Front drive shaft is hitting

[John Reason]

Guys thanks for all your input. I'll start with some new mounts and see if that helps it if not they need to be changed anyways Would you recommend a poly mount or the factory style rubber? I'll measure but the lift looks like a 4" lift.

 

[PrairieDrifter]

Guys thanks for all your input. I'll start with some new mounts and see if that helps it if not they need to be changed anyways Would you recommend a poly mount or the factory style rubber? I'll measure but the lift looks like a 4" lift.

I would recommend a poly mount. Poly is the way to go these days, I got mine from ord along with my motor mounts and suspension bushings, and I got body bushings from energy suspension. All my stuff is poly except for rear suspension cuz I haven’t got to it yet lol

 

[Frankenchevy]

That may be the wrong cross member under it. Iirc, the later half tons got the asymmetrical trans mount, that dipped down below the front shaft, and went above the exhaust on the opposite side. That one looks like the one ton version.

I thought you were on the right track until @bucket chimed in. Looks like my crossmember. Haven’t looked at it in a long while, though. Those trans mounts even look similar, which I thought were th400/k30 specific. But I’m a noob so...

Op, has the TC support rod I need!

 

[shiftpro]

Guys thanks for all your input. I'll start with some new mounts and see if that helps it if not they need to be changed anyways Would you recommend a poly mount or the factory style rubber? I'll measure but the lift looks like a 4" lift.

Don't sweat it. The rubber one has lasted only 35 years or so. Whatever is easiest for you to get. Even a wrecking yard. Might just be a bin full you can pick through.

 

[rpcraft]

You can get new rubber mounts online from all the etailers... I would recomend getting some of the poly ones for the transmission though, especially since it looks like he has a lot of leakage going on.

 

[Costjohj]

I had a similar issue when i put in 2" lift springs up front. I turned to a simple drive shaft spacer (bewteen the output yoke and shaft), which moved the DS 1" forward, clearing the cross member.

 

[rpcraft]

I had a similar issue when i put in 2" lift springs up front. I turned to a simple drive shaft spacer (bewteen the output yoke and shaft), which moved the DS 1" forward, clearing the cross member.

That is a good recommendation. Alternatively how often is the 4wd being used right now? I mean, if not needed right now just put it in 2 HI and unlock the front hubs? Obviously not a permanent solution but I just ask in case you are not thinking of the available cheap option. ;o)

 

[highdesertrange]

I can't put my finger on it but something is not right. with a 4 inch lift you shouldn't need spacers between the frame and the cross member. the mounts are diffidently oil soaked I would start there. also that hardware for the cross member looks shaky. different length bolts and the front washer is deformed and the nuts appear to be non-locking.

 

[PrairieDrifter]

I can't put my finger on it but something is not right. with a 4 inch lift you shouldn't need spacers between the frame and the cross member. the mounts are diffidently oil soaked I would start there. also that hardware for the cross member looks shaky. different length bolts and the front washer is deformed and the nuts appear to be non-locking.

I’ve got a 4 inch suspension lift, no spacers needed, my driveshaft clears with a little to spare, the nubs on the cardan joint are close to touching but they don’t make contact at full flex, so that’s all good. Spacing the crossmember down is usually not a preferred method.

I have it setup like factory, crossmember straight to the frame and the spacers go on the bottom side of the crossmember. Pinion angle on the axles will affect your clearances slightly but not too drastic.

Also just my opinion but I never use lock nuts. Personally I kind of hate em, I’ve never had issues with a nut and bolt and a simple crush style lockwasher, and if you’re really worried about it put a dab of mild loctite on it and be done with it.

 

[rpcraft]

That may be the wrong cross member under it. Iirc, the later half tons got the asymmetrical trans mount, that dipped down below the front shaft, and went above the exhaust on the opposite side. That one looks like the one ton version.

That crossmember was the pre 85 version I think. There is a lot of debate on when it started being put in trucks and stopped. I think also it depended on if the vehicle had a th400 in it because the th400 at the time used a different adapter than the TH350 or 700r4. I think they changed originally when the 700R4 came out but then also changed again in around 1986 or 1987. Mine has the same crossmember (on a 1985) but only because I picked it out of a wrecking yard and it mated up with my long foot adapter. The previous owner did a bit of a parts scramble on the original parts so since I was doing an LS swap and swapping to a 1997'ish 4l60E it allowed me to use the original 4 bolt tailshaft T-case adapter and not have to do anything else weird with any other adapters.

 

[highdesertrange]

Prairie Drifter locking nuts are factory for that cross member. not Nylocks but locking nuts. highdesertranger

 

[K201979]

I have 4 inches of lift and front shaft was hitting under hard acceleration or big bumps before new trans mounts. Good after. Mine were worse than the op's tho.

 

[91Sasquatch]

I would check the motor mounts and the transmission mount. Might have a bad one.

 

[K201979]

I been needin to check engine mounts, just aint had a spare second. Ive got a driveline vibration that the trans mount helped but did not fix. Gonna get the light out n look for the culpret this weekend. Engine mounts are on the list as well as bell housing bolts.

 

[K201979]

Bellhousing bolts were loose and engine mounts were both shot. Driver side rubber was loose from the metal and passenger had almost no rubber left! What was there was crumbling out. Just went for a short ride but feels better already. Ill bet my vibration is gone. Ill update with and get some pics tomorro.