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  #1  
Old 04-22-2001, 12:45 AM
blackjeep2002 blackjeep2002 is offline
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I have a 78 Cherokee with a QT that I am planning to replace with a Dana 18. Anyone have experience with this swap as far as things to look out for?
Thanks,
Keith
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  #2  
Old 04-22-2001, 04:48 AM
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Rande Rande is offline
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I haven't done this swap but I can tell you the Dana18 will not bolt up in place of a QT. You will need an adapter to mate the D18 to the T-400 tranny, you may also need driveshaft modifications and obviously you will need to cut a hole in the floor for the D18 shifter. That adapter is gonna be costly, and will likely intail changing the output shaft of the tranny wich means it comes out and gets disassembled. Lotsa work and expense.
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  #3  
Old 04-22-2001, 05:43 AM
Mike Z Mike Z is offline
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Aren't the differential housings in a different place also, on a QT jeep?
MikeZ
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  #4  
Old 04-22-2001, 06:17 AM
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Rande Rande is offline
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The QT and the D18 both have the rear driveshaft offset to the passenger side so that is not a concern in this particular swap. The D20 has the rear driveshaft inline with the tranny and that would then be of some concern. I, personally, don't see that as a problem though as your univeral joints will work if the driveshaft is offset up and down or side to side or any combination thereof. Lots of people worry about that driveshaft offset but I just don't understand why there is any concern, 'course I'm no engineer (though, I DID drive by a Holiday Inn this morning).
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  #5  
Old 04-22-2001, 06:41 AM
River Beast River Beast is offline
 
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I am looking into this right now myself... the adapter kit which comes with a TH400 output shaft, support bearing and adapter plate is about $600 from www.advanceadapters.com and $495 from www.novak-adapt.com

The strongest D18 is the one with the 1 1/4" intermediate shaft.... the others, 3/4" and 1" are smaller, thus weaker. You cannot use a D18 that was mated to a standard tranny unless you can find the input gear to replace in the D18 that is used with the auto tranny. there is also the different size locating bores... 3" and 4".... I have been told that the 4" locating bore will work for the TH400.

I got most of my info from Scotty Probert... a WEALTH of knowledge... hopefully he will elaborate here for us....there is sooo much to learn from others

------------------
Todd
"River Beast"

14" of total Lift on 39.5" Swampers
44's locked with 4.89's
...and other stuff...
My Original FSJ site
riverbeast@earthlink.net

"When approaching an intersection, remember...
the vehicle with the BIGGEST TIRES has the right of way..."


'93 3/4 ton 4x4 Suburban...a.k.a. "FSJ Hauler"
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  #6  
Old 04-22-2001, 06:46 AM
River Beast River Beast is offline
 
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<BLOCKQUOTE>quote:</font><HR>Originally posted by Rande:
...I, personally, don't see that as a problem though as your univeral joints will work if the driveshaft is offset up and down or side to side or any combination thereof. Lots of people worry about that driveshaft offset but I just don't understand why there is any concern...<HR></BLOCKQUOTE>


Rande... the concern with the offset rear and the center output D20 is that you create a compound angle. This type of angle would require rear CV shaft (CV at the the T-case) to ensure the cancellation of all vibes. Every area of research I have found state this very thing. Furthermore, any u-joint angles that are more than 2 degrees in difference of one another will have vibes. U-loints need to be within 2 degrees of each other to cancel out vibes.


------------------
Todd
"River Beast"

14" of total Lift on 39.5" Swampers
44's locked with 4.89's
...and other stuff...
My Original FSJ site
riverbeast@earthlink.net

"When approaching an intersection, remember...
the vehicle with the BIGGEST TIRES has the right of way..."


'93 3/4 ton 4x4 Suburban...a.k.a. "FSJ Hauler"
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  #7  
Old 04-22-2001, 07:50 AM
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Rande Rande is offline
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What compound angle? Your u-joints don't care what direction the driveshaft is pointed. Wether it is pointed down, up or to the side should not matter at all.
I have seen this on all sorts of farm equipment driven from a pto on the tractor. All sorts of angles. As long as the driving shaft (at the tranny) and the driven shaft (at the pinion) are within a few dergrees of pointing in the same direction, the u-joints don't care which way the driveshaft is pointing. See what I mean? Wether the driveshaft is pointing up, down, left, right or somewhere in between, shouldn't matter at all.

