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SD tensioner mod

6K views 20 replies 10 participants last post by  madpogue 
#1 ·
Who has done it? Was it worth it? Any drawbacks?

My belt is chirping....bad. It only has a few thousand miles on it. All the pulleys are in line and every thing is smooth but I figure after 16 years it probably doesn't have the tension it once had.
 
#2 ·
Re: Dual tensioner mod

I had to change my tensioner out at 300,000 miles found the bushing at the bolt was bad not the spring. The tensioner was straight but sticking.
 
#3 ·
Re: Dual tensioner mod



Then why not just get a new tensioner? :confused: Not hard to swap, and not that expensive.
 
#4 ·
#5 ·
Re: Dual tensioner mod

If you do it post how it turns out mine started chirping a few weeks ago.
 
#7 ·
Re: Dual tensioner mod

From what I have read it is suppose to give more consistent pressure on the belt to prevent premature belt wear.






 
#8 ·
Re: Dual tensioner mod

Everything is back together. It corrected the issue, which isn't a surprise but for one thing, it did require much power umph to pull the SD tensioner.

While I had the bracket off I did take the time to check the EBPS tube, which was clean and free flowing.
 
#10 ·
I think that with both pulleys rotating it is just more consistent pressure.

It definitely has more pressure than my 16 year / 128k mile old tensioner but it doesn't have an extreme amount of pressure. I was still able to pull it back with my weaker arm while sliding the belt on using a short breaker bar.

There was no real cost difference between the SD and the OBS tensioner.
 
#11 ·
The PO of my truck installed one and I like it better and think PsRumors it right. Plus it's easier to install/remove the belt now iirc.

jrc
 
#12 ·
I just replaced the tensioner on mine. The one the parts store gave me was a Gates brand, and was an "upgraded design" with a longer arm. The paperwork inside the box said they did this for extra leverage to improve belt tension consistency. Seems like it works good, easier than changing to a super duty style too... and uses the same length belt.
 
#13 ·
Changing to the SD style was rather easy and it allowed for easy access to the EBPS tube which should be checked / cleaned at some point in the trucks life.
 
#14 ·
The only thing bad about installing the SD tensioner is that once in a while you run across a JK8-1227 Motorcraft belt that's a wee bit shorter than usual. When this conversion was popular, several guys ran across short ones. Got a short Motorcraft belt once myself. Did mine about 10-12 years ago.

The Ford SD truck and van 7.3 dual tensioners have different part numbers, are the same and as I recall, are priced differently at Ford.

RockAuto: 7.3 SD dual tensioner
Dayco 89257 $43.79
Gates 38191 54.89
Goodyear 49295 58.79
ACDelco 38191 61.79
Motorcraft BT-50 74.79
Ford F8UZ-6B209-CA (van part number), the truck number starts with F8TZ-6B209-xx

Belt: Motorcraft JK8-1227 (8 rib and 122-7/8" long) typically 2000 F-250SD 7.3 pickup.
 
#15 ·
Dave, any thoughts on why the modification lost its popularity?

It was quite simple, not very time consuming and it seems with the movement of both pulleys that the belt should stay tight.
 
#19 ·
I first read about it on TDS, I think. As people jumped from one diesel forum to another the information sort of got lost. I think it started life as an actual Ford Tech Service Bulletin (TSB).

As far as the belts go, RockAuto lists several lengths of belts for using the dual tensioner on SDs for the various combos: single alt, dual alt, ambulance.....You would have to measure the belt length for your truck as the SD trucks have the alternator and A/C compressor swapped left and right compared to an OBS and the two sets of engine brackets are different.

Motorcraft belts are identified thusly:

JK8-1227 the belt that fits my truck with SD dual tensioner. My truck is also a 1997 so it takes the later 8 rib serpentine belt instead of the earlier 7 rib belt.

JK8 serpentine 8 rib belt;
1227, the length in inches and 1/8" of inches, the belt is 122-7/8" long. The other Motorcraft serpentine belts are id'ed the same way.
 
#16 ·
Anyone do this conversion with the 215A ambulance alternator. Using the 215A already requires a longer belt.

Billy T.
gnxtc2@aol.com
 
#17 ·
#21 ·
Well it's the same number of pulleys (you're replacing the OBS tensioner and the ribbed idler, after all). But I think the main advantage is that the pivot point is _balanced_ between the two pulleys, whereas with the OBS tensioner, the one pulley is cantilevered off the pivot point. I had one OBS tensioner where the spring was still tight, and the bearing was still smooth, but as you released the spring to tension the belt, the angle would change, and the pulley would be out of alignment with the others. At the time, the SD tensioner was actually _cheaper_ than the OBS one. Alas no one locally had it in stock, and it was on the eve of a road trip, so our only choice was a long-arm OBS tensioner.

But yeah, you'd expect the new tensioner to be harder to wind up; that's just telling you that the old one had a weak spring.
 
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