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4L80E crossmember


PhatNBad

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  • 4 weeks later...

Sorry that no one has replied. I will be doing the same swap in the future but not for another year. From what I have gathered so far the stock crossmember can be used by cutting of he mounting tab from the front and switching to the rear. You will probably need to slide the crossmember back also. If it doesn't match up with existing holes in the frame then new ones will need to be drilled. The mounting tab will need to be welded back on. Make sure to keep the 4l80e on the same height as the old set up to maintain the proper drive shaft geometry. Easiest way to do this is to use an angle finder at the back of the transmission. You should be able to download an app for your phone. As a last note make sure that your engine and transmission mounts are in good shape while making measurements, both old and new transmissions. This can throw of the angles and drive shaft vibrations aren't fun.

   

Edited by zmanabba
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14 hours ago, zmanabba said:

Sorry that no one has replied. I will be doing the same swap in the future but not for another year. From what I have gathered so far the stock crossmember can be used by cutting of he mounting tab from the front and switching to the rear. You will probably need to slide the crossmember back also. If it doesn't match up with existing holes in the frame then new ones will need to be drilled. The mounting tab will need to be welded back on. Make sure to keep the 4l80e on the same height as the old set up to maintain the proper drive shaft geometry. Easiest way to do this is to use an angle finder at the back of the transmission. You should be able to download an app for your phone. As a last note make sure that your engine and transmission mounts are in good shape while making measurements, both old and new transmissions. This can throw of the angles and drive shaft vibrations aren't fun.

   

Thanks for the reply.  I did hear that before about cutting the mounting tab off the front of the factory xmember, flipping it over and welding it to the backside.  I do have a question in my head about it.  Would the new location for the tab be in the same exact spot (height) as when it was on the front, except on the back of the xmember?  I guess what I mean is the mounting point on the 4L80E at the same height as the turbo 350 (to keep the pinion angle the same)?    

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The important part is retain the same angle. Unfortunately I haven't done the swap yet on mine but I have done a few other cars. From what I have found out there is ample tunnel clearance so moving things around to get the proper angle won't be a problem 

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  • 11 months later...

I should have searched this out before but I just bought a trans crossmember from G- Force to fit my TCI 6X conversion ( 4l80 ).  Should be here 1/20 so will provide info here if it works or not.

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I'm putting a 4L85E in my 72. Look at the below link and a few more posts down from that to see what I ended up doing. Maybe it'll give you some ideas or stuff to look at.

 

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Since I'm selling the small block and th2004r together, I'm looking for a good overdrive replacement. I see Hot Rod Magazine just did a 4L80 rebuild. I'm thinking of going that route for my 427 BBC.post-259-0-61935100-1474727657_thumb.jpg

Edited by 420ponies
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Nice job with the cross member mods.  I looked at mine and figured it would require tubing mods as I didn't have room to move it 8 inches back from where it was for my 4l60.  Hopefully the g force one will work properly.

 

Do you have any info on what mods you did to make your 4l85 fit the tunnel?  I'm looking at making an fittings with elbows to connect an trans cooling lines.  Might have to make some dimples in the tunnel for them still.  Have definite issues with the speed sensor connection.  Trans is at 5° so tough to leave it at that angle.  Without adding some height where the tail shaft mounts to the body of the teams, I will only gain 3/8 of an inch until that part hits the tunnel.

What have you found in your installation effort?

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Thanks Kevin.

As far as tunnel mods, I had to 'massage' the tunnel a bit near the back of the trans to clear the tailstock. No cutting was necessary, also a bit where the sensors are located on the sides. For the cooler lines, get the banjo adapters. Keep in mind, there are 2 sizes. Read the ebay description below & decide which ones you need. I had the thread pitch as mentioned in the link.

https://www.ebay.com/itm/6AN-x-9-16-18-4L80E-GM-transmission-oil-cooler-90-degree-Banjo-fittings-USA/232704702481?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

In my measurements, the G-Force would have dropped the trans even lower than the stock one. That's why I made the decision to just mod the stock one. No sense in spending $300, and then shimming the crap out of it to raise the trans back up.

