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Micah@OST

How To Make Your 6-Speed Wot Shift

33 posts in this topic

After our experience with Howie's car we learned a lot about making these 6-speed cars WOT shift. I have seen countless threads on the issue and have read many during my own research and I think it's time to share what we have learned. Hopefully it will save others some frustration and time.

 

At ChallengerFest 7 the car was having trouble shifting at WOT. This issue did not reveal itself until we got to Kentucky; we did many WOT shifts on the dyno and on the street without issue. Once we got the car back we pulled the transmission and found one of the brackets for the floater plate had sheared off. We still do not know if it was this or the expansion of the clutch material due to heat that kept us from WOT shifting.

 

After getting the clutch repaired we started our research on getting this car to shift properly. To test the clutch engagement the transmission was placed in first, the clutch bled, and with the shifter removed I reached through the hole in the trans tunnel and turned the output shaft by hand while depressing the clutch pedal. I noted when the clutch would disengage and by how much. This was repeated for each attempt.

After the clutch was repaired and before it was installed on the car, it was placed on a drill press to see how and when the clutch discs were released. Using the head of the drill with a custom adapter to press the clutch fingers, we noted that after 1/2" of travel the disks were completely disengaged. At no point did the clutch "roll over" and start to re-engage the disks.

 

Testing was done using the following parts:

Clutch - McLeod unit for a Viper mounted on a custom McLeod flywheel

Transmission - RPM Level 7

 

Control: The repaired clutch was installed and the transmission was placed in the car with no changes to the TOB. Clutch disengagement was had at 3/4" from the floor. Even at that point the output shaft did not spin freely and there was a noticeable amount of drag.

First attempt: I drew up some shims in CAD and had them cut in different thicknesses. All the measurements were done and the proper shims were selected. After being installed behind the TOB everything was offered up to the car. We noticed no change in the relationship between clutch disengagement and pedal position. The output shaft still had the same amount of drag as with the control. We repeated this process with all sorts of different shim stacks with no change at all. I have to believe that using shims to change the starting point of the TOB will not do anything to help shifting unless your TOB reaches its limit of travel at some point in the clutch throw.

Second attempt: We repeated our first attempt with a new TOB as suggested by different shops. This had no effect.

Third attempt: We caved and ordered an extended throw TOB from McLeod with the promise that "it will fix it". Lo and behold, the TOB did not bolt to the transmission or hook up to the clutch line. Calling McLeod again they said, in short, "We've never sold or made one for a Challenger and thought the Mustang unit would fit. It's the best we can do right now." Rather bummed, we got to work fabricating the Mustang unit to fit the transmission and creating a custom fitting to attach the factory clutch line. After installation clutch disengagement occurred halfway through pedal travel. When the pedal was on the floor, the output shaft spun freely and would continue to spin after I let go of it. Perfect!

In conclusion, an extended throw TOB seems to be the cure for all of you out there having trouble WOT shifting your cars on aftermarket clutches. If you need a customized McLeod TOB for your car please let me know. $580 plus shipping should do the trick.

If anyone has questions or wants more details let me know! I'll do my best to help as I know how difficult it was to find solid information on this subject.

 

Edit: I have been getting a lot of inquiries about the modified throwout bearings. I have added them to the website. They can now be ordered here: http://www.ostdyno.com/products/drivetrain/

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Control: The repaired clutch was installed and the transmission was placed in the car with no changes to the TOB. Clutch disengagement was had at 3/4" from the floor. Even at that point the output shaft did not spin freely and there was a noticeable amount of drag.

 

Remind me, this is a tr6060 based rpm transmission and I know you said McLeod clutch and the disengagement is 3/4" from the FLOOR, not the top of clutch travel?

 

Obvioulsy we have not had ours off and measured but that is not where it feels like ours disengages. And yes this is a funny statement to make but what my feet "feel" could be a lot different than what you measure and I am sure your measurements are correct. You are one hell of a mechanic and car development expert as testified by the cat you built Howie. As a driver I have worked my way to the third aftermarket clutch. Each usually start off feeling like disengagememt is close to the floor but over time it gets closer and closer to the top. We just switched to the McLeod and it has already migrated to almost the top of travel. And maybe I am missing your point. Is where the clutch feels like it is fully disengaged by the driver and where it is actually fully disengaged two radically different places?

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Remind me, this is a tr6060 based rpm transmission and I know you said McLeod clutch and the disengagement is 3/4" from the FLOOR, not the top of clutch travel?