[This message has been edited by Rande (edited April 22, 2001).]
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  #8  
Old 04-22-2001, 08:16 AM
Mikel2
 
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<BLOCKQUOTE>quote:</font><HR>Originally posted by Rande:
The QT and the D18 both have the rear driveshaft offset to the passenger side so that is not a concern in this particular swap. The D20 has the rear driveshaft inline with the tranny and that would then be of some concern. I, personally, don't see that as a problem though as your univeral joints will work if the driveshaft is offset up and down or side to side or any combination thereof. Lots of people worry about that driveshaft offset but I just don't understand why there is any concern, 'course I'm no engineer (though, I DID drive by a Holiday Inn this morning).<HR></BLOCKQUOTE>



You are right (I think). I swapped my TH400/QT with a T-18A/Dana 20 and I was also worried about driveline angles. I have 4in lift, and now the the diff is not aligned witht the TC output. If you think about it, the driveline angle due to my lift is pretty much the same as that caused by the diff being in the wrong side. But you only have one angle, only that it is rotated. Do I make any sense??

Mikel


------------------
1978 Jeep Cherokee Chief
360 4bbl/T18A/Dana 20
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  #9  
Old 04-22-2001, 08:19 AM
Mikel2
 
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Rande,
I think Todd is right. A U-joint will work at any angle below a maximum. But the greater the angle, the less uniform that angular speed will become. If you have two U-joints working at the same angle, they (I think) will cancel out that variation in angular velocity.
Mikel


------------------
1978 Jeep Cherokee Chief
360 4bbl/T18A/Dana 20
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  #10  
Old 04-22-2001, 09:08 AM
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scotty scotty is offline
 
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i would tend to agree on the u joint issue.a dual plane angle is a human perspective-up/down and left/right. i dont think the driveshaft knows(or cares) if its angle is horizontal,vertical,or something in between. as mentioned,the inportant thing is for the maximum operating angle to not be exceeded,and for the angle to be the same at both end. if you move your centered diff 6 inches to the left,its angle and the new angle created at the t case should still equal 80 degrees. i have known lots of people to swap a centered xfer inplace of a QT and let the driveshaft run over with no prollems.

on the spicer 18 swap,you cannot do it with factory parts. it is true that they both share the "texas" pattern,and it seems that you could swap one onto a factory 20 adapter. this part is true,but there are a couple other prollems:1) the 18 will most likely have the smal index hole of about 3 inches. the dana 20 has a 4 inch index hole. while this can be solved by swapping the 18 guts into a 20 housing(which requires the 18 to be the later version with a 1.25 inch intermediate shaft) or finding the rare version of the 18 that has a 4 bore, this brings the 2nd prollem: 2)an 18 and 20 input gear are different. the gear is not swappable onto the factory th400/d20 tailshaft. the factory 20 gear has a wierd internal spline count. the 18 input gear has either 6(most common) or 10 internal splines. therefore an aftermarket kit must be purchased that replaces the 18 tailshaft with one that accomodates either a 6 or 10 spline input gear.

if you want to do it,my advice would be to find a post 53 spicer 18,with 1.25 inch intermediates shaft,and purchase the kit for whatever internal spline happens to be on the case you get. most likely it will be 6,so youll then be able to use this kit to mount an 18,or a dana 20 to your th400.

other ques?


------------------
scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

T18/dana-spicer 18 with drum E brake and PTO, swap very soon
widetrac offset dana 44s with clearanced center sections and rear discs very soon
BIG tow truck PTO winch and full roll cage install shortly thereafter
4.0 aquired-4.5L stroker someday...

now we can do some 'wheelin!
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  #11  
Old 04-22-2001, 09:31 AM
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Rande Rande is offline
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So, it seems to me that if you have to go to the expense and trouble of an adapter and output shaft, wouldn't he be better off going with a Dana 300? If you want to avoid the high cost of the aftermarket adapter, how about finding a T-400 with a Dana 20? The low range won't be quite as low but do you need that extra little bit when you consider the cost and work involved?
Should be able to locate a T-400-D20 combo for far less than the cost of the D18 adapter. D20 is also stronger than the D18. D300 is comparable in strength to the D20, just a bit lower in low-range.
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  #12  
Old 04-22-2001, 01:26 PM
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scotty scotty is offline
 
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even easier to find would be a 727 or 904,then a d300 will bolt right to it. due to the extra width of a 727,the 300 will have to be clocked slightly different,or a minumum of 4 inches of suspension lift will be needed for the frond driveshaft to clear the pan. a 904 can be built to handle v8 power,and is skinner,with no clearance prollems with front shaft. a factory 904/d300 could be found from an 80-86 cj prolly easier than an early th400/d20.

somethin else to consider,anyway the only downfall to a d300 is no pto available. to most people,this is not such a big deal,tho.

------------------
scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

T18/dana-spicer 18 with drum E brake and PTO, swap very soon
widetrac offset dana 44s with clearanced center sections and rear discs very soon
BIG tow truck PTO winch and full roll cage install shortly thereafter
4.0 aquired-4.5L stroker someday...

now we can do some 'wheelin!
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