The chart I looked at shows the trans mounting pad to be 4 1/4" different on the 4l60 vs the 4l80 from the bellhousing, so I'm not sure how you figured 8" difference. My crossmember bolts to the rear most set of holes in the frame, but definitely fits. One question now that I think of it....do you have a older style engine or is it a LS conversion? That may be the difference & the engine sits back further?

What shifter will you be using? I had to mod the factory floor shift base plate a bit after moving the floor up for clearance. It wouldn't bolt down properly as it sort of followed the floor contour in the middle. I got another one and notched it out, reinforced it afterwards and all is good, bolts up perfect in the original location. Using a Shiftworks K100-32 cable to actuate the gear selector as well.

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Holy smoke!  Did this response up this morning but didn't hit submit before getting distracted and forgetting.  Was looking forward to a reply but can't get one if ya don't send it silly!  I contacted the folks that make the banjo fittings and have determined I do have the 1/4" ones so will order them up....likely get 2, just in case.

I searched for Banjo fittings but didn't seem to be getting anywhere but also didn't search ebay specifically.  I think Banjo fittings will be the best option  so will order a set of those vs cutting and tapping the regular fitting to install an elbow.  I was worried they were just going to be the regular fitting but the fact they made them with the extended part for the rear one is fantastic.  I have the fittings spread apart so they should be the 1/4 NPSM fittings.  Shame it may take up to a month to get to me according to them but extremely gratefull that they make them so I'll live with it.

I am installing a TCI 6X behind a Mark 4 BBC.  Supposedly the TCI 6X is the same case as the 4l80 but don't have one to check measurements myself.  My measurements come from the 4l60 I removed where the rear mount is 22 1/2" back from the face of the trans and the mount on the TCI 6X I'm installing is 30 3/8".  For confirmation sake give yours a measure and let us know what you find.  I started this because I thought these trans were not that different and should be an easy swap but that extra length is a complicating factor.  On the TCI website, among others, the mount position is only 26" but that is wrong.  The mount is at the back of the tailshaft not the back of the body so the body and mount numbers are reversed.  Spoke with TCI tech and got him to measure it with his Mgr and they came up with 31" (?) and will supposedly change it on their site.  I only had 4 1/4" left to move the rubber and metal cap system to the rear bolt holes so even removing that system and mounting it to the frame directly still wouldn't have been enough so started looking for solutions and came up with the G force one.  Found it on Summit and they had it in stock so got it ordered.  The TCI one they make wasn't even made. They still said it would take 3 weeks to make it and get it sent out so I'm happy and hopefull the G force one was available right now and as I'm crossing my fingers, will fit right. 

I looked into the cable idea too late to get the shiftworks cable added to the G force order but that looks like a best solution to being able to continue to use the factory horseshoe shifter.  I already have it converted over to work a 4 speed so just need the 32" cable.  That factory cable just won't bend enough to get around the speed sensor and line up to mount the bracket correctly.  I almost think a shorter one would work better but don't want to buy the factory length 30", the 29" for the Corvette or the 27" cable and have them be too short so will go with the longer and decide later if I could have gone with a shorter one.  The 32" one is the one Shiftworks says works best to get around the speed sensor for a 4l80 install.

I was hoping to modify the floor for the tailstock and not affect the shifter.  Perhaps if I do it with it in place it will keep the mounting points the same while letting the floor move to clear the trans.  Will do the check twice, or several times, before getting into that.   The sensor and cooler lines shouldn't be a problem to move as there is nothing supported by it.

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9 hours ago, colonel said:

 

I am installing a TCI 6X behind a Mark 4 BBC.  Supposedly the TCI 6X is the same case as the 4l80 but don't have one to check measurements myself.  My measurements come from the 4l60 I removed where the rear mount is 22 1/2" back from the face of the trans and the mount on the TCI 6X I'm installing is 30 3/8".  For confirmation sake give yours a measure and let us know what you find. 

