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700r4 Cant find gear?!

A

Artemis Entreri

1/2 ton status
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Jan 3, 2008
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Staten Island, NY
Ok so I installed 3/4 ton stuff, 4.10 gears and 35in tires on my 91 k5.
350tbi, 700r4 trans.

And it felt fine driving it around town while I was taking it for little test drives while bleeding the brakes or straightening the wheels, stuff like that.

I took it on the highway for the first time today and it was horrible, every 2 seconds it was bumping and grinding, it wouldnt respond to me giving it gas, just heard and felt the trans jumping around under my foot, what I was assuming was trying to find the right gear?

Why is it having so much trouble? Did the new gears do this, or the bigger tires? Both?

What can I do to remedy this? Its undrivable at this point.

Help, please, lol.
-Steve-
 
Any chance it's the driveline? What did you do about the U-joints when you went from 1/2-ton to 3/4-ton? If you didn't use the adapter U-joint then that is responsible for the horrible noises.
 
I dont think its the driveline, its fine when im going around town, and if I feather, FEATHER the pedal, sometimes it wont clunk back and forth, but thats accelerating way too slow for highway speeds.

If I put my foot to the floor sometimes after a few seconds of clunking back and forth it will drive semi-normally again, it happens alot when going up inclines.

I didnt do anything about the driveshafts, the front is actually just a 8 lug 10bolt, and the reat is a 14bff, ujoints and driveshaft seemed to go together fine, I didnt know there was something I needed to add?????
 
Artemis Entreri said:
I dont think its the driveline, its fine when im going around town, and if I feather, FEATHER the pedal, sometimes it wont clunk back and forth, but thats accelerating way too slow for highway speeds.

If I put my foot to the floor sometimes after a few seconds of clunking back and forth it will drive semi-normally again, it happens alot when going up inclines.

I didnt do anything about the driveshafts, the front is actually just a 8 lug 10bolt, and the reat is a 14bff, ujoints and driveshaft seemed to go together fine, I didnt know there was something I needed to add?????
Click to expand...


Don't think the 14bolt FF has the same ujoint as the 10 bolt you replaced, you need a conversion joint like mentioned above.

I've never done it, but would think it wouldn't go back together with teh wrong joint in there......but who knows.
 
Artemis Entreri said:
I dont think its the driveline, its fine when im going around town, and if I feather, FEATHER the pedal, sometimes it wont clunk back and forth, but thats accelerating way too slow for highway speeds.

If I put my foot to the floor sometimes after a few seconds of clunking back and forth it will drive semi-normally again, it happens alot when going up inclines.

I didnt do anything about the driveshafts, the front is actually just a 8 lug 10bolt, and the reat is a 14bff, ujoints and driveshaft seemed to go together fine, I didnt know there was something I needed to add?????
Click to expand...

That is probably at least most of your problem. The stock 10 bolt axle uses a 1330 u-joint and the 14ff uses a 1350 u-joint. Correct this first then go from there. IIRC you need a Napa #447 u-joint.

Secondly, the 4.10 gears with 35's aren't helping you any either. I run 4.56's and 35's and the trans will still "hunt" for gears at least on an incline. I wish i would have gone with 4.88's at a minimum. When i do regear i will be going with 5.13's instead.
 
So the napa 447 is an adapter that will go between the 14bff joint and the rear driveshaft? Assume I can just slide the driveshaft back to fit the adapter in?

I didnt know that the 4.10s would be hunting for gears, I guess I didnt do as much research as I thot I had.
 
Artemis Entreri said:
So the napa 447 is an adapter that will go between the 14bff joint and the rear driveshaft? Assume I can just slide the driveshaft back to fit the adapter in?

I didnt know that the 4.10s would be hunting for gears, I guess I didnt do as much research as I thot I had.
Click to expand...

The 447 is not an adapter but rather a conversion joint, basically it is one size for the driveshaft and a different size for the differential. You'll probably have to remove the driveshaft in order to replace the u-joint unless you have one of those portable u-joint presses and even then alot easier to remove it and do it on a bench.
 
How much of a different size is it supposed to be? I mean, my rear one (14bff to the orig driveshaft) looks like it went together fine. I'm not disagreeing with all of you, I am going to try and buy the part tomorrow just curious how different the size is.
 
Artemis Entreri said:
How much of a different size is it supposed to be? I mean, my rear one (14bff to the orig driveshaft) looks like it went together fine. I'm not disagreeing with all of you, I am going to try and buy the part tomorrow just curious how different the size is.
Click to expand...

A 1330 U-joint has two different size caps, two are 1.0625" and the opposite two are 1.125". A 1350 U-joint uses all four caps the same size and the caps are 1.1875". The cros on both the 1330 and the 1350 are the same with a measurement of 3.625"
 
It's true. The stock U-joint "looks" like it fits, but it is too small in the axle yoke. When you drive it rattles around. I confirm #447 from NAPA is what you want. This will probably fix all of your problems. 4.10 and 35" is not too bad. It may hunt between 3rd and 4th at certain highway speeds, but 700s did that from the factory. If it can't choose, just put the gear selector in 3 until you reach higher speeds. Beyond that, the governor and/or 3-4 valve can be modified to help remedy the gear hunting, should you deem it neccesary.
 
Thanks, didnt make it to napa today, woke up with a killer headache and ive got to leave for work soon.

What is the governor exactly? And how does one go about fixing it to not hunt for gears?


Thanks all, really, I appreciate it.
-Steve-
 
The governor is the transmissions measurement of vehicle speed. By changing the weights and/or springs, you change all of the shift speeds to be higher or lower. The advantage of working with it is that it can be easily removed with the transmission in place. You can also modify the valve body to reduce gear hunting, but that is more work and more $$.
 
I've got a '90 K5 with 35's and 3.42s. It won't pull Granny off the pot, and really falls off with a head wind or slight uphill grade and downshifts. I was hoping going with 4.10s would really help, but it doesn't sound like it. This is a daily driver that doesn't see a lot of off-roading. Dallas is fairly flat, not a bunch of hills. Anybody know if 4.10s work good around here with 35's and overdrive? Or do I need to look for something deeper?
 
4.56 is probably ideal, but switching from 3.42 to 4.10 will be a huge night/day difference. The advantage to 4.10 is that you can find stock axles with these gears. There have been lots of threads on this and people will generally recommend 4.56 or even 4.88. I run 4.10s with 700R4 and 35's with good results.
 
Well I went and ordered the part, going to have to wait till monday to get it, so that sucks, but oh well, thanks alot guys, any advice for when I go to put it in?
 
4x4high:

1310 is what most 4x4 1/2 ton u joints are. I believe they are 3"? across and 1 1/16" cap. Unless He's got 5 lug 1/2 ton rear and/or driveline, he wont need a 1330.

1350's would be correct for the 14 bolt, with a 3 1/4"? lockup across and a 1 3/16" cap

A 1330 isnt a conversion joint, it has a cap size of a 1310, but the width of a 1350. It is equal on all 4 corners. It also used on the 5 lug rears at the diff.

The above holds true in SPICER parts, cant imagine why it would be different in other apps.
 
Last edited:
Went to Napa, ordered the part number 447, should be there monday, so hopefully that should get done monday.

How do I know which ends go in the rear and which go in the driveshaft? Looked like it fit together to me before hand, lol.
 
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