NP205 grinding on deceleration....

[lowharley]

twin sticked 205 with th350. Dont hear it on acceleration, left off the gas and it starts griding, hit the gas back down and it hit hards but then quits until I let off again. then when I put it in a bind and spinning the tires it will bang pretty hard ever few rounds of the tire. Transmission has been rebuilt and I have been thru the rear axle (14 bolt) and all seems good. Never been into one of these cases and was curious to what it could be. Any ideas?

[jpmassey]

It could be several different problems. My guess is bad bearing letting the gears out of alignment (thus the 'bang'). They are really easy to work on and a full rebuild kit is only about $170.
I bet if you dig into it, you'll find the problem quickly.

[sas'd96TAHOE]

How much lift you got on the truck? Might be your pinion angle. My Tahoe did the EXACT same thing, threw in an axle shim and bam problem solved.

[ramburger]

pinion angle

had same chit happen to me, EXACT same symptoms

[lowharley]

cj7 with 106 wheelbase. combination of front/rear stretch. angle doesnt look to bad.

[sas'd96TAHOE]

Originally Posted by lowharley

cj7 with 106 wheelbase. combination of front/rear stretch. angle doesnt look to bad.

looks can be deceiving. My truck had the EXACT to the 't' noise/vibration happening. After lots of searching, i found out that it was my pinion angle causing it. I didn;t think it was tooooooo bad, but I put 6* shims in and the noise was gone instantly. they're only 30 bucks...

[lowharley]

If you are talking about the angle on the axle, the pinion was rotated up when the rear end was installed. There is no angle at the axle, points straight toward the tcase.

[ballardmotorsports]

Originally Posted by lowharley

If you are talking about the angle on the axle, the pinion was rotated up when the rear end was installed. There is no angle at the axle, points straight toward the tcase.

pinion angle my cj7 is 110" had a 205 and had this problem and swapped to a atlas 4 speed and still have some noise and vibration

[lowharley]

Does your driveshaft have a single joint or CV joint at the tcase?

[poorboy1]

Originally Posted by lowharley

Does your driveshaft have a single joint or CV joint at the tcase?

This.....if no cv then your axle should not point straight at tcase.

[lowharley]

Took the case apart. There is a crack in the 205/th350 adapter but the bearings appear good. The selector gear (that moves with the shift forks) for the rear has very slight damage to the teeth on one side but the gear it comes in contact with is intact and looks fine. The twin stick kit looks like some homeade brew. thinking the shift forks is not lining up just right because of the mods to the shift rails. Can see where they had been grinding on them.

[mountainguyed67]

U-joint angle,if no CV they need to be matched. I lifted A truck and had the same problem. Had the transfer case rebuilt and no change. Many years later,I was told it was the U-joint angle and addressed the problem. The problem went away.

[sjracer]

Originally Posted by lowharley

Took the case apart. There is a crack in the 205/th350 adapter but the bearings appear good. The selector gear (that moves with the shift forks) for the rear has very slight damage to the teeth on one side but the gear it comes in contact with is intact and looks fine. The twin stick kit looks like some homeade brew. thinking the shift forks is not lining up just right because of the mods to the shift rails. Can see where they had been grinding on them.

they are really common to crack at the adapter (a good machine shop can weld this but it's not cheap and if not done right can crack again), but i can guarantee that isn't your problem. gotta agree with the consensus. pinion angle is critical that it is matched on a non-cv shaft. the trans output angle is supposed to be (i think) within 2* of the pinion. there is better info on driveshaft tech here on pirate. also, like i've said here before, 205's don't need to be modded to twin stick, they can do it in stock form and have none of these type of problems that you described above. the only ability that you get by grinding the rails is the ability to do a front only dig, and i don't really see the point in that one.

[lowharley]

Appreciate the info. Looking for a replacement adapter, ordered a new seal/gasket kit while I have it out. Gonna clean it up and put it back in. Looks like the u joint caps are spinning, gonna replace the straps. Probably gonna get a cv shaft built.

[sjracer]

you might want to look into a flange style 205 ouput shaft for your cv. check jb conversions- they carry them for a 205. if you decide to get one make sure to order the seal at the same time.