View Full Version : Fj40 drive shaft lengths
01-29-2013, 10:50 AM
As you know I recently did the swap with a lot of help from the hard hitting mo'deckers here at rising sun. Pretty much got all the little details finished but I have hit a snag.
I thought I had bought (3) 4 speed pinion flanges and 4 speed drive shafts. The rear ds install went flawless, the front is another story. After we replaced the pinion flange on the output shaft of the tc, we noticed it didn't mate to the ds. The front diff mated up just fine btw. So we decided to slip the 3 speed yoke (smaller end) off the original ds and just put it in place until the new pinion flange came in from cruiser outfitters. Now the 3/4 speed ds mix was too short for a permanent fix due to 1.5'' if the splines showing on the ds. When the new pinion flange arrived I started to install that and noticed the "4 speed" yoke for the front was about the same size as the 3 speed. So I slipped it on and the same amount of splines are showing. App. 1-1.5 inches I guess. That seems wrong to me, right? Did I get a bogus front DS or since this is a 4 speed tranny and 3 speed tcase do I require a custom front ds? I am gonna pull the original 3 speed ds's out today and measure them but I feel a little stumped. so just for review:
4 speed tranny-3 speed tcase
Stock height for now but installing a 2.5 inch soon
Anyone have any ideas?
01-29-2013, 02:02 PM
1" to 1.5" of spline showingmay be OK. You need some spline showing so when the suspension compresses the drive shaft doesn't bind up and break something. Conversely, you want to make sure that when the suspension is at full droop the the 2 parts of the DS dont disengage and fall apart.
01-29-2013, 02:58 PM
Ok, the rear shows nothing and with the correct flange up front on the tcase has about 1'' showing. As of 240 pm today there is now all 4 speed parts, to the best of my knowledge.
01-30-2013, 11:31 PM
When I did my 4 speed swap on my 71, I just had my original driveshafts retubed at Englewood Driveshaft, so the yokes and flanges stayed the same. Based on what I knew at the time about the different companion flanges and the issues in matching them (see last paragraph), I figured this would be the least brain damage, and indeed this was a very smooth part of the tranny conversion.
4 speed yokes are bigger than 3 speed yokes and the u-joints are different. The 3-speed yokes retain the u-joints with circlips, the 4 speed u-joint races just press in.
To top it all off, there are about 3-4 different companion flanges (and mating yokes) used on our older Land Cruisers (and mini trucks and 4runners, some of which will interchange). There was an excellent article by Rob Mullen in Toyota Trails in the late 1990s which showed all those different companion flanges, with measurements and month/year of production identifying which was used when and on what kind of Toyota.
02-01-2013, 01:02 AM
...There was an excellent article by Rob Mullen in Toyota Trails in the late 1990s which showed all those different companion flanges, with measurements and month/year of production identifying which was used when and on what kind of Toyota.
02-01-2013, 08:55 AM
Guys, he apparently has flanges that match on all ends as the DS's are bolted into place and functional. His question is how to determine if the shaft lengths are correct and whether he needs longer or shorter DS's.
Look at a stock rig and determine how much spline is showing on the slip joint. My guess is the 1" to 1.5" is probably about right. Put tape on the shaft right where the 2 ends meet up on the splines. Then pull the shaft apart and measure how much spline you have on the inside. That will give a rough idea of whether you are centered up or too deep/shallow.
02-01-2013, 08:56 AM
The actual length of the flange doesn't change right? From front to rear?
So my next question is do you guys think when I install my lift things will "balance out?" My rear springs getting pretty old and tired.
02-01-2013, 09:05 AM
The actual length of the flange doesn't change right? From front to back...
Correct, negligible variance from flange to flange
02-01-2013, 03:45 PM
After we replaced the pinion flange on the output shaft of the tc, we noticed it didn't mate to the ds.
Guys, he apparently has flanges that match on all ends as the DS's are bolted into place and functional.
Seems to not be so apparent? What I am reading is that he had to use the 3-speed DS end at the TC front output to make it fit. In order to get the proper length on the TC end of the front DS, he need the proper companion flange on the TC to use the 4 speed DS end.
As it stands, it sounds like insufficient spline engagement on that front shaft, which might cause it to separate at full droop. We had a guy with a SOA 60 when I first joined the club who used to lose his DS almost every time we went wheeling, we used to rib him about it...
02-01-2013, 04:17 PM
Front Range Drivelines- (303) 783-9954. They do great work & seem to be affordable
02-01-2013, 04:40 PM
If you are going to add a lift, then definitely wait to adjust any drive shafts lengths until after that is done. Just make sure you have the right yokes and flanges available for both DS's. Once the lift is in, the drive shaft place will tell you where to measure from in order for them to make shafts the right length.
How big is your lift? Back when I did a 4" lift on my 40 I had to lengthen the rear shaft. Then I discovered it put so much angle on the pinion I had to rotate the diff up and re-weld the spring pads. That caused a vibration which required adding a CV joint to the top of the driveshaft.
Southside driveshaft experts:
Bill's Englewood Driveshaft
"You Can't Beat My Shaft!"
3364 1/2 S. Broadway
Englewood, CO 80113
02-01-2013, 10:04 PM
Only doing a 2.5 mainly to allow for the 33's and replace the old sagging suspension.
At Jeff: we just used the 3 spd ds yoke on the front just to connect the ds temporally. Then I ordered the correct flange from cruiser outfitters and installed it. Now my driveline minus the transfercase is all 4 speed.
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