ZF-6 Clutch Slipping After Mods
Thread Starter
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Mountain Pass
Joined: Aug 2016
Posts: 175
Likes: 37
ZF-6 Clutch Slipping After Mods
Hello,
Looking for clutch suggestions. Recently I performed these mods to my 1999.5 F250:
EBPV delete (with riffraff pedestal and outlet)
4" diamond eye turbo back straight pipe
Riffraff billet turbo wheel
hydra with php boxed tunes
in any tune except stock, my clutch slips around 1800-2000RPM in 4th and 5th (6-10lbs boost according to Forscan)
I have really only driven around with the 40hp dd tune as its PLENTY of power for me, even too much. I wish there was a 20hp tune lol.
I noticed getting onto the freeway, when warmed up, the clutch slips about 100-200RPM and then settles. Felt like an auto locking up in OD. If it was a 4r100 like my old truck, it would be a nice feel. But....its not.
I really like how smooth the clutch engages on this truck, but i also would like to have the confidence i can run this thing in at least the 40hdd and 40hp tow tunes with confidence when i go to use my 9,000 lb camper this summer.
Been looking at the South Bend 1944-6OK , or a LUK clutch (a brand i'm familiar with and have had nothing but good experiences in stock configurations)
Any one here running either one with beginner mods like me with good luck and smooth engagement?
I have stock turbo (except riffraff wheel)
stock injectors
35" tires
3.73 gears
Thanks in advance
-HP
Looking for clutch suggestions. Recently I performed these mods to my 1999.5 F250:
EBPV delete (with riffraff pedestal and outlet)
4" diamond eye turbo back straight pipe
Riffraff billet turbo wheel
hydra with php boxed tunes
in any tune except stock, my clutch slips around 1800-2000RPM in 4th and 5th (6-10lbs boost according to Forscan)
I have really only driven around with the 40hp dd tune as its PLENTY of power for me, even too much. I wish there was a 20hp tune lol.
I noticed getting onto the freeway, when warmed up, the clutch slips about 100-200RPM and then settles. Felt like an auto locking up in OD. If it was a 4r100 like my old truck, it would be a nice feel. But....its not.
I really like how smooth the clutch engages on this truck, but i also would like to have the confidence i can run this thing in at least the 40hdd and 40hp tow tunes with confidence when i go to use my 9,000 lb camper this summer.
Been looking at the South Bend 1944-6OK , or a LUK clutch (a brand i'm familiar with and have had nothing but good experiences in stock configurations)
Any one here running either one with beginner mods like me with good luck and smooth engagement?
I have stock turbo (except riffraff wheel)
stock injectors
35" tires
3.73 gears
Thanks in advance
-HP
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,356
Likes: 5,952
From: Lake Hartwell, GA
I run the SB 1939OHD which is the same clutch Wes444 has and the same as you are looking at, but the kit uses the OEM flywheel after it has been resurfaced.
The clutch has been performing great for many years towing a 5th wheel cross country.
They are pricey, but sometimes you get what you pay for.
I run PHP 65 HP tune with a Borg Warner turbo 100% of the time.
The clutch has been performing great for many years towing a 5th wheel cross country.
They are pricey, but sometimes you get what you pay for.
I run PHP 65 HP tune with a Borg Warner turbo 100% of the time.
Thread Starter
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Mountain Pass
Joined: Aug 2016
Posts: 175
Likes: 37
I run the SB 1939OHD which is the same clutch Wes444 has and the same as you are looking at, but the kit uses the OEM flywheel after it has been resurfaced.
The clutch has been performing great for many years towing a 5th wheel cross country.
They are pricey, but sometimes you get what you pay for.
I run PHP 65 HP tune with a Borg Warner turbo 100% of the time.
The clutch has been performing great for many years towing a 5th wheel cross country.
They are pricey, but sometimes you get what you pay for.
I run PHP 65 HP tune with a Borg Warner turbo 100% of the time.
How's the engagement vs stock? Is it pretty drivable when unloaded?
thanks,
-HP
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,356
Likes: 5,952
From: Lake Hartwell, GA
If you are going back in, you may want to consider some other things to change out or upgrade and save yourself the trip in the near future.
- Updated shift fork - https://www.riffraffdiesel.com/updat...f6-99-03-7-3l/
- Throw out bearing - Not sure on a source, but maybe @Wes444 is able to help based on this post.
- Pilot bearing/bushing - https://www.ford-trucks.com/forums/market/1754885
Thread Starter
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Mountain Pass
Joined: Aug 2016
Posts: 175
Likes: 37
If you are going back in, you may want to consider some other things to change out or upgrade and save yourself the trip in the near future.
- Updated shift fork - https://www.riffraffdiesel.com/updat...f6-99-03-7-3l/
- Throw out bearing - Not sure on a source, but maybe @Wes444 is able to help based on this post.
