tailgate window spring tension

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merrill77
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tailgate window spring tension

Post by merrill77 »

When I disassembled my tailgate, I found my lift was well greased with a re-manufactured motor that sounds like it is working well. Wiring appears to be in good condition with good connections. It sounded great going down and was very quick, but going up was slow, especially at the end.

I've read a bunch of posts about slow-raising tailgate windows but haven't seen anyone talk about the spring tension. When I pulled out my lift mechanism, I noticed that the springs seemed pretty weak. I tested with the weight of the window and find that they were offering very little help to the window. I'm assuming that their purpose is to counter the weight of the window so the motor has less work to do.

Sooooo... I moved the arms about 90 degrees past the full-up position (they crossed each other at this point). I unhooked the springs and backed them off a half turn on the shaft. Grabbed the other end with vice-grip pliers and torqued them back on. I doubted the wisdom of this approach at this point, as the tension is high enough that it was hard for me move the arms out. Without the mechanism attached to anything, I was afraid to try to get them all the way to the down position. I was unable to test with the window weight, so I just kept going. I attached the motor and used it to move the arms back to the up position. The motor struggled a bit going farther than that and it seemed like the plate was bending a bit under the torque. But I crossed my fingers and kept going, figuring (hoping) that the window weight would counter-act the additional spring torque.

I got it all back together and now the window goes up with a vengeance! Goes down a little slow, but still much faster than it went up before I made this change. Light pressure with a hand and it goes down quick...which is much easier than trying to pull it up :)

Here is a video of the window going up and down.
I am a little concerned that the extra tension on the mechanism is going to cause me a problem in the future. But I figure the 41-year-old springs will continue to loose a little of their force as the years go on. It appears the motor is working less hard going down now, than it was going up in the past. I am going to paste a warning note to the motor to remind myself not to disassemble the motor from the plate until the arms are de-tensioned. It would be dangerous with this much tension on them!

Chris


p.s. anyone know how to make the embed work on this forum?...this isn't working for me: [youtube]https://youtu.be/EoOCzij2qWA[/youtube]
Last edited by merrill77 on Mon Jun 18, 2018 5:32 am, edited 1 time in total.
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Re: tailgate window spring tension

Post by SJTD »

Don't the arms top out against a stop so the motor can be removed without a load on it? In other words you don't want to remove the motor with the arms down.
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Re: tailgate window spring tension

Post by merrill77 »

Not that I could see on mine.
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Curly
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Re: tailgate window spring tension

Post by Curly »

The service manual recommends putting a 1/4 inch bolt and nut in the mechanism to lock the arms down before you remove the motor. There are holes provided in the gear and arms for this.
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Re: tailgate window spring tension

Post by SJTD »

Opps. Again. Been a while since I reinstalled my motor.
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Re: tailgate window spring tension

Post by merrill77 »

Curly wrote:The service manual recommends putting a 1/4 inch bolt and nut in the mechanism to lock the arms down before you remove the motor. There are holes provided in the gear and arms for this.
Good to know for next time - thanks!
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Re: tailgate window spring tension

Post by HeavyMetalThunder_81 »

You say springs...as in more than one? Is there supposed to be two? Mine only has one and other doesn't look like there is room for a second on that other post.Image

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Re: tailgate window spring tension

Post by merrill77 »

Given that there are two posts with two stops corresponding to the two arms on the lift - yes, I am pretty confident that there should be one on each. That said, I didn't actually look this up in the TSM.
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Re: tailgate window spring tension

Post by HeavyMetalThunder_81 »

merrill77 wrote:Given that there are two posts with two stops corresponding to the two arms on the lift - yes, I am pretty confident that there should be one on each. That said, I didn't actually look this up in the TSM.
Did yours have two? The reason I ask is notice the reenforcement plate on the left side covers the recess that the second spring would normally sit in.

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-Jonny B.
1979 Cherokee Golden Eagle - UNDER CONSTRUCTION
7" lift, 35x12.5x15
AMC 401 - Pro-FLo 4 FI
NV4500/NWFBB/NP205 - Triple Stick'd
F D44 - 4.10, Eaton E-Locker
R M23 - 4.10, Detroit Locker

1979 Cherokee Chief - Parts
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Re: tailgate window spring tension

Post by merrill77 »

I didn't think I had a picture of this, but I went back and checked and found that I did. Yours does look a little different than mine.

