driveshaft options
 

Ok Im putting a LQ4/4L80e into my 74 stepside shirt bed. I'm using 1" motor mount adapters. truck had a TH375 in it(TH400 with a long tail that uses a TH350 slip yoke). I know I'm at least going to have to change yokes but my question is should I get the driveshaft out of the silverado 2500hd that the transmission came out of or try to have a new yoke on my driveshaft? I'm pretty sure I'm going to need a longer driveshaft than what I have but not sure of exact measurements yet. I just wanna know which driveshaft I should work with because I may get a deal on the driveshaft when I go to get the trans next week if I get them together. Any help would be greatly appreciated.

Re: driveshaft options
 

I would pick up the driveshaft from the donor truck. At least that way you have two driveshafts to work with. The one from my donor fit with a change of the rear u joint.

Re: driveshaft options
 

I've always had a new shaft made. 'round these parts a thickwall steel DS with whatever end you need, built/balanced 800hp capable for under $350, iirc mine was under $250.

Re: driveshaft options
 

Same setup here and I had one made also. 280 with spicer joints. And it was done in 3 hours. All I dropped off to them was the measurements and the yoke.

Re: driveshaft options
 

+1 on getting a custom ds built. Not that expensive and it fits.


I used Driveline specialist of Texas due to not having anyone around me that could build one. Good folks

Re: driveshaft options
 

what was your setup and what vehicle did you get your driveshaft from?

Re: driveshaft options
 

if i cant make one or the other work then I guess ill have to go that route. Im on a tight budget though

Re: driveshaft options
 

Mine came from an 07 suburban. With ECE mounts and the 4l60e it bolted up with a rear u joint change.

Re: driveshaft options
 

Thanks bro. I think I need to find someone who has the 4l80 and see if they'll take some measurements for me.
Any volunteers?

Re: driveshaft options
 

For your own good, NO.

Measuring DS length is something you HAVE to do yourself for two reasons.
1. there are too many small factors for us to give you an accurate ballpark based on what factors are known. Where exactly your engine mounts in the cradle alone can create a large disparity in DS sizing.

2. when/if you have any future issues with pinion, vibrations, slip yolk issues or any other DS related problem; you'll already have half the skills to troubleshoot it yourself.

For example; if you put the motor in, use our measurements from an existing swap, then find out you need a DRASTIC change in pinion angle...well shoot we just wasted your time and money with our measurements, since now you might bee too long or too short for the correct fit. Getting reference measurements from the forum is totally fine, and in most cases I'm all for it (especially when distance or weather prevent access to the truck)...but unfortunately DS length is something gotta tackle yourself. (that diy list includes DS length, pinion angle, backspacing, and ride height on a particular suspension)

Re: driveshaft options
 

Here goes...with the truck on the ground , with all the weight on it (or on stands, with proper weight bias)...make sure it has the same rake, as on the ground? Bolt a u-joint to the pinion yolk, & use the proper trans yolk, with u -joint pressed in. Shove the yolk all the way to the bottom in the trans, mark with a 'sharpie"....then pull it back 3/4" min, to 1" max & make another reference mark. At this point, you can measure center to center on the caps & have the shaft built. This is the only way it will be "right on", as other guys have stated, there just are to many variables, on engine placement/trans lengths,ect ;) Longhorn

Re: driveshaft options
 

sorry i didnt elaborate. I wanted someones measurement simply as a guideline to decide whether my driveshaft was going to be too short, not as an exact measurement.If mine is too short then I was going to get another driveshaft to start with. Thanks for explaining how to figure out the exact measurements that ill need though, I'll definately do that once I get everything set in.;)

Re: driveshaft options
 

no volunteers? :(

Re: driveshaft options
 

Even if another member running the same gen truck and the same trans DID take measurements, the variable we mentioned still apply. Those 1-3" of difference are enough to make-or-break the fitment...so it wouldn't actually help you.

I don't know how long a donor 2500hd driveshaft is, nor do I know what your stock driveshaft length is. But the best I can do is tell you this; the internet says a 4l80e is ~26.25" long. An LS motor is about 1.25" shorter than a small block. You could tape measure some generic line of sight measurements and ballpark the difference....but at that point why wouldn't you just measure the right way?