- Pilot bearing/bushing - https://www.ford-trucks.com/forums/market/1754885
- Updated shift fork - https://www.riffraffdiesel.com/updat...f6-99-03-7-3l/
- Throw out bearing - Not sure on a source, but maybe @Wes444 is able to help based on this post.
- Pilot bearing/bushing - https://www.ford-trucks.com/forums/market/1754885
I would think that there is a good reason South Bend goes with the kevlar?
Has there been issues with the bearings supplied in the SBC kits?
Last time did a clutch was on a small block chevy 350 in a '75 blazer. This project is worrying me a little bit!
Logistics Pro
Joined: May 2017
Posts: 4,667
Likes: 1,455
From: Muskogee, Ok
Nice, thanks to Sous' post I don't need to link my clutch thread 
Like Jeff said we have the same "clutch", but different kits/part numbers. The friction disks and pressure plates are the same, but the 44 comes with their flywheel so if a resurface of the original is something you don't have time or access to get the 44 and you can bolt it up and go.
Their flywheel came with their totally junk "kevlar" (aka white plasticy splooge from a troll) bushing pressed into the flywheel so I went with the Fitzall bearing since the oilite bushings were a custom thing that no one was making when I needed mine done
PEdal engagement required a touch more effort. Their TO bearing is all metal vs the stock composite one
Like Jeff said we have the same "clutch", but different kits/part numbers. The friction disks and pressure plates are the same, but the 44 comes with their flywheel so if a resurface of the original is something you don't have time or access to get the 44 and you can bolt it up and go.
Their flywheel came with their totally junk "kevlar" (aka white plasticy splooge from a troll) bushing pressed into the flywheel so I went with the Fitzall bearing since the oilite bushings were a custom thing that no one was making when I needed mine done
PEdal engagement required a touch more effort. Their TO bearing is all metal vs the stock composite one
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Logistics Pro
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From: Muskogee, Ok
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FTE Leadership Emeritus
Joined: May 2014
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From: Lake Hartwell, GA
Thread Starter
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Mountain Pass
Joined: Aug 2016
Posts: 175
Likes: 37
Today I was driving home, and it started slipping a little easier than yesterday. I feel like I better start ordering parts.
My beautiful wife reminded me that when i replaced my turbo pedestal(on the 1st attempt), the o-rings didn't seat properly and i spilled about 2 qts of oil down the back of the motor, and that might be why its slipping.
Have you guys heard of that happening due to oil spills?
In that case is this thing totally toasted or is there hope the oil might burn away and the clutch will start grabbing better again?
not super hopeful about that possibility...
Thanks for all your input and invaluable experiences!
-HP
My beautiful wife reminded me that when i replaced my turbo pedestal(on the 1st attempt), the o-rings didn't seat properly and i spilled about 2 qts of oil down the back of the motor, and that might be why its slipping.
Have you guys heard of that happening due to oil spills?
In that case is this thing totally toasted or is there hope the oil might burn away and the clutch will start grabbing better again?
not super hopeful about that possibility...
Thanks for all your input and invaluable experiences!
-HP
Laughing Gas
Joined: Jun 2017
Posts: 835
Likes: 126
From: CSRA, SC
Nope. If you really did get oil on the clutch its permanently hooped. The fibers of the friction disc are permanently impregnated with slippy goo. That could be the problem but my guess is your clutch is just worn/glazed such that it barely worked and then once you added some ponies it wasn't enough. If you did get oil on it I think you would have noticed a long time ago.
I should add, once the clutch starts slipping once, it will slip more often and more easily every time since the heat will glaze the clutch more and more each time until it's useless.
I should add, once the clutch starts slipping once, it will slip more often and more easily every time since the heat will glaze the clutch more and more each time until it's useless.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,356
Likes: 5,952
From: Lake Hartwell, GA
Fatal flaw in the valley drain design in a manual transmission truck. See links below...
Thread Starter
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Mountain Pass
Joined: Aug 2016
Posts: 175
Likes: 37
Well I bit the bullet and bought a South bend 1944-6OK Clutch Kit with a new flywheel.
I was looking at my up-pipes, they are not bellowed, but also not leaking. I'm really on the fence about replacing them. (did it on my last truck and lost a bit of skin off my knuckles even with the transmission out)
Definitely going to do some version of the drain-tube mod while I'm in there though.
I did a rear main seal on my last truck also, so I'm ready for that if it calls for it. local shop down the road has the motorcraft seals in stock.
Its going to be a fun weekend!
I was looking at my up-pipes, they are not bellowed, but also not leaking. I'm really on the fence about replacing them. (did it on my last truck and lost a bit of skin off my knuckles even with the transmission out)
Definitely going to do some version of the drain-tube mod while I'm in there though.
I did a rear main seal on my last truck also, so I'm ready for that if it calls for it. local shop down the road has the motorcraft seals in stock.
Its going to be a fun weekend!