Image

If you only have one spring and your window doesn't go up well, I'd guess that is part of the problem. This is the "before" picture. I added another half-turn because mine were so loose that they would fall off on their own without the wires put on by a PO/PM.
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Re: tailgate window spring tension

Post by Stuka »

If you only have on spring the window will want to go up crooked as the load won't be even. You should have two.
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Re: tailgate window spring tension

Post by HeavyMetalThunder_81 »

Stuka wrote:If you only have on spring the window will want to go up crooked as the load won't be even. You should have two.
Right, but it doesn't look like a second spring could even go there with that reenforcing plate in the way. Maybe Jeep switched to one spring later on?

I wonder if one could take a die grinder to it and cut out the area where the spring should sit and add a second spring.
-Jonny B.
1979 Cherokee Golden Eagle - UNDER CONSTRUCTION
7" lift, 35x12.5x15
AMC 401 - Pro-FLo 4 FI
NV4500/NWFBB/NP205 - Triple Stick'd
F D44 - 4.10, Eaton E-Locker
R M23 - 4.10, Detroit Locker

1979 Cherokee Chief - Parts
1979 Cherokee Chief - Parts
1979 Wagoneer - Sold
1981 Cherokee Chief - Cubed
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merrill77
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Re: tailgate window spring tension

Post by merrill77 »

Stuka wrote:If you only have on spring the window will want to go up crooked as the load won't be even. You should have two.
Not too sure about that - the two wheels are connected. The torque should be divided evenly...no? Roughly, anyway.
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Re: tailgate window spring tension

Post by merrill77 »

HeavyMetalThunder_81 wrote:
Stuka wrote:If you only have on spring the window will want to go up crooked as the load won't be even. You should have two.
Right, but it doesn't look like a second spring could even go there with that reenforcing plate in the way. Maybe Jeep switched to one spring later on?

I wonder if one could take a die grinder to it and cut out the area where the spring should sit and add a second spring.
Good point - based on those welds, it looks like mine could have been modified?
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Re: tailgate window spring tension

Post by Curly »

HeavyMetalThunder_81 wrote:
Stuka wrote:If you only have on spring the window will want to go up crooked as the load won't be even. You should have two.
Right, but it doesn't look like a second spring could even go there with that reenforcing plate in the way. Maybe Jeep switched to one spring later on?
I have a 77 Cherokee. The lift arms were completely worn out, way too much play in the arm pivots. It had 2 springs. I got a used replacement from Bob Stephens in Tucson, it only had one spring. My window goes up and down straight and smooth, so, Yes, I would bet that Jeep changed the design somewhere along the way.
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Re: tailgate window spring tension

Post by Stuka »

Curly wrote:
HeavyMetalThunder_81 wrote:
Stuka wrote:If you only have on spring the window will want to go up crooked as the load won't be even. You should have two.
Right, but it doesn't look like a second spring could even go there with that reenforcing plate in the way. Maybe Jeep switched to one spring later on?
I have a 77 Cherokee. The lift arms were completely worn out, way too much play in the arm pivots. It had 2 springs. I got a used replacement from Bob Stephens in Tucson, it only had one spring. My window goes up and down straight and smooth, so, Yes, I would bet that Jeep changed the design somewhere along the way.
I was thinking about it, and the lift arm gears mesh with the center gear, so they have to go up together.

I know my '75 had two springs. They had to have changed it at some point to "save money" :P
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Re: tailgate window spring tension

Post by SJTD »

Pretty sure mine only has one. I read somewhere that the later glass is thinner so only one spring. Not sure I buy that reason. Did the ones with metal trim have thicker glass and the trim?
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Re: tailgate window spring tension

Post by candymancan »

Just an fyi my 90 has one spring. and every grand wagoneer ive pulled parts from 86 87 three 88s a 90 and 89 all had one spring. and the window goes up fast and down fast. Although latetly its been hanging or pausing slightly going down the first inch. But thats not related to the spring the arms are probly crossing touching on a point.

Ive noticed though the windows on these Jeep dont go up nearly as fast as older 70s ones so when i watch videos.. and it cant be 8 old motors.. Now i know its probsbly due to one vs two springd
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)
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