 

Obvioulsy we have not had ours off and measured but that is not where it feels like ours disengages. And yes this is a funny statement to make but what my feet "feel" could be a lot different than what you measure and I am sure your measurements are correct. You are one hell of a mechanic and car development expert as testified by the cat you built Howie. As a driver I have worked my way to the third aftermarket clutch. Each usually start off feeling like disengagememt is close to the floor but over time it gets closer and closer to the top. We just switched to the McLeod and it has already migrated to almost the top of travel. And maybe I am missing your point. Is where the clutch feels like it is fully disengaged by the driver and where it is actually fully disengaged two radically different places?

 

Thank you for the compliments! Much appreciated :)

 

Yes, this is an RPM TR6060 and a McLeod clutch. I have updated the original post to contain that information.

 

As far as your "migrating" clutch engagement I can only think of two things that would cause that. The first is improper bleeding when installed. As you drive the car more the clutch may eventually become bled properly and disengagement occurs at the beginning of the throw. The second would be that somehow the disks are "cleaned" of some sort of material making engagement change. I don't know if I have a lot of faith in this second explanation though as it seems unlikely.

 

Having a clutch engage near the top is actually what you want! As long as it's not so close to the top that the clutch never actually engages.

 

Actual clutch engagement and the "feel" of the clutch engaging are definitely going to be different. I would consider clutch engagement to be the point where, if one were turning the output shaft by hand, enough resistance was met that you could not easily turn the output shaft. The power of the engine (which is much greater than my hand) combined with the weight of the car will obviously make this point seem much farther up in the clutch stroke as it will take a lot more clutch engagement to roll the car forward or lug the engine. It is definitely important to confirm where actual clutch engagement is because that will give you better data without all the other variables chucked in (car's weight, rolling resistance, drivetrain loss, engine power, etc.).

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I's not sure what she's talking bout "migration" We did have an issue with the CF clutch where we had some dragging at first that seemed to go away after pumping a couple hundred times. Then we had the clutch go up in smoke in the burnout box in Arkansas after which it would not engage. When I say "up in smoke" it was not a huge smoke show. 

 

When we pulled the Centerforce it looks almost brand new. From what I can tell it was barely engaging and the combination of the big R7's and the very grippy surface at Blytheville took away the little resistance it had. 

 

When I have that clutch out and look at it, it looks almost new. There is some material on the very edge of the discs that seems to have been a bit high and broke away rather than wear. When all stacked on the bench with the PP all the way free, I can freely spin the discs. It seems to me that the standoffs for the PP are just too tall. I would think they should be a lot shorter for the clutch to engage the flywheel throughout it's life. 

 

I will try to get some pick of it. Point is that there seems to be issues with more than one of the aftermarket. 

 

FWIW, I never had any engage/disengage issues with the Spec, just that the drivability overall sucked. 

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Great write-up and research, Micah.  I wonder if this is the reason mine will not take a flatfoot shift, and the transmission is getting worse and worse.  I'm running the McLeod and a quicktime bell housing, but I never did take the time to measure anything, as I was assured it was a bolt and go operation. 

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Great write-up and research, Micah.  I wonder if this is the reason mine will not take a flatfoot shift, and the transmission is getting worse and worse.  I'm running the McLeod and a quicktime bell housing, but I never did take the time to measure anything, as I was assured it was a bolt and go operation. 

 

Thank you.

 

We were told the same as you and as you can see, that was not the case.

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Great write-up and research, Micah. I wonder if this is the reason mine will not take a flatfoot shift, and the transmission is getting worse and worse. I'm running the McLeod and a quicktime bell housing, but I never did take the time to measure anything, as I was assured it was a bolt and go operation.

I thought the same thing w/ my McLeod, $2400 later in repairs to my previously bought RPM transmission as most are aware of and well you know the rest.... but I will still say if it's said to fit specific year/makes, then that is telling me you did the work for me to be spec'd to fit for my vehicle OR tell me on the instructions that it's to be treated like a universal fit for measurement.

 

 

Sent from my iPhone using Tapatalk

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Thank you for the compliments! Much appreciated :)

 

Yes, this is an RPM TR6060 and a McLeod clutch. I have updated the original post to contain that information.

 

As far as your "migrating" clutch engagement I can only think of two things that would cause that. The first is improper bleeding when installed. As you drive the car more the clutch may eventually become bled properly and disengagement occurs at the beginning of the throw. The second would be that somehow the disks are "cleaned" of some sort of material making engagement change. I don't know if I have a lot of faith in this second explanation though as it seems unlikely.

 

Having a clutch engage near the top is actually what you want! As long as it's not so close to the top that the clutch never actually engages.

