 model.
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#15 wahoowad OFFLINE  

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Posted February 02, 2015 - 08:42 PM

My trans pulley doesn't have a part number on it that I can see. But it looks like the pulleys I see when I search the Internet for the model number 6461H2. I feel pretty confident I have the right one.

So...what else could give it a slow ground speed?




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