GC-3 Chassis trick reducing torque twist

[Getrag]

Hey so as I had continued to struggle with torque twist I kept searching and came across the best thread on the forums that I have read so far:

Anti Squat and Suspension Tech

I learned a TON from this thread about torque twist. I initially thought that when I installed my GC-3 chassis that due to a 4 link setup it would magically eliminate the torque twist. I was wrong, it was horrible if not worse than it was from stock. After reading the above thread and deciding to alter the geometry of the 4 bar link I came across a simple way to use all the parts from the GC-3 chassis to minimize the twist.





I wanted to take the "formerly known as lower links" that the GC-3 uses for upper links and move them to the top of the rear mounting plate for better link geometry. Unfortunately they didn't really fit that way. So here is what I did:

I used the chassis pins that came with the GC-3 kit (these are the pins that are used to screw the chassis halves together) as the new rear upper links. I was able to use the stock mounting holes on the rear plate just by flipping the plate around. Unfortunately I'm only able to screw the mounting plate to 2 of the 3 holes on the axle housing but I'm not concerned about that.







I was only able to do limited testing where I put the crawler against a step and did a straight head on approach. but the rear left shock only compressed about 1mm!!! which is way better than before. I'll do some better testing tomorrow and mess with the geometry a bit more and report my findings. But this is a good start to those with a GC-3 chassis that still have torque twist issues and want to do a nice clean fix.

[thomass14]

Do you think you should lenghten the upper links to pitch the axle up so the driveshaft is at a better angle and not catch on the rocks?

[Getrag]

Originally Posted by thomass14

Do you think you should lenghten the upper links to pitch the axle up so the driveshaft is at a better angle and not catch on the rocks?

Yeah exactly. I don't have much hardware on hand so I didn't have any washers to lengthen it. My plan is to grab some tonight since the m3 set screws I used in the rod ends are 12mm long I should have some room to put a couple washers on each side to lengthen it. I don't like the angle on the drive shaft either.

I'm also going to grab some longer M3 screws that are used to mount the link to the plate so that I can shim the link up some more to see if that even further reduces the twist.

This also reduces some of the issues that people have with the lower and upper links hitting each other under articulation. Since the upper link is higher it gives me more clearance so the upper and lowers to hit

[Just crawl it]

Going to follow this thread thanks lovin all the great pics

[Getrag]

Ok did some small scale testing on my dinky pile of rocks at home and I have been able to tell a huge difference. The front right wheel doesn't pick up anymore!!

I lengthened the links with washers to get a better angle on the drive shaft





Also put a nut underneath where the links are mounted on the rear plate. I'll find out tomorrow if I see further changes.
The screws are a bit long since I'm going to keep shimming up the mounts to see how it changes performance.




Keep in mind if your trying this with your setup that link lengthening as well as how high up you mount them on the axle side may give slightly different results from mine, since removing torque twist by means of link geometry depends on other factors such as your center of gravity.

But this is a good way to start and keep trying different heights when mounting on the rear axle side so that you find whats optimal for your setup.

[Snipervision]

I can't wait to hear about your results. Would be great to take a pic of before & after or even a movie crawling on the same spot to see the difference.

[Getrag]

Originally Posted by Snipervision

I can't wait to hear about your results. Would be great to take a pic of before & after or even a movie crawling on the same spot to see the difference.

I'll try to get a vid next time, Unfortunately I was crawling solo so It would've been difficult. As for the results I really loved that there was almost no torque twist, however someone mentioned before (and I'm not sure why the post was deleted) that the shortened lengths can make it roll back easier in general.

I was trying to pay close attention to it. so now im going to bend the longer links so that they clear the mounting plate and i'll mount them toward the rear and on top to see if there is a difference, but so far just the above mods have worked to drastically reduce the torque twist

[RickM]

I think I tried posting this earlier before the huge outage but here goes again. I think the link length of this chassis is one of the reasons it tends to climb so well. Someone actually posted a great diagram of how link length and the relationship between the top and bottom links effects the forces of the traction of the tire on the ground, basically calling it wheel lift. Anyway I think it all comes down to how to get rid of as much TT as possible without impacting performance. I have found with a shafty some TT is just a part of it.

[Getrag]

Someone actually posted a great diagram of how link length and the relationship between the top and bottom links effects the forces of the traction of the tire on the ground

I've tried searching for that thread and can't seem to find it. I'd love to learn about that. In the mean time I'll try to use longer links and mount them higher up to try and get the best of both worlds

[RickM]

I dug around a bit and tried to find it as well and could not. It was so helpful for me that it should have been a sticky. Basically here is the gist of it. A wheel turning is going to give some upward bite as well as forward bite. If you can reduce the upward bite you get better traction/better climbing ability. TT up front can offset the benefits of the rear though. Here is what I would suggest if it were my truck. Try going back to the factory link lengths. Mount them as low as possible on the chassis. Try mounting them on the top side of the rear Plate to get them horizontal with the ground. The rear link mount spacing should be good enough. Your shocks if they are the stock shocks need to go away if you have the funding to do so. Get some of the duratrax shocks intended for that rig with a set of mini-t springs, or run a set of losi comp shocks. I am running the softest silver springs up front and the blue springs out back. I run the compression setting on the spring much tighter on the left rear than the right, and I run I think about 30 weight on the left and 80 on the right. That keeps bite on the ground and gets me a reasonable amount of managable TT. Hope this helps some. As far as the diagram goes, immagine how the links of different length twist the axle under load as a result of the movement of the axle to the chassis. Now immagine the axle compression with links the same length. When the wheel exhibits forward bite and unwanted upward force, it has less to push against with a longer link thus applying the energy more in a forward rather than upward motion.