Re: driveshaft options
 

Because the drivetrain isn't in the truck, I have yet to purchase the transmission, and I'm simply trying to figure out if I should work up a deal for the driveshaft when I buy the trans. I'm not buying the trans till everything else is ready because the yards only offer a 30 day warranty on them do when I DO buy the trans, I don't want to have to be searching for parts or waiting on a one off custom job. I want to be able to hurry and get it in and make sure it's functioning properly. I can have a driveshaft shortened and re welded in a couple hours just to check function and if need be, get a custom driveshaft made later. I'm simply planning ahead. I fully understand and accept that the final product will be individual and specific to my vehicle. Again, I'm only asking for a rough initial estimate from someone with a similar setup.

Re: driveshaft options
 

4L80E's vary in length, 31 3/4", 32 3/4" & 33", The 33" versions are Roller Output with a parking brake, The 32 3/4" is the one you want (It accepts a Slip Yoke), 31 3/4" is the standard Bolt-On yoke version. (These are lengths I got online)

Does your TH375 have a 9" extension housing? If so, The trans will be roughly 33 1/2" long (Online reference)

As others stated, You need to measure the driveshaft length when you get the Engine & trans mounted, Otherwise we are all shooting in the dark!

It won't take 30 days to get a DS built..3 days tops. It only takes a few hours to test a trans thoroughly.

Wreaking yards are SCUM, Check out the unit before installing it! Fluid condition & debris amount it the pan tells you a lot about an auto transmission. If that checks out, Throw it in & run the crap out of it!

4L80E's are stout units, However most of them get worked HARD, It is not unusual for them to be worn pretty good at 150K if they were pulling trailer all their life, On the other hand they are 400K mile units if not worked hard.

Re: driveshaft options
 

You're absolutely correct! I just measured the th375 at a hair over 33 1/2. Also, my driveshaft has NO movement! I had to pop the caps off the ujoints, jack the transmission up, and pry the uncapped ujoint out if the pinion yoke with a pry bar to get it out so depending on which 4L80 I get, and where these offset motor mounts place the engine, I may get away with just changing my trans yoke, at least temporarily.
Just so I know what to look for, do you have any idea which vehicles came with the 32 3/4 version that I need?
And thanks for the advice! Ive been googling all day trying to figure this stuff out!

Re: driveshaft options
 

I've found the most 2wd 4l80e (all variety) in service vans from cable companies, plumbers etc.

Re: driveshaft options
 

There are several of those on Craigslist in my area but they are from 98 or 99 models with sbc engines. Can I use those older, non-LS transmissions? Because some I'm seeing are in the 300-400 range with 100k or less in them but trying to find a 2000 or up unit doubles or even triples the price.

Again, thanks for all the help gentlemen.

Re: driveshaft options
 

Also, I was reading a thread on ls1tech last night saying that a slip yoke can still be used, even on the 4l80s that came with bolt on yokes. Denny's driveshaft makes the yoke that works with them for only $59. They were also saying that from 94-up, the only external difference in the 4l80 is the extra bell housing bolt hole at 12 o'clock and that the LQ engines come with a special flexate that already has a spacer to use older style transmissions so I went to the garage and looked at my flex plate and low and behold, it has what looks like about a half inch thick ring welded to the center right where the converter snout would be so I'm thinking that's the spacer but I wanna be sure before I drop any cash.

Re: driveshaft options
 

Mines like a 97 or 98, and didn't require anything special to run behind the LQ. The flexplate spacing should be fine if your starting with an LQ4/9. If you went with the smaller motors, then the spacer comes into play. Your flexplate should have the right clearances for any year 80e.

Re: driveshaft options
 

THANK YOU SIR!!!!!!!!! you just brightened my whole day and saved me a couple hundred bucks as well!

Re: driveshaft options
 

just tell your harness person that what year it is. I'm pretty sure the wiring was the same, but if you go far enough back (like 94?) the internal harness was different (but can be changed with a little effort).

Re: driveshaft options
 

I found a guy parting out a 99 service van wanting $300 for transmission but it's got almost 200k on it. Found a few more options for less than $500 also on Craigslist if I'm willing to drive a couple hours. Waaaaay cheaper than the $700-1100 prices for the 2000-up transmissions that I was looking at. I even found a rebuilt one out of a 97 Silverado 2500 with less than 10k and a warranty for $625! Might be looking at that one this weekend and doing some haggling.

Re: driveshaft options
 

I had to do a drive shaft for my 76 4.8l 4l60e, I bought a used 2002 1500 aluminum shaft out of a standard cab short bed (that what LKQ told me). I took my measurements and went to a drive line shop.

The part that took the most calculation was figuring out the correct conversion joint to mate the new drive line to the old differential pinion flange. I figured I saved about $100.