I just got out of work and measured my 4L85E. It is roughly 30 3/8 from the bellhousing to the center of the mounting pad. My stock T400 crossmember works fine (with the mounting pad mod as in my thread). The mounting pad is also located at the rear most part of the tail stock, close to the rear seal. So, it seems like you have a standard 4l80 case, so it should bolt in as mine did. I also eliminated the rubber cushion end mounts on the crossmember and bolted it in solid, that may buy you a little more rearward room too.

Another thing that may help with floor clearance are urethane body mounts. Here is a series of articles that addressed putting a 4l85e in a Chevelle that I used as a sort of guide. Granted, I didn't end up using the G-Force part, but this series was still very helpful. They address the trans & mounts in a couple of different articles.

https://www.hemmings.com/blog/article/surgery-without-scars-1969-chevrolet-chevelle-2/

https://www.hemmings.com/blog/article/surgery-without-scars-almost/

https://www.hemmings.com/search-content/?q=Surgery+Without+Scars

https://www.google.com/search?rls=com.microsoft%3Aen-US%3AIE-ContextMenu&ei=EosoXf7vD4r0tAbNr7eYDw&q=Hemmings+Muscle+Machines+++Surgery+Without+Scars&oq=Hemmings+Muscle+Machines+++Surgery+Without+Scars&gs_l=psy-ab.3...5084.6952..7904...0.0..0.83.229.3......0....1..gws-wiz.r4D9TXXMAyY#spf=1579277509304

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Thanks for posting them.  Those articles are very helpfull.

Shame I am going to loose the x pipe.  Might loose it even if I use the original cross member becasue it is so far back.  That Chevelle tunnel seems to provide them a bit more clearance to get the 3 degree angle.  Mine is at 5 and hitting the speed sensor to do that.  Don't have to get it back to 3 as I'm using EFI and can easily adjust my diff angle as I have adjustable uppers on it.

They seem to be able to use the factory shifter cable as well.  Mine seems reluctant to bend that much and avoid the speed sensor.  Maybe lifting trans will help.  Have you tried that 32 inch Shiftworks cable yet for fitment?

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I saw that with the X-pipe as well, I'll cross that bridge down the road.

As far as the Chevelle tunnel.... I physically have the 4L85 in my car now (72 Custom) & it fits just fine with just a couple of whacks near the tailstock and where the speed sensors are. I did a little where the cooler lines are, but it probably wasn't necessary with the banjo fittings. Still not a bad idea while you're under there though. The poly body bushings helped a bunch I think too. Don't get the set listed for a 'Monte', get the 3.4170G and the supplement 3.4171G set from Energy Suspension. I did a lot of looking before I got those, plus spoke to their tech support engineers a couple of times. The 'Monte' sets are being superseded by the above numbers, and more complete he said.

I do have that shiftworks cable listed above & have it mocked up. I don't have an OEM cable because the prior owner had a B&M shifter with super long cable.  Keep in mind, I ordered it based on the Shiftworks website that suggested it for a 4L80 application. I tried routing it a few different ways and scrutinized the 32" cable a bunch and sort of thought a stock length one would work, but kept going back to the 32". So far, that's what I'm going to use. It snakes around the brackets and sensors but seems to operate real smooth.

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Got the g force cross member Monday and test fit it.  The mounting holes are exactly 53 5/8 on center.  My frame holes are 54 1/4 so I can bolt one side in and see the edge of the cross member support tab through the holes on the other side.  Missed it by that much!

I ordered the one for the 4l80 and the mounting tabs are higher than the one for the 700r4/4l60 which dramatically lowers it.  I still have almost and inch of space between the bracket and cross member with the 1 5/16 mount in there and I still need to move the trans up in the tunnel.  If the pictures on their site are correct it would seem the RCAE one would work better than the RCAE-4 for the 4l80 trans.

I picked up a 2 inch energy suspension mount and will look into modifying this cross member.  It mounts in the 2nd and 3rd holes from the back and is angled back from there to support the trans.  If I widen the exhaust areas and narrow the trans mounting area I might have enough room to work with to keep the x pipe exhaust system.