 

Actual clutch engagement and the "feel" of the clutch engaging are definitely going to be different. I would consider clutch engagement to be the point where, if one were turning the output shaft by hand, enough resistance was met that you could not easily turn the output shaft. The power of the engine (which is much greater than my hand) combined with the weight of the car will obviously make this point seem much farther up in the clutch stroke as it will take a lot more clutch engagement to roll the car forward or lug the engine. It is definitely important to confirm where actual clutch engagement is because that will give you better data without all the other variables chucked in (car's weight, rolling resistance, drivetrain loss, engine power, etc.).

I's not sure what she's talking bout "migration" We did have an issue with the CF clutch where we had some dragging at first that seemed to go away after pumping a couple hundred times. Then we had the clutch go up in smoke in the burnout box in Arkansas after which it would not engage. When I say "up in smoke" it was not a huge smoke show.

 

When we pulled the Centerforce it looks almost brand new. From what I can tell it was barely engaging and the combination of the big R7's and the very grippy surface at Blytheville took away the little resistance it had.

 

When I have that clutch out and look at it, it looks almost new. There is some material on the very edge of the discs that seems to have been a bit high and broke away rather than wear. When all stacked on the bench with the PP all the way free, I can freely spin the discs. It seems to me that the standoffs for the PP are just too tall. I would think they should be a lot shorter for the clutch to engage the flywheel throughout it's life.

 

I will try to get some pick of it. Point is that there seems to be issues with more than one of the aftermarket.

 

FWIW, I never had any engage/disengage issues with the Spec, just that the drivability overall sucked.

 

 

So Micha I have been driving our newely installed McLeod and can easily shift it with the clutch depressed about 1/3 from the top of travel. Any way there is that much difference in manufacturing tolerances between our unit and the one you have installed in Howie's car? I understand your point about what I feel when driving vs having it out and the shaft turning easily but I can't imagine the delta being 2/3 of clutch travel. Likely I am wrong, again. Just hard concept to grasp.

 

As for Chuck not remebering, the Spec Definetely had an issue as far as engagement point migrating. It started at the floor and moved almost all the way to the top. And Micha, if I remember correctly your first explanation about bleeding it sounds vaugley familiar and that may have been the issue we encountered. It may have been the only one with that issue. I most likely confused the Spec issue with the dragging issue Chuck desribes on the Centerforce. Sorry to confuse the sibject. The McLeod definetely has not moved like the Spec did.

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Good stuff Micah.  Should help a lot of folks.  Too bad it's so hard to just get straight answers on these cars from parts vendors.  Mine seems to still be doing OK from it's last outing.  If I start having issues again I'm gonna holler at you for one of these modified TOBs.

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On 10/20/2016 at 9:53 PM, BayouTigress said:

So Micha I have been driving our newely installed McLeod and can easily shift it with the clutch depressed about 1/3 from the top of travel. Any way there is that much difference in manufacturing tolerances between our unit and the one you have installed in Howie's car? I understand your point about what I feel when driving vs having it out and the shaft turning easily but I can't imagine the delta being 2/3 of clutch travel. Likely I am wrong, again. Just hard concept to grasp.

 

As for Chuck not remebering, the Spec Definetely had an issue as far as engagement point migrating. It started at the floor and moved almost all the way to the top. And Micha, if I remember correctly your first explanation about bleeding it sounds vaugley familiar and that may have been the issue we encountered. It may have been the only one with that issue. I most likely confused the Spec issue with the dragging issue Chuck desribes on the Centerforce. Sorry to confuse the sibject. The McLeod definetely has not moved like the Spec did.

 
I'd say there could definitely be that much of a difference especially considering we are using two different clutches. One can set up a clutch to have tighter clamping force as well which will effect engagement.
 
As for the Spec changing engagement over time, I just had a Viper in the shop with a Spec clutch and the same issue. Interesting.

 

On 10/21/2016 at 4:56 PM, Speedy said:

Good stuff Micah.  Should help a lot of folks.  Too bad it's so hard to just get straight answers on these cars from parts vendors.  Mine seems to still be doing OK from it's last outing.  If I start having issues again I'm gonna holler at you for one of these modified TOBs.

 

Sounds good, buddy! My thoughts exactly. I hope this helps some people who were as frustrated I was.

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You guys definitely get cudos on this. Wonder how different the throw is from clutch to clutch.

 

Thank you!

 

The throw will definitely depend on each clutch's point of disengagement. Even two aftermarket clutches of the same part number can have different disengagement points depending on how tight they are set up from the factory. Almost everybody's setup and throw will be different unless they are running standard shelf parts.