OK found it. Take a look at this read. The picture I was refering to is a diagram on page two of this thread. It is not so much dealing with TT but now a new concept is gonna get tossed in. Anti Squat
Anti Squat and Suspension Tech

[Getrag]

Originally Posted by RickM

OK found it. Take a look at this read. The picture I was refering to is a diagram on page two of this thread. It is not so much dealing with TT but now a new concept is gonna get tossed in. Anti Squat
Anti Squat and Suspension Tech

Ok, yeah that is the thread that I actually have linked at the top of the page.
I have only made it through about 20 pages of that thread so maybe I haven't arrived at the link lenghth part, or maybe with the flood of info on there I missed it.

Either way I took your advice and took the stock links and mounted them on top of the mounting plate. Notice that I had to bend them to get the clearance I needed. I also have some nuts to shim them up a bit.
I haven't had a chance to test it yet. I'm going to go do some crawling at lunch tomorrow so I'll let you know how it goes. I did notice with the shorter links that it was more prone to rotating the entire front end over. I'm excited to see if the longer links changes things or not.

I also had to outboard the shocks on the axle side since the longer links were hitting the shocks pretty bad. (something I wanted to try anyway) It seems to be more steady and the body is less "floppy" if you will.

I'll post the results tomorrow when I test it out. Thanks again for the suggestion of the longer links

[jereosbou]

did you ever run your gc3 in the stock configuration without the bent links? and if so did you have a torque twist problem then. the reason i ask is i picked one up the other day and have had no torque twist using straight stock liength arms.
the uppers are mounted in the same hole you are in the last pic but under the axle plate. then on the chassis side the rear is the lowest hole and the front is up on hole. i have zero torque twist i mena zero. and im running a 7600 kv brushless inrunner on 3 cell. the motor is somewhat over kill i know and i rarely let it run full throttle but it is very torquey and still no torque twist and no lifitng one wheel on climbs. oh and vendetta shocks on mine that are outboarded.
im just wondering if the reason your torque twist started wasnt the bending and inherent shortening of the rear links on yours.
but then again maybe i just got lucky lol.

[RickM]

I found that the stock setup of a GC3 did give me tt that would lift the front wheel which might have been helped by squat. I went with a slightly firmer front spring setup and it helped plant the front. I ran a gc3 and liked it but had two rigs and kept the mini wedge which came with shorter rear upper links. Many wedge owners have been going back to the longer links with much better climbing results.

I still think the adjustability of the stock shocks will only make dialing out TT harder. So getrag. Those shocks gotta go!!

[Getrag]

I still think the adjustability of the stock shocks will only make dialing out TT harder. So getrag. Those shocks gotta go!!

HAHA I know... I know... I actually might pick some up today.

As for TT with the original GC-3 setup, I was still getting it pretty bad. In fact bad enough that I was sort of regretting forking out the money for the GC-3 when I so no improvement over stock. Although I am pleased with it now that I have been able to reduce the twist.

[hoyt]

This has been a nice informative thread so far. I ran the GC3 chassis all last year and must say I didnt notice any torque twist what so ever with the stock set up. I just switched to a wedge chasis this year (the version with the new rear axle plate to run the longer links up top) and am really loving it so far with just the couple runs i have on it. I have noticed a minimal amount of torque twist on it though. I think im gonna try and mount the upper links on top of the rear axle plate and see if it takes the rest away. Right now they are mounted under the plate. Keep the info coming.

[RickM]

A d-link(ax-10) type setup for the rear of these rigs would be sweet. I vuess that is what the pro plate does.

[neiloid1]

Originally Posted by hoyt

This has been a nice informative thread so far. I ran the GC3 chassis all last year and must say I didnt notice any torque twist what so ever with the stock set up. I just switched to a wedge chasis this year (the version with the new rear axle plate to run the longer links up top) and am really loving it so far with just the couple runs i have on it. I have noticed a minimal amount of torque twist on it though. I think im gonna try and mount the upper links on top of the rear axle plate and see if it takes the rest away. Right now they are mounted under the plate. Keep the info coming.

So you are running your rear upper links to the bottom of the rear plate? I'm still running short links on the rear with a pen spring in the rear right shock and get no noticable TT. Reckon it would be worth picking op the new rear plate when I order my Dub topper.

[Getrag]

So you are running your rear upper links to the bottom of the rear plate? I'm still running short links on the rear with a pen spring in the rear right shock and get no noticable TT. Reckon it would be worth picking op the new rear plate when I order my Dub topper.

Looks great. Thats effectively what I have now done with the GC-3 Only difference is since the GC-3 rear plate doesn't have those cut-aways on the sides I had to bend the links to clear the plate.

And by the way I took it out this afternoon to a park and did some small testing and I did notice a difference between the longer and shorter links. With the longer links it doesn't feel like it wants to rotate backwards as easily. A few line that I had a hard time with before I was able to get up this time.

[hoyt]

Originally Posted by neiloid1

So you are running your rear upper links to the bottom of the rear plate? I'm still running short links on the rear with a pen spring in the rear right shock and get no noticable TT. Reckon it would be worth picking op the new rear plate when I order my Dub topper.

Yes rear upper on bottom, after seeing the pic I dont remember exactly why I did it. Moving them should hopefully eliminate the slight t twist i have. You might as well get the rear plate, you would most likely not need the pen spring anymore.

[hoyt]

Originally Posted by Getrag

Looks great. Thats effectively what I have now done with the GC-3 Only difference is since the GC-3 rear plate doesn't have those cut-aways on the sides I had to bend the links to clear the plate.

And by the way I took it out this afternoon to a park and did some small testing and I did notice a difference between the longer and shorter links. With the longer links it doesn't feel like it wants to rotate backwards as easily. A few line that I had a hard time with before I was able to get up this time.

Nice, glad you got it worked out. Are you running any weight in the front?