Once I finish clearancing the tunnel and get the trans positioned at the right angle I'll have a better idea how much space I have between the cross member and the mount.  Extending the exhaust areas will raise it a bit but if I need more I'll move the mounting tabs down to raise it up and minimize the spacers.  Widening the exhaust areas will also allow me to create a 54 1/4 distance I need between the mounting tab holes.

What is the center to center distance between your mounting holes in the frame rails?  If it isn't 53 5/8 I wonder where they come up with that number?

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My mounting hole distance is pretty much at the 53 5/8" number. Maybe your frame is bowed out a little at the center. Are the frame rails bent up along its length like someone put a floor jack in the wrong spots and bent it all up? Seems a lot of them are that way (mine was, had to straighten it).

As far as the trans being lower with the G-Force crossmember, that's exactly why I chose not to use it. Not sure if the RCAE they have will work either. Comparing the pictures they have on their website, the trans mounting tab is a lot further forward  compared to the 4l80 crossmember (which also has the arms at a steeper angle to push it back farther as well). I printed pictures of both and superimposed them, the differences are pretty clear.

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I can see those differences now that you mention it.  I was so focused on the height issue I didn't see the angle and mounting tab differences.  With the 4l80 you definitely need the increased angle the RCAE-4 gives you.

When I first found this cross member issue I debated about just making a custom one but couldn't do that without having the trans fitted properly and having the headers attached, which needed some mods anyway, and towing it back and forth to a shop so started looking for premade ones.  Didn't do as much research as you but with my distances between frame rails off, which I will look into when I get back there tomorrow, I would be customizing one anyway.  At least when I get the tunnel mods done I can measure things up to widen the exhaust areas, raise the trans mount tab to minimize the gap and do it without removing the car from the garage.

I can also see how the shifter is going to be affected by raising the tunnel to clear the tailstock so will be mindful of that when I get to that tomorrow.

Your experience has been a great help.  Thanks.

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You're very welcome Kevin. It's been a learning curve for me with this project as well. Find an issue, figure it out, make it happen and then off to fight the next fire. My next fight is wiring the car with a new harness, fuel injection, trans control, Dakota digital dash, stereo, alarm, etc....

There were a few times I had that crossmember you have in a shopping cart online with one button to push, but for whatever reason I didn't buy it. Glad I didn't. The main reason I think I stalled on it was it just seemed to hang too low at the main framework for no reason (the way it's fabricated where the exhaust hoops meet the cross bars and just hang low). I would have trimmed it down anyways as it seemed like from the side view, it's all you would see hanging below the car. Luckily the stock one worked with minimal mods and it tucks up there pretty nice.

Getting back to your 54 1/4" dimension, what crossmember was in there before that fit? You mentioned a 4l60 trans, but was there ever a stock crossmember in there at some point while you owned the car? Or, was the issue masked because of the rubber sleeve cushions it sat in on the ends vs. bolted in solid to the frame.

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On 1/23/2020 at 5:24 AM, jft69z said:

 

Finally made it back to the garage today.  Lower frame rail in trans cross member mounting area is 50 7/8 all the way along.  No visible twists bends or other damage I can see that would make my mounting holes 54 1/4 instead of 53 5/8.

The entire drive train was in a different 70 Monte and it all got swapped over when I got the 70 I have now.  It had the original trans cross member and I was able to get the rubber and metal clamp system in this cars frame so that is what I was using for the 4l60 and it worked great.  The other car I had to drill a hole in the frame and the cross member and just mounted it directly to the frame.  Couldn't seem to get it to fit in the other car but went in easy on this car.  Checked this cars body mounts and they look great.  Almost think that had been changed in the past as you can read Chevrolet in raised letters on them.  Somehow I doubt that was the way it came from the factory.

Will get the tunnel cleaned up and clearanced tomm then test fit things again once I get my trans pan back from having a temp bung welded in.  Once the tunnel is where I need it I can size things up for the mods to the cross member and get that going.

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