driveline movement
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Senior User
Joined: Aug 2013
Posts: 355
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From: Peoria IL
The tranny was brand new when I got the truck. It is securely bolted to the cross member. I wonder if the cross member is loose?
The guy said he was going to "check that everything was tight" as it had been a week since the new tranny was added.
I need to get this thing on a lift. Something has to be loose.
The guy said he was going to "check that everything was tight" as it had been a week since the new tranny was added.
I need to get this thing on a lift. Something has to be loose.
Thread Starter
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Senior User
Joined: Aug 2013
Posts: 355
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From: Peoria IL
So the shift linkage is a rod that goes from the column to the trans.
I pull down from park to drive. The rod goes down & the tranny is in drive.
When I hit the gas the shifter on the column pulls down from drive into 2nd. & the tranny goes from 1st to 2nd @ the same time.
It's almost like the tranny is pushing forward while the hard shift rod is staying put forcing the trans to shift down into 2nd.
I know the *** squats big time & the engine is tight.
I wish my pics had saved.
The cross member has to be moving.
The rear end is hard mounted to a welded in cross member. I can't see that flexing under torque & the yolk has about 2 inches of play if it did.
I pull down from park to drive. The rod goes down & the tranny is in drive.
When I hit the gas the shifter on the column pulls down from drive into 2nd. & the tranny goes from 1st to 2nd @ the same time.
It's almost like the tranny is pushing forward while the hard shift rod is staying put forcing the trans to shift down into 2nd.
I know the *** squats big time & the engine is tight.
I wish my pics had saved.
The cross member has to be moving.
The rear end is hard mounted to a welded in cross member. I can't see that flexing under torque & the yolk has about 2 inches of play if it did.
Hotshot
Joined: Oct 2004
Posts: 15,882
Likes: 88
From: Durham NC
The rear end squat on hard launches is a design characteristic of the Jag IRS. It was designed for high speed cornering, not drag racing. If your intent is/was to do drag launches this was the wrong rear suspension choice, you would have been better served by a solid axle with 4 link, or ladder bars.
More Turbo
Joined: Nov 2013
Posts: 557
Likes: 8
From: arkansas
My cousin had a 70 f100 that would shell a rear u joint everytime he nailed it.After much frustration,we pulled the rear springs..They were so worn they would flatten completely just by standing on them.New springs solved the problem.
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Senior User
Joined: Aug 2013
Posts: 355
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From: Peoria IL
I think the rear squatting is probably not the cause just a quirk of the hot rod rear end.
I'm now leaning toward a loose trans crossmember. If the trans is climbing off the mount an inch, maybe less, it would be enough to down shift.
When it goes into 2nd I lose torque & the tranny drops back in place pulling the shift lever from drive to 2.
That would sure explain it
I'm now leaning toward a loose trans crossmember. If the trans is climbing off the mount an inch, maybe less, it would be enough to down shift.
When it goes into 2nd I lose torque & the tranny drops back in place pulling the shift lever from drive to 2.
That would sure explain it
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More Turbo
Joined: Nov 2013
Posts: 557
Likes: 8
From: arkansas
Probably not,just throwing that out there,i never would of thought tbat it could have been the problem with his,but sometimes we got to think outside of the normal.A loose crossmember may be your gremlin.Good luck on finding it.
Hotshot
Joined: Oct 2004
Posts: 15,882
Likes: 88
From: Durham NC
A lot of the suggestions being thrown around keep missing the fact that Brassmonkey is running a JAG IRS not a solid axle or leaf springs. Changing the coilovers would just make the ride harsher not make the geometry behave any differently. The Jag IRS is not designed for drag launches, the geometry makes it squat.
BM, you shouldn't be using IFS, IRS with out sway bars!
Put the SJ6/12 stock sway bar on the rear and a front bar the diameter of the Jag front that fits on the front. But sway bars alone won't stop body roll. That's the function of the shocks entering and exiting a corner, the sway bar doesn't affect the roll until mid corner.
The truck is always going to have a lot of roll, both actual and perceived. Actual because by nature it has a high roll center, and perceived because you are sitting higher than that roll center, like sitting on an upper deck of a boat in a rough sea it will feel like you are rolling more than if you were sitting low.
BM, you shouldn't be using IFS, IRS with out sway bars!
Put the SJ6/12 stock sway bar on the rear and a front bar the diameter of the Jag front that fits on the front. But sway bars alone won't stop body roll. That's the function of the shocks entering and exiting a corner, the sway bar doesn't affect the roll until mid corner.The truck is always going to have a lot of roll, both actual and perceived. Actual because by nature it has a high roll center, and perceived because you are sitting higher than that roll center, like sitting on an upper deck of a boat in a rough sea it will feel like you are rolling more than if you were sitting low.
Posting Guru
Joined: Sep 2012
Posts: 1,314
Likes: 1
A lot of the suggestions being thrown around keep missing the fact that Brassmonkey is running a JAG IRS not a solid axle or leaf springs. Changing the coilovers would just make the ride harsher not make the geometry behave any differently. The Jag IRS is not designed for drag launches, the geometry makes it squat.
BM, you shouldn't be using IFS, IRS with out sway bars! Put the SJ6/12 stock sway bar on the rear and a front bar the diameter of the Jag front that fits on the front. But sway bars alone won't stop body roll. That's the function of the shocks entering and exiting a corner, the sway bar doesn't affect the roll until mid corner.
The truck is always going to have a lot of roll, both actual and perceived. Actual because by nature it has a high roll center, and perceived because you are sitting higher than that roll center, like sitting on an upper deck of a boat in a rough sea it will feel like you are rolling more than if you were sitting low.
BM, you shouldn't be using IFS, IRS with out sway bars!
Put the SJ6/12 stock sway bar on the rear and a front bar the diameter of the Jag front that fits on the front. But sway bars alone won't stop body roll. That's the function of the shocks entering and exiting a corner, the sway bar doesn't affect the roll until mid corner.The truck is always going to have a lot of roll, both actual and perceived. Actual because by nature it has a high roll center, and perceived because you are sitting higher than that roll center, like sitting on an upper deck of a boat in a rough sea it will feel like you are rolling more than if you were sitting low.
And, unless you want serious repair bills, you shouldn't ever try to "launch"
with that rear end.
Thread Starter
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Senior User
Joined: Aug 2013
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From: Peoria IL
Man you guys are bumming me out!
Great advice though & I really appreciate it.
I happened to come across an old rusty Ford Bronco (91) I will take a look @ the sway bar setup on it & see what I need to do.
Great advice though & I really appreciate it.
I happened to come across an old rusty Ford Bronco (91) I will take a look @ the sway bar setup on it & see what I need to do.