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Fluid type and condition can also play a part in all of this. I basically need to change mine every spring, it gets moisture in it over winter somehow. I've been using Motul rbf600.

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Something to share and a question for Micah....

 

I've been having the same disengagment issues with both a McLeod and lately a CenterForce.  I was about to throw up my hands and just go the route of an OEM Hellcat clutch......

 

In the process of investigating part numbers, I've learned that the Hellcat uses a different clutch master than the R/T, Scat Pack, etc.....

 

Before taking the plunge on the Hellcat PP, disc, clutch master, etc, I ordered a clutch master and installed it (with my CF clutch)..... I can't say that it has eliminated 100% of the disengagement issue, but it has definitely made a noticeable improvement without any perceptible increase in pedal pressure IMO.

 

Maybe you might want to continue your R&D by putting a Hellcat clutch master in the mix and see if that further improves anything?  If you do let me know I will share the p/n with you.

 

My question:  Does the McLeod TOB that you are offering include the adapter fittings to allow it to fit up with the Challenger?

 

thanks-

rich

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Something to share and a question for Micah....

 

I've been having the same disengagment issues with both a McLeod and lately a CenterForce.  I was about to throw up my hands and just go the route of an OEM Hellcat clutch......

 

In the process of investigating part numbers, I've learned that the Hellcat uses a different clutch master than the R/T, Scat Pack, etc.....

 

Before taking the plunge on the Hellcat PP, disc, clutch master, etc, I ordered a clutch master and installed it (with my CF clutch)..... I can't say that it has eliminated 100% of the disengagement issue, but it has definitely made a noticeable improvement without any perceptible increase in pedal pressure IMO.

 

Maybe you might want to continue your R&D by putting a Hellcat clutch master in the mix and see if that further improves anything?  If you do let me know I will share the p/n with you.

 

My question:  Does the McLeod TOB that you are offering include the adapter fittings to allow it to fit up with the Challenger?

 

thanks-

rich

 

That's interesting. So interesting that I had to look into it myself. I found that the part numbers for the Hellcat and RT/SRT seem to be interchangeable. This page copied from Dealer Connect (Chrysler's tech pages) shows the parts can be interchanged but it does list them for different engines. Maybe there's something here?

 

Yes, the TOB is modified to bolt to the transmission and hook up to the factory clutch line. The functionality and main body of the unit are left untouched.

post-1833-0-93825200-1477397749_thumb.jpg

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That's interesting. So interesting that I had to look into it myself. I found that the part numbers for the Hellcat and RT/SRT seem to be interchangeable. This page copied from Dealer Connect (Chrysler's tech pages) shows the parts can be interchanged but it does list them for different engines. Maybe there's something here?

 

I think there might be otherwise why different p/n for the master but not the slave?

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It very well could be for a different pedal feel or something completely unrelated. But it could also be for more disengagement. I would then wonder why Dodge just didn't put this MC in all the cars if it worked better. 

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FYI, the 6 speed Hellcat has a MUCH heavier pedal than my R/T with McLeod clutch.  Like 400% stiffer pedal heavier.  I wasn't sure if that was due to the clutch or something else.

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I have been using a 7/8 bore Wilwood with good results, iirc the Vipers were 3/4 bore on pre 08's. Would be nice if the bore sizes were known.

 

would you mind if I asked which one? kind of interested in seeing what's out there....

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I Have to ask I have my engine out because It was rebuilt by Jeff Taylor so this is the perfect time to replace my TOB. I just replaced my stock clutch with a Mcleod and noticed if wasn’t shifting right between first and second (Hard shift like not totally disengaging) before the engine rebuild. I burned out  some Aluminum shims to place behind the TOB for the fix. Sounds like you have a better fix. Will it work on a stock 6sp with the McLeod? If so, are they in stock??

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I Have to ask I have my engine out because It was rebuilt by Jeff Taylor so this is the perfect time to replace my TOB. I just replaced my stock clutch with a Mcleod and noticed if wasn’t shifting right between first and second (Hard shift like not totally disengaging) before the engine rebuild. I burned out  some Aluminum shims to place behind the TOB for the fix. Sounds like you have a better fix. Will it work on a stock 6sp with the McLeod? If so, are they in stock??

 

We tried the shim trick as well with some CAD drawn and water-jetted shims. No luck.

 

Yes, this will work with a factory transmission. Each TOB is made to order. Check out the link to our website on the first page to place your order. I can have one modified as soon as McLeod gets a TOB to me.

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