The Stovebolt Site Forums The Parking Lot Big Bolts Making my 69 Chevy Dump go faster

Hi i was wondering my chevy i think has a 4spd with a 2 spd rear, and it only wants top out at 30-35mph what could be causeing this. And how would i check the 2 spd rear. and is there a 5spd swap i can do to the truck to make it so it will reach 55 or so.

Sounds like your 2 spd is not working and are staying in low, or that thing has some serious off road gears.

can also look into a axililary trans,
spicer made 3 auxiliary transmissions for chevys according to the info packet for my 69
7231-a 3 speed .74
6041 4 speed .86
7041 4 speed .83

69chevdump,

What type 2 speed actuator do you have on the gearshift lever...electric (red button & wires), or a vacuum control with tubes etc?

Stuart

It is an electric one i believe. It is like just a button, i do not think its a vacuum controled.

SO how would i check the rear end. When i have the ignition on, and i play with the button i can hear it go in and out. or do something.

69chevdump,

Most 2 speed units would be Eaton. If you can move the button, and hear the unit shift, that is good AND bad.

It means the button is functional, the contact switch in the rear end is good, and the shift motor works...that only leaves the hard gears and linkage inside the differential, which would be bad news.

The entire two speed motor and switch can be easily pulled off the rear end, and either taken to a shop that works on medium duty trucks, or dinked with on the bench.

With this assembly removed from the truck, it exposes a small stub shaft with a slot in it. If you jack the rear of the truck up, you can actually shift the mechanism with a large screwdriver and prove that the guts are good.

The most common failure on these bullet proof Eaton's is a bum switch on the shifter, a bum limit switch in the rear end housing, or a bad motor. Any of these problems result in no noise or movement when the button if shifted.

There is a cover on the motor/switch assembly that is bolted to the rear end. If you remove the cover, you can see the limit switch, and with someone in the cab doing the shifting, you should hear the motor, and see the switch actuator move from one contact to the other.

If you actually hear the thing doing something, it sure sounds like it's working. The first thing I would do is verify the gear lube level in the differential, then jack up the rear end and play with the button as you run the truck....see if you can make it shift.

This unit is electric (if it's a Eaton), so don't overlook the fuse, it must have power.

Stuart

THanks stuart ofr your help, i dont know if this will help out or not but when im not driving and i mess with the button for the rear end, you can hear it work. when im driving i ussually keep it on high, but on the times when i would start out in the low side and would take my foot off the gas and ingage the high end, and put on the gas to go it wouldnt go, it was like free reving. like i had the clutch in. and then once i stoped it would be fine driving in the high end otf the 2 speed rear.

69chevdump,

It sounds like the 2 speed is fine, but maybe your shifting method is not allowing it to shift properly.

The shift motor winds a big spring up and loads the gear. When you relax tension on the drivetrain, it allows the spring to unwind and shove the gear into the selected position.

If you were to be in 4th under and pull the button UP to shift into hi-range, and you didn't back off on the throttle to slack the drivetrain, you could cruise forever with the spring wound and the unit just waiting to shift...you need to disengage the drivetrain momentarily for it to shift.

Play with it and we'll keep our fingers crossed.

Stuart

Thanks, well i mean my shifting is ok in the thing i think the tranny needs to be alil bit worked on, but with a 4spd what would it ussually go, speed wise?

Just to add a little extra, using the clutch when shifting the rear will help. Many shift it without the clutch, but using a clutch will insure a better shift. When upshifting, just pull up the button when desired, depress the clutch and let it shift. When downshifting, use the same method but with hitting the button just before depressing the clutch. When split shifting (lower gear to a higher gear on trans, high to low on the rear), shift the trans first then hit the button.

69chevydump,

If this rig is a '69, and it wasn't ordered with some extra low rear end ratio, then in 4th direct, I think it should be able to do at least 55 mph and maybe even 60 mph.

Stuart

My 64 with a SB 350 a SM420 a two speed rear and 10.00 22.5 tires will run 55 the RPM is a little higher than I would like, but I can still make short burst to 60 it is screaming as high as I will go at 60, it’s a good runner but the motor is still worn out.
I hope this helps. Are you sure you are getting all the RPM out of your motor if you are in high fourth it should certainly go faster than thirty five. Are you sure you are not going faster and the speedometer hasn’t shifted to read in high? Somewhere in the speedo cable there is a little two speed transmission that shifts to read the different gearing in the rear end check to see that it is working.

yeah, i drove her out to store and when i did my gf was behind me and she said the fastest i got up to was 40 going down hill. other then that it was 30 to 35.

If i wanted to put a 5sp tranny in, which one would i want to throw in.

Try this first to see how we can help you more.

Start off in 1st gear, low range (button down), shift thru all the gears. When in 4th and ready to shift again, just pull up the button, depress the clutch and see if it will shift. If it does not shift to a higher gear, then there is definitely something wrong with the rear.

OK i will try that tommorrow and see what happens. thanks

May be help, may not, but I just posted the shifting instructions that were on the visor of my old rig on the "split shifting" thread.

It does sound like what was going on with my truck though, it was stuck in low and had a blazing top speed of 38! Was just sticky, once I changed the lbe out & started using it it loosened up and shifts fine. just need to practice so I'm not grinding it so much!

lol thanks i will have to look into that.

Hey Bill, I did what you said. I went threw all the gears in low, and then clicked up into high. I heard the drive train drop down like it went into gear and it did. But it still whinned out at like 35 to 40 mph. Would it have anything to do with the transmission.? i hear the flywheel in the tranny rotating when im driving it?

40 mph, and you are sure you are on the high side of the rear, something sounds fishy.

Is there by chance an extra gear, and you just have not found it? It could be the shift rail for that position is rusted in neutral, so you can move the stick over there, but not move it into gear?

Is the engine running right? The timing set right, plug wires in the right places....

69chevdump,

If you have actually found the highest gear in the transmission, it would be a one to one ratio. The first step to discovering what is really happening would be to jack the rear end up and using the rotation of the tire and drive shaft, determine what your rear end ratio is. This would be the ratio when in HI range. Flip the button to LO while checking, just to see if it shifts to a different ratio.

Hi range figures should be the actual ring/pinion ration. Shifting the axle between the two ranges will verify that the unit works, and that HI range on the button is actually HI range in the rear end...wires haven't been crossed!

Is everything works properly, then several possibilities exist...you haven't found high gear in the transmission, the two speed isn't getting into HI, or the rear end is equipped with a very dramatic ratio.

Jack the rear off the ground and find out what happens where it counts...the rear end.

Stuart

Thanks Stuart,

When i drove it yesterday, i took off in all the low gears. When i got to the last gear whinneded out to and the engine was screaming, i pushed the clutch in, and i pulled the button up. When i let the clutch out, engine rpms drop tremonously like i want into 5th gear and it kept going. so i would imagine the rear end works. now what im starting to conclude is that instead of it being a 4spd it might actually be a 5spd but its not going into 5th gear. in a tranny like that would a 5 gear be over and up. so far its like this

1 3
R 2 4 wouldnt 5th be up.

if it is, it wont go in.

69chevdump.

I researched your type of rig a bit, and 5 speed boxes are pretty common. What the shift pattern is, I don't know, but I'll bet the one you diagrammed is right. If that's true, it sure sounds like 5th should be straight up from 4th, so something must be messed up inside the transmission. Time for Mr. Goodwrench.

Stuart

69chevdump,

I did a search in this forum using the term 'shift pattern' and found some interesting stuff. I have linked a page of patterns, but you need to know what box you have. Try that search and read some of the stuff...it's interesting.

http://www.chevyc60.com/the_transmission_page.htm

Stuart

At this point I would crawl under the truck give the transmission a good cleaning and do a search for a data plate or any identifying numbers write down all the info that you find and identify it.
If it turns out that you have a five speed pull the floorboard cover and remove the top of the transmission and inspect it for anything that may be obviously wrong.

69chevdump,

You have got some good advise so far, but right now I'd only do the checking work first, especially the trans info.

I looked back and don't believe we know what model series you have. Is it a C-60? Also do you know if it is a wide front axel truck or narrow? A quick way to tell is how wide your front fenders are. Do they flare out about 3 or 4 inches? or about 6 or 7 inches? Of course a picture would be great if you could post one.

The shift pattern that you posted, more like I would descibe as
0 1 3
R 2 4

(had to put the "0" in to make it work right)

is actually a SM 420 pattern (assuming for now it is a 4-Speed) and it don't sound like that would be the correct trans in your '69. If it is not original, needing to know the info on the trans would be helpful at this point.

Bill

Here are his pictures:
http://www.stovebolt.com/bboard/cgi-bin//ultimatebb.cgi?ubb=get_topic;f=27;t=001399;p=1#000000

Thanks Grigg,

Wide Axel!! Nice truck. I'm going to guess that the GVW is some where between 25,000 and 30,000. You never know for sure, but a heavy truck like that should have had a 5-Speed trans. Let us know the info when you find out.

Bill

Thanks bill and stuart and henery i appreciate all the help, well i have to get under there anyways because i think my starter went on me. SO now i will have to find one to put in before i try to do anymore work. What should i look for in a started? would that be like a regular c10 starter or a custom? yeah i dont think that something is right. It should go faster. thanks

Thanks, it needs some work. but if i keep it. then im going to do my restore on it.

stuart i looked on that site, none of those shift patterns are like mine. i dont know why?

If you have a good auto electric shop in town that rebuilds starters, I would just take it there and have it tested. They will then tell you what it needs and give you a price on fixing it. Sometimes it's just something minor or in-expensive.

ok i will have to do that. thanks.

69chevdump. I think you should sit in the truck and move the gear shift around and try to pin point the number of gears it has. It may be a 5-speed with a 4-speed shift knob. The shift pattern may be like this:
1 3 5
2 4 R

Another possibility would be:
1 3 5
R 2 4
I have also seen R 2 4 5
1 3
That is usually only seen in large trucks. I ran into it in a '79 Kenworth.

I once bought a John Deere bulldozer with what was supposed to be a 4-speed transmission. One day I accidentally discovered another position; forward and all the way over to the right. Slipped the shift lever over there and it must have tripled the speed of that dozer. Regardless of whether your truck has a four-speed or five-speed neither one would be an overdrive so the top speed would be the same with either type of transmission. Too bad the truck doesn't have a tachometer; you could probably solve the problem in a heartbeat by watching the engine rpms.

Jay 1124

Jay,

It has probally
1 3 5
R 2 4

But something is not letting it go into 5th gear. I dont know. But reverse is